Add Cacao

.gitmodules

@@ -0,0 +1,3 @@
+[submodule "kiwi-java"]
+	path = kiwi-java
+	url = git@git.shadowfacts.net:shadowfacts/kiwi-java.git

build.gradle

@@ -2,6 +2,7 @@ plugins {
 	id "fabric-loom" version "0.5-SNAPSHOT"
 	id "maven-publish"
     id "org.jetbrains.kotlin.jvm" version "1.4.30"
+	id "com.github.johnrengelman.shadow" version "4.0.4"
 }
 
 sourceCompatibility = JavaVersion.VERSION_1_8
@@ -18,6 +19,7 @@ repositories {
 	maven {
 		url = "https://mod-buildcraft.com/maven"
 	}
+	jcenter()
 }
 
 dependencies {
@@ -35,6 +37,10 @@ dependencies {
 	modImplementation "alexiil.mc.lib:libblockattributes-all:${project.libblockattributes_version}"
 	include "alexiil.mc.lib:libblockattributes-core:${project.libblockattributes_version}"
 	include "alexiil.mc.lib:libblockattributes-items:${project.libblockattributes_version}"
+
+	shadow project(":kiwi-java")
+
+	testImplementation "org.junit.jupiter:junit-jupiter:${project.junit_version}"
 }
 
 processResources {

gradle.properties

@@ -13,3 +13,5 @@ fabric_version=0.30.0+1.16
 fabric_kotlin_version=1.4.30+build.2
 
 libblockattributes_version=0.8.5
+
+junit_version = 5.4.0

kiwi-java

@@ -0,0 +1 @@
+Subproject commit 1cbaea53d207f1e16c6e5ee2e6bf6e3c1440ac44

settings.gradle

@@ -8,3 +8,5 @@ pluginManagement {
         gradlePluginPortal()
     }
 }
+
+include("kiwi-java")

src/main/kotlin/net/shadowfacts/cacao/CacaoScreen.kt

@@ -0,0 +1,100 @@
+package net.shadowfacts.cacao
+
+import com.mojang.blaze3d.platform.GlStateManager
+import net.minecraft.client.gui.screen.Screen
+import net.minecraft.client.util.math.MatrixStack
+import net.minecraft.sound.SoundEvents
+import net.minecraft.text.LiteralText
+import net.shadowfacts.cacao.geometry.Point
+import net.shadowfacts.cacao.util.MouseButton
+import net.shadowfacts.cacao.util.RenderHelper
+import java.util.*
+
+/**
+ * This class serves as the bridge between Cacao and a Minecraft [Screen]. It renders Cacao [Window]s in Minecraft and
+ * sends input events from Minecraft back to Cacao objects.
+ *
+ * @author shadowfacts
+ */
+open class CacaoScreen: Screen(LiteralText("CacaoScreen")) {
+
+	// _windows is the internal, mutable object, since we only want it to by mutated by the add/removeWindow methods.
+	private val _windows = LinkedList<Window>()
+	/**
+	 * The list of windows that belong to this screen.
+	 * This list should never be modified directly, only by using the [addWindow]/[removeWindow] methods.
+	 */
+	val windows: List<Window> = _windows
+
+	/**
+	 * Adds the given window to this screen's window list.
+	 * By default, the new window is added at the tail of the window list, making it the active window.
+	 * Only the active window will receive input events.
+	 *
+	 * @param window The Window to add to this screen.
+	 * @param index The index to insert the window into the window list at.
+	 * @return The window that was added, as a convenience.
+	 */
+	fun <T: Window> addWindow(window: T, index: Int = _windows.size): T {
+		_windows.add(index, window)
+
+		window.screen = this
+		window.wasAdded()
+		window.resize(width, height)
+
+		return window
+	}
+
+	/**
+	 * Removes the given window from this screen's window list.
+	 */
+	fun removeWindow(window: Window) {
+		_windows.remove(window)
+	}
+
+	override fun init() {
+		super.init()
+
+		windows.forEach {
+			it.resize(width, height)
+		}
+	}
+
+	override fun render(matrixStack: MatrixStack, mouseX: Int, mouseY: Int, delta: Float) {
+		if (client != null) {
+			// workaround this.minecraft sometimes being null causing a crash
+			renderBackground(matrixStack)
+		}
+
+		val mouse = Point(mouseX, mouseY)
+		windows.forEach {
+			it.draw(matrixStack, mouse, delta)
+		}
+	}
+
+	override fun mouseClicked(mouseX: Double, mouseY: Double, button: Int): Boolean {
+		val window = windows.lastOrNull()
+		val result = window?.mouseClicked(Point(mouseX, mouseY), MouseButton.fromMC(button))
+		return if (result == true) {
+			RenderHelper.playSound(SoundEvents.UI_BUTTON_CLICK)
+			true
+		} else {
+			false
+		}
+	}
+
+	override fun mouseDragged(mouseX: Double, mouseY: Double, button: Int, deltaX: Double, deltaY: Double): Boolean {
+		val window = windows.lastOrNull()
+		val startPoint = Point(mouseX, mouseY)
+		val delta = Point(deltaX, deltaY)
+		val result = window?.mouseDragged(startPoint, delta, MouseButton.fromMC(button))
+		return result == true
+	}
+
+	override fun mouseReleased(mouseX: Double, mouseY: Double, button: Int): Boolean {
+		val window = windows.lastOrNull()
+		val result = window?.mouseReleased(Point(mouseX, mouseY), MouseButton.fromMC(button))
+		return result == true
+	}
+
+}

src/main/kotlin/net/shadowfacts/cacao/LayoutVariable.kt

@@ -0,0 +1,18 @@
+package net.shadowfacts.cacao
+
+import net.shadowfacts.cacao.view.View
+import no.birkett.kiwi.Variable
+
+/**
+ * A Kiwi variable that belongs to a Cacao view.
+ * This class generally isn't used directly, but via the anchor *Anchor properties on [View].
+ *
+ * @author shadowfacts
+ */
+class LayoutVariable(val owner: View, val property: String): Variable("LayoutVariable") {
+
+	override fun getName() = "$owner.$property"
+
+	override fun toString() = "LayoutVariable(name=$name, value=$value)"
+
+}

src/main/kotlin/net/shadowfacts/cacao/README.md

@@ -0,0 +1,33 @@
+# Cacao
+Cacao is a UI framework for Fabric/Minecraft mods based on Apple's [Cocoa](https://en.wikipedia.org/wiki/Cocoa_(API)
+UI toolkit.
+
+## Architecture
+### Screen
+A [CacaoScreen][] is the object that acts as the interface between Minecraft GUI code and the Cacao framework.
+
+The CacaoScreen draws Cacao views on screen and passes Minecraft input events to the appropriate Views. The CacaoScreen
+owns a group of [Window](#window) objects which are displayed on screen, one on top of the other.
+
+[CacaoScreen]: https://git.shadowfacts.net/minecraft/ASMR/src/branch/master/src/main/kotlin/net/shadowfacts/cacao/CacaoScreen.kt
+
+### Window
+A [Window][] object has a root [View Controller](#view-controller) that it displays on screen.
+
+The Window occupies the entire screen space and translates events from the screen to the root View Controller's View.
+It owns a Solver object that manages layout constraints. The window also handles screen resizing and re-lays out the
+view hierarchy.
+
+[Window]: https://git.shadowfacts.net/minecraft/ASMR/src/branch/master/src/main/kotlin/net/shadowfacts/cacao/Window.kt
+
+### View Controller
+A [ViewController][] object owns a view, receives lifecycle events for it, and is generally used to control the view.
+
+Each View Controller has a single root [View](#view) which in turn may have subviews.
+
+[ViewController]: https://git.shadowfacts.net/minecraft/ASMR/src/branch/master/src/main/kotlin/net/shadowfacts/cacao/viewcontroller/ViewController.kt
+
+### View
+A [View][] object represents a single view on screen. It handles drawing, positioning, and directly handles input. 
+
+[View]: https://git.shadowfacts.net/minecraft/ASMR/src/branch/master/src/main/kotlin/net/shadowfacts/cacao/view/View.kt

src/main/kotlin/net/shadowfacts/cacao/Window.kt

@@ -0,0 +1,214 @@
+package net.shadowfacts.cacao
+
+import net.minecraft.client.util.math.MatrixStack
+import net.shadowfacts.cacao.geometry.Point
+import net.shadowfacts.cacao.util.MouseButton
+import net.shadowfacts.cacao.view.View
+import net.shadowfacts.cacao.viewcontroller.ViewController
+import net.shadowfacts.kiwidsl.dsl
+import no.birkett.kiwi.Constraint
+import no.birkett.kiwi.Solver
+import no.birkett.kiwi.Variable
+
+/**
+ * A Window is the object at the top of a Cacao view hierarchy. It occupies the entirety of the Minecraft screen size
+ * and provides the base coordinate system for its view hierarchy.
+ *
+ * The Window owns the Kiwi [Solver] object used for layout by all of its views.
+ *
+ * @author shadowfacts
+ *
+ * @param viewController The root view controller for this window.
+ */
+class Window(
+		/**
+		 * The root view controller for this window.
+		 */
+		val viewController: ViewController
+) {
+
+	/**
+	 * The screen that this window belongs to.
+	 * Not initialized until this window is added to a screen, using it before that point will throw a runtime exception.
+	 */
+	lateinit var screen: CacaoScreen
+
+	/**
+	 * The constraint solver used by this window and all its views and subviews.
+	 */
+	var solver = Solver()
+
+	/**
+	 * Layout anchor for the left edge of this view in the window's coordinate system.
+	 */
+	val leftAnchor = Variable("left")
+	/**
+	 * Layout anchor for the right edge of this view in the window's coordinate system.
+	 */
+	val rightAnchor = Variable("right")
+	/**
+	 * Layout anchor for the top edge of this view in the window's coordinate system.
+	 */
+	val topAnchor = Variable("top")
+	/**
+	 * Layout anchor for the bottom edge of this view in the window's coordinate system.
+	 */
+	val bottomAnchor = Variable("bottom")
+	/**
+	 * Layout anchor for the width of this view in the window's coordinate system.
+	 */
+	val widthAnchor = Variable("width")
+	/**
+	 * Layout anchor for the height of this view in the window's coordinate system.
+	 */
+	val heightAnchor = Variable("height")
+	/**
+	 * Layout anchor for the center X position of this view in the window's coordinate system.
+	 */
+	val centerXAnchor = Variable("centerX")
+	/**
+	 * Layout anchor for the center Y position of this view in the window's coordinate system.
+	 */
+	val centerYAnchor = Variable("centerY")
+
+	// internal constraints that specify the window size based on the MC screen size
+	// stored so that they can be removed when the screen is resized
+	private var widthConstraint: Constraint? = null
+	private var heightConstraint: Constraint? = null
+
+	private var currentDragReceiver: View? = null
+
+	init {
+		createInternalConstraints()
+	}
+
+	fun wasAdded() {
+		viewController.window = this
+		viewController.loadView()
+
+		viewController.view.window = this
+		viewController.view.solver = solver
+		viewController.view.wasAdded()
+		viewController.createConstraints {
+			viewController.view.leftAnchor equalTo leftAnchor
+			viewController.view.rightAnchor equalTo rightAnchor
+			viewController.view.topAnchor equalTo topAnchor
+			viewController.view.bottomAnchor equalTo bottomAnchor
+		}
+
+		viewController.viewDidLoad()
+
+		layout()
+	}
+
+	/**
+	 * Creates the internal constraints used by the window.
+	 * If overridden, the super-class method must be called.
+	 */
+	protected fun createInternalConstraints() {
+		solver.dsl {
+			leftAnchor equalTo 0
+			topAnchor equalTo 0
+
+			rightAnchor equalTo (leftAnchor + widthAnchor)
+			bottomAnchor equalTo (topAnchor + heightAnchor)
+			centerXAnchor equalTo (leftAnchor + widthAnchor / 2)
+			centerYAnchor equalTo (topAnchor + heightAnchor / 2)
+		}
+	}
+
+	/**
+	 * Called by the window's [screen] when the Minecraft screen is resized.
+	 * Used to update the window's width and height constraints and re-layout views.
+	 */
+	internal fun resize(width: Int, height: Int) {
+		if (widthConstraint != null) solver.removeConstraint(widthConstraint)
+		if (heightConstraint != null) solver.removeConstraint(heightConstraint)
+		solver.dsl {
+			widthConstraint = (widthAnchor equalTo width)
+			heightConstraint = (heightAnchor equalTo height)
+		}
+		layout()
+	}
+
+	/**
+	 * Convenience method that removes this window from its [screen].
+	 */
+	fun removeFromScreen() {
+		viewController.viewWillDisappear()
+		screen.removeWindow(this)
+		viewController.viewDidDisappear()
+	}
+
+	/**
+	 * Instructs the solver to solve all of the provided constraints.
+	 * Should be called after the view hierarchy is setup.
+	 */
+	fun layout() {
+		viewController.viewWillLayoutSubviews()
+		solver.updateVariables()
+		viewController.viewDidLayoutSubviews()
+	}
+
+	/**
+	 * Draws this window and all of its views.
+	 * This method is called by [CacaoScreen] and generally shouldn't be called directly.
+	 *
+	 * @param mouse The point in the coordinate system of the window.
+	 * @param delta The time elapsed since the last frame.
+	 */
+	fun draw(matrixStack: MatrixStack, mouse: Point, delta: Float) {
+		val mouseInView = Point(mouse.x - viewController.view.frame.left, mouse.y - viewController.view.frame.top)
+		viewController.view.draw(matrixStack, mouseInView, delta)
+	}
+
+	/**
+	 * Called when a mouse button is clicked and this is the active window.
+	 * This method is called by [CacaoScreen] and generally shouldn't be called directly.
+	 *
+	 * @param point The point in the window of the click.
+	 * @param mouseButton The mouse button that was used to click.
+	 * @return Whether the mouse click was handled by a view.
+	 */
+	fun mouseClicked(point: Point, mouseButton: MouseButton): Boolean {
+		if (point in viewController.view.frame) {
+			val mouseInView = Point(point.x - viewController.view.frame.left, point.y - viewController.view.frame.top)
+			return viewController.view.mouseClicked(mouseInView, mouseButton)
+		} else {
+			// remove the window from the screen when the mouse clicks outside the window and this is not the primary window
+			if (screen.windows.size > 1) {
+				removeFromScreen()
+			}
+		}
+		return false
+	}
+
+	fun mouseDragged(startPoint: Point, delta: Point, mouseButton: MouseButton): Boolean {
+		val currentlyDraggedView = this.currentDragReceiver
+		if (currentlyDraggedView != null) {
+			return currentlyDraggedView.mouseDragged(startPoint, delta, mouseButton)
+		} else if (startPoint in viewController.view.frame) {
+			val startInView = Point(startPoint.x - viewController.view.frame.left, startPoint.y - viewController.view.frame.top)
+			var prevView: View? = null
+			var view = viewController.view.subviewsAtPoint(startInView).maxBy(View::zIndex)
+			while (view != null && !view.respondsToDragging) {
+				prevView = view
+				val pointInView = viewController.view.convert(startInView, to = view)
+				view = view.subviewsAtPoint(pointInView).maxBy(View::zIndex)
+			}
+			this.currentDragReceiver = view ?: prevView
+			return this.currentDragReceiver?.mouseDragged(startPoint, delta, mouseButton) ?: false
+		}
+		return false
+	}
+
+	fun mouseReleased(point: Point, mouseButton: MouseButton): Boolean {
+		val currentlyDraggedView = this.currentDragReceiver
+		if (currentlyDraggedView != null) {
+			this.currentDragReceiver = null
+			return true
+		}
+		return false
+	}
+
+}

src/main/kotlin/net/shadowfacts/cacao/geometry/Axis.kt

@@ -0,0 +1,19 @@
+package net.shadowfacts.cacao.geometry
+
+/**
+ * An axis in a 2D coordinate plane.
+ *
+ * @author shadowfacts
+ */
+enum class Axis {
+	HORIZONTAL, VERTICAL;
+
+	/**
+	 * Gets the axis that is perpendicular to this one.
+	 */
+	val perpendicular: Axis
+		get() = when (this) {
+			HORIZONTAL -> VERTICAL
+			VERTICAL -> HORIZONTAL
+		}
+}

src/main/kotlin/net/shadowfacts/cacao/geometry/AxisPosition.kt

@@ -0,0 +1,21 @@
+package net.shadowfacts.cacao.geometry
+
+/**
+ * A relative position on a line along an axis.
+ *
+ * @author shadowfacts
+ */
+enum class AxisPosition {
+	/**
+	 * Top for vertical, left for horizontal.
+	 */
+	LEADING,
+	/**
+	 * Center X/Y.
+	 */
+	CENTER,
+	/**
+	 * Bottom for vertical, right for horizontal.
+	 */
+	TRAILING;
+}

src/main/kotlin/net/shadowfacts/cacao/geometry/BezierCurve.kt

@@ -0,0 +1,49 @@
+package net.shadowfacts.cacao.geometry
+
+import java.lang.RuntimeException
+import kotlin.math.pow
+
+/**
+ * Helper class that represents a cubic bezier curve.
+ *
+ * @author shadowfacts
+ */
+data class BezierCurve(private val points: Array<Point>) {
+
+	init {
+		if (points.size != 4) {
+			throw RuntimeException("Cubic bezier curve must have exactly four points")
+		}
+	}
+
+	fun point(time: Double): Point {
+		val x = coordinate(time, Axis.HORIZONTAL)
+		val y = coordinate(time, Axis.VERTICAL)
+		return Point(x, y)
+	}
+
+	private fun coordinate(t: Double, axis: Axis): Double {
+		// B(t)=(1-t)^3*p0+3(1-t)^2*t*p1+3(1-t)*t^2*p2+t^3*p3
+		val p0 = points[0][axis]
+		val p1 = points[1][axis]
+		val p2 = points[2][axis]
+		val p3 = points[3][axis]
+		return ((1 - t).pow(3) * p0) + (3 * (1 - t).pow(2) * t * p1) + (3 * (1 - t) * t.pow(2) * p2) + (t.pow(3) * p3)
+	}
+
+	override fun equals(other: Any?): Boolean {
+		if (this === other) return true
+		if (javaClass != other?.javaClass) return false
+
+		other as BezierCurve
+
+		if (!points.contentEquals(other.points)) return false
+
+		return true
+	}
+
+	override fun hashCode(): Int {
+		return points.contentHashCode()
+	}
+
+}

src/main/kotlin/net/shadowfacts/cacao/geometry/Point.kt

@@ -0,0 +1,31 @@
+package net.shadowfacts.cacao.geometry
+
+/**
+ * Helper class for defining 2D points.
+ *
+ * @author shadowfacts
+ */
+data class Point(val x: Double, val y: Double) {
+
+	constructor(x: Int, y: Int): this(x.toDouble(), y.toDouble())
+
+	companion object {
+		val ORIGIN = Point(0.0, 0.0)
+	}
+
+	operator fun plus(other: Point): Point {
+		return Point(x + other.x, y + other.y)
+	}
+
+	operator fun minus(other: Point): Point {
+		return Point(x - other.x, y - other.y)
+	}
+
+	operator fun get(axis: Axis): Double {
+		return when (axis) {
+			Axis.HORIZONTAL -> x
+			Axis.VERTICAL -> y
+		}
+	}
+
+}

src/main/kotlin/net/shadowfacts/cacao/geometry/Rect.kt

@@ -0,0 +1,41 @@
+package net.shadowfacts.cacao.geometry
+
+/**
+ * Helper class for defining rectangles. Provides helper values for calculating perpendicular components of a rectangle based on X/Y/W/H.
+ *
+ * @author shadowfacts
+ */
+data class Rect(val left: Double, val top: Double, val width: Double, val height: Double) {
+
+	constructor(origin: Point, size: Size): this(origin.x, origin.y, size.width, size.height)
+
+	val right: Double by lazy {
+		left + width
+	}
+	val bottom: Double by lazy {
+		top + height
+	}
+
+	val midX: Double by lazy {
+		left + width / 2
+	}
+	val midY: Double by lazy {
+		top + height / 2
+	}
+
+	val origin: Point by lazy {
+		Point(left, top)
+	}
+	val center: Point by lazy {
+		Point(midX, midY)
+	}
+
+	val size: Size by lazy {
+		Size(width, height)
+	}
+
+	operator fun contains(point: Point): Boolean {
+		return point.x in left..right && point.y in top..bottom
+	}
+
+}

src/main/kotlin/net/shadowfacts/cacao/geometry/Size.kt

@@ -0,0 +1,8 @@
+package net.shadowfacts.cacao.geometry
+
+/**
+ * Helper class for specifying the size of objects.
+ *
+ * @author shadowfacts
+ */
+data class Size(val width: Double, val height: Double)

src/main/kotlin/net/shadowfacts/cacao/util/Color.kt

@@ -0,0 +1,34 @@
+package net.shadowfacts.cacao.util
+
+/**
+ * Helper class for Cacao colors.
+ *
+ * @author shadowfacts
+ * @param red The red component, from 0-255.
+ * @param green The green component, from 0-255.
+ * @param blue The blue component, from 0-255.
+ * @param alpha The alpha (i.e. transparency) component, from 0-255. (0 is transparent, 255 is opaque)
+ */
+data class Color(val red: Int, val green: Int, val blue: Int, val alpha: Int = 255) {
+
+	/**
+	 * Constructs a color from the packed RGB color.
+	 */
+	constructor(rgb: Int, alpha: Int = 255): this(rgb shr 16, (rgb shr 8) and 255, rgb and 255, alpha)
+
+	/**
+	 * The ARGB packed representation of this color.
+	 */
+	val argb: Int
+		get() = ((alpha and 255) shl 24) or ((red and 255) shl 16) or ((green and 255) shl 8) or (blue and 255)
+
+	companion object {
+		val CLEAR = Color(0, alpha = 0)
+		val WHITE = Color(0xffffff)
+		val BLACK = Color(0)
+		val RED = Color(0xff0000)
+		val GREEN = Color(0x00ff00)
+		val BLUE = Color(0x0000ff)
+	}
+
+}

src/main/kotlin/net/shadowfacts/cacao/util/EnumHelper.kt

@@ -0,0 +1,20 @@
+package net.shadowfacts.cacao.util
+
+/**
+ * @author shadowfacts
+ */
+object EnumHelper {
+
+	fun <E: Enum<E>> next(value: E): E {
+		val constants = value.declaringClass.enumConstants
+		val index = constants.indexOf(value) + 1
+		return if (index < constants.size) constants[index] else constants.first()
+	}
+
+	fun <E: Enum<E>> previous(value: E): E {
+		val constants = value.declaringClass.enumConstants
+		val index = constants.indexOf(value) - 1
+		return if (index >= 0) constants[index] else constants.last()
+	}
+
+}

src/main/kotlin/net/shadowfacts/cacao/util/LowestCommonAncestor.kt

@@ -0,0 +1,56 @@
+package net.shadowfacts.cacao.util
+
+import java.util.*
+import kotlin.NoSuchElementException
+
+/**
+ * A linear time algorithm for finding the lowest common ancestor of two nodes in a graph.
+ * Based on https://stackoverflow.com/a/6342546/4731558
+ *
+ * Works be finding the path from each node back to the root node.
+ * The LCA will then be the node after which the paths diverge.
+ *
+ * @author shadowfacts
+ */
+object LowestCommonAncestor {
+
+	fun <Node> find(node1: Node, node2: Node, parent: Node.() -> Node?): Node? {
+		@Suppress("NAME_SHADOWING") var node1: Node? = node1
+		@Suppress("NAME_SHADOWING") var node2: Node? = node2
+
+		val parent1 = LinkedList<Node>()
+		while (node1 != null) {
+			parent1.push(node1)
+			node1 = node1.parent()
+		}
+
+		val parent2 = LinkedList<Node>()
+		while (node2 != null) {
+			parent2.push(node2)
+			node2 = node2.parent()
+		}
+
+		// paths don't converge on the same root element
+		if (parent1.first != parent2.first) {
+			return null
+		}
+
+		var oldNode: Node? = null
+		while (node1 == node2 && parent1.isNotEmpty() && parent2.isNotEmpty()) {
+			oldNode = node1
+			node1 = parent1.popOrNull()
+			node2 = parent2.popOrNull()
+		}
+		return if (node1 == node2) node1!!
+		else oldNode!!
+	}
+
+}
+
+private fun <T> LinkedList<T>.popOrNull(): T? {
+	return try {
+		pop()
+	} catch (e: NoSuchElementException) {
+		null
+	}
+}

src/main/kotlin/net/shadowfacts/cacao/util/MouseButton.kt

@@ -0,0 +1,19 @@
+package net.shadowfacts.cacao.util
+
+/**
+ * @author shadowfacts
+ */
+enum class MouseButton {
+	LEFT, RIGHT, MIDDLE, UNKNOWN;
+
+	companion object {
+		fun fromMC(button: Int): MouseButton {
+			return when (button) {
+				0 -> LEFT
+				1 -> RIGHT
+				2 -> MIDDLE
+				else -> UNKNOWN
+			}
+		}
+	}
+}

src/main/kotlin/net/shadowfacts/cacao/util/RenderHelper.kt

@@ -0,0 +1,130 @@
+package net.shadowfacts.cacao.util
+
+import com.mojang.blaze3d.platform.GlStateManager
+import com.mojang.blaze3d.systems.RenderSystem
+import net.minecraft.client.MinecraftClient
+import net.minecraft.client.gui.DrawableHelper
+import net.minecraft.client.render.*
+import net.minecraft.client.sound.PositionedSoundInstance
+import net.minecraft.client.util.math.MatrixStack
+import net.minecraft.sound.SoundEvent
+import net.shadowfacts.cacao.geometry.Point
+import net.shadowfacts.cacao.geometry.Rect
+import net.shadowfacts.cacao.util.texture.Texture
+import org.lwjgl.opengl.GL11
+
+/**
+ * Helper methods for rendering using Minecraft's utilities from Cacao views.
+ * For unit testing, all drawing and OpenGL interaction can be disabled by setting the `cacao.drawing.disabled` JVM property to `true`.
+ *
+ * @author shadowfacts
+ */
+object RenderHelper {
+
+	val disabled = (System.getProperty("cacao.drawing.disabled") ?: "false").toBoolean()
+
+	// TODO: find a better place for this
+	fun playSound(event: SoundEvent) {
+		if (disabled) return
+		MinecraftClient.getInstance().soundManager.play(PositionedSoundInstance.master(event, 1f))
+	}
+
+	/**
+	 * Draws a solid [rect] filled with the given [color].
+	 */
+	fun fill(matrixStack: MatrixStack, rect: Rect, color: Color) {
+		if (disabled) return
+		DrawableHelper.fill(matrixStack, rect.left.toInt(), rect.top.toInt(), rect.right.toInt(), rect.bottom.toInt(), color.argb)
+	}
+
+	/**
+	 * Binds and draws the given [texture] filling the [rect].
+	 */
+	fun draw(rect: Rect, texture: Texture) {
+		if (disabled) return
+		color(1f, 1f, 1f, 1f)
+		MinecraftClient.getInstance().textureManager.bindTexture(texture.location)
+		draw(rect.left, rect.top, texture.u, texture.v, rect.width, rect.height, texture.width, texture.height)
+	}
+
+	fun drawLine(start: Point, end: Point, z: Double, width: Float, color: Color) {
+		if (disabled) return
+
+		GlStateManager.lineWidth(width)
+		val tessellator = Tessellator.getInstance()
+		val buffer = tessellator.buffer
+		buffer.begin(GL11.GL_LINES, VertexFormats.POSITION_COLOR)
+		buffer.vertex(start.x, start.y, z).color(color).next()
+		buffer.vertex(end.x, end.y, z).color(color).next()
+		tessellator.draw()
+	}
+
+	/**
+	 * Draws the bound texture with the given screen and texture position and size.
+	 */
+	fun draw(x: Double, y: Double, u: Int, v: Int, width: Double, height: Double, textureWidth: Int, textureHeight: Int) {
+		if (disabled) return
+		val uStart = u.toFloat() / textureWidth
+		val uEnd = (u + width).toFloat() / textureWidth
+		val vStart = v.toFloat() / textureHeight
+		val vEnd = (v + height).toFloat() / textureHeight
+		drawTexturedQuad(x, x + width, y, y + height, 0.0, uStart, uEnd, vStart, vEnd)
+	}
+
+	// Copied from net.minecraft.client.gui.DrawableHelper
+	private fun drawTexturedQuad(xStart: Double, xEnd: Double, yStart: Double, yEnd: Double, z: Double, uStart: Float, uEnd: Float, vStart: Float, vEnd: Float) {
+		val tessellator = Tessellator.getInstance()
+		val buffer = tessellator.buffer
+		buffer.begin(GL11.GL_QUADS, VertexFormats.POSITION_TEXTURE)
+		buffer.vertex(xStart, yEnd, z).texture(uStart, vEnd).next()
+		buffer.vertex(xEnd, yEnd, z).texture(uEnd, vEnd).next()
+		buffer.vertex(xEnd, yStart, z).texture(uEnd, vStart).next()
+		buffer.vertex(xStart, yStart, z).texture(uStart, vStart).next()
+		tessellator.draw()
+	}
+
+	/**
+	 * @see org.lwjgl.opengl.GL11.glPushMatrix
+	 */
+	fun pushMatrix() {
+		if (disabled) return
+		RenderSystem.pushMatrix()
+	}
+
+	/**
+	 * @see org.lwjgl.opengl.GL11.glPopMatrix
+	 */
+	fun popMatrix() {
+		if (disabled) return
+		RenderSystem.popMatrix()
+	}
+
+	/**
+	 * @see org.lwjgl.opengl.GL11.glTranslated
+	 */
+	fun translate(x: Double, y: Double, z: Double = 0.0) {
+		if (disabled) return
+		RenderSystem.translated(x, y, z)
+	}
+
+	/**
+	 * @see org.lwjgl.opengl.GL11.glScaled
+	 */
+	fun scale(x: Double, y: Double, z: Double = 1.0) {
+		if (disabled) return
+		RenderSystem.scaled(x, y, z)
+	}
+
+	/**
+	 * @see org.lwjgl.opengl.GL11.glColor4f
+	 */
+	fun color(r: Float, g: Float, b: Float, alpha: Float) {
+		if (disabled) return
+		RenderSystem.color4f(r, g, b, alpha)
+	}
+
+	private fun VertexConsumer.color(color: Color): VertexConsumer {
+		return color(color.red, color.green, color.blue, color.alpha)
+	}
+
+}

src/main/kotlin/net/shadowfacts/cacao/util/constraints.kt

@@ -0,0 +1,14 @@
+package net.shadowfacts.cacao.util
+
+import no.birkett.kiwi.Constraint
+import no.birkett.kiwi.Term
+import no.birkett.kiwi.Variable
+
+/**
+ * Gets all the variables used by this constraint.
+ *
+ * @author shadowfacts
+ */
+fun Constraint.getVariables(): List<Variable> {
+	return expression.terms.map(Term::getVariable)
+}

src/main/kotlin/net/shadowfacts/cacao/util/properties/ObservableLateInitProperty.kt

@@ -0,0 +1,24 @@
+package net.shadowfacts.cacao.util.properties
+
+import kotlin.reflect.KProperty
+
+/**
+ * @author shadowfacts
+ */
+class ObservableLateInitProperty<T: Any>(val observer: (T) -> Unit) {
+
+	lateinit var storage: T
+
+	val isInitialized: Boolean
+		get() = this::storage.isInitialized
+
+	operator fun getValue(thisRef: Any, property: KProperty<*>): T {
+		return storage
+	}
+
+	operator fun setValue(thisRef: Any, property: KProperty<*>, value: T) {
+		storage = value
+		observer(value)
+	}
+
+}

src/main/kotlin/net/shadowfacts/cacao/util/properties/ObservableLazyProperty.kt

@@ -0,0 +1,20 @@
+package net.shadowfacts.cacao.util.properties
+
+import kotlin.reflect.KProperty
+
+/**
+ * @author shadowfacts
+ */
+class ObservableLazyProperty<Value>(val create: () -> Value, val onCreate: () -> Unit) {
+
+	var storage: Value? = null
+
+	operator fun getValue(thisRef: Any, property: KProperty<*>): Value {
+		if (storage == null) {
+			storage = create()
+			onCreate()
+		}
+		return storage!!
+	}
+
+}

src/main/kotlin/net/shadowfacts/cacao/util/properties/ResettableLazyProperty.kt

@@ -0,0 +1,24 @@
+package net.shadowfacts.cacao.util.properties
+
+import kotlin.reflect.KProperty
+
+/**
+ * @author shadowfacts
+ */
+class ResettableLazyProperty<Value>(val initializer: () -> Value) {
+	var value: Value? = null
+
+	val isInitialized: Boolean
+		get() = value != null
+
+	operator fun getValue(thisRef: Any, property: KProperty<*>): Value {
+		if (value == null) {
+			value = initializer()
+		}
+		return value!!
+	}
+
+	fun reset() {
+		value = null
+	}
+}

src/main/kotlin/net/shadowfacts/cacao/util/texture/NinePatchTexture.kt

@@ -0,0 +1,61 @@
+package net.shadowfacts.cacao.util.texture
+
+import net.minecraft.util.Identifier
+
+/**
+ * Helper class that represents a texture that can be divided into nine pieces (4 corners, 4 edges, and the center)
+ * and can be drawn at any size by combining and repeating those pieces.
+ *
+ * It also provides convenience [Texture] objects that represent the different patches.
+ *
+ * @author shadowfacts
+ * @param texture The base [Texture] object.
+ * @param cornerWidth The width of each corner (and therefore the width of the vertical edges).
+ * @param cornerHeight The height of each corner (and therefore the height of the horizontal edges.)
+ * @param centerWidth The width of the center patch.
+ * @param centerHeight The height of the center patch.
+ */
+data class NinePatchTexture(val texture: Texture, val cornerWidth: Int, val cornerHeight: Int, val centerWidth: Int, val centerHeight: Int) {
+
+	companion object {
+		val PANEL_BG = NinePatchTexture(Texture(Identifier("textures/gui/demo_background.png"), 0, 0), 5, 5, 238, 156)
+
+		val BUTTON_BG = NinePatchTexture(Texture(Identifier("textures/gui/widgets.png"), 0, 66), 3, 3, 194, 14)
+		val BUTTON_HOVERED_BG = NinePatchTexture(Texture(Identifier("textures/gui/widgets.png"), 0, 86), 3, 3, 194, 14)
+		val BUTTON_DISABLED_BG = NinePatchTexture(Texture(Identifier("textures/gui/widgets.png"), 0, 46), 3, 3, 194, 14)
+	}
+
+	// Corners
+	val topLeft by lazy {
+		texture
+	}
+	val topRight by lazy {
+		Texture(texture.location, texture.u + cornerWidth + centerWidth, texture.v, texture.width, texture.height)
+	}
+	val bottomLeft by lazy {
+		Texture(texture.location, texture.u, texture.v + cornerHeight + centerHeight, texture.width, texture.height)
+	}
+	val bottomRight by lazy {
+		Texture(texture.location, topRight.u, bottomLeft.v, texture.width, texture.height)
+	}
+
+	// Edges
+	val topMiddle by lazy {
+		Texture(texture.location, texture.u + cornerWidth, texture.v, texture.width, texture.height)
+	}
+	val bottomMiddle by lazy {
+		Texture(texture.location, topMiddle.u, bottomLeft.v, texture.width, texture.height)
+	}
+	val leftMiddle by lazy {
+		Texture(texture.location, texture.u, texture.v + cornerHeight, texture.width, texture.height)
+	}
+	val rightMiddle by lazy {
+		Texture(texture.location, topRight.u, leftMiddle.v, texture.width, texture.height)
+	}
+
+	// Center
+	val center by lazy {
+		Texture(texture.location, texture.u + cornerWidth, texture.v + cornerHeight, texture.width, texture.height)
+	}
+
+}

src/main/kotlin/net/shadowfacts/cacao/util/texture/Texture.kt

@@ -0,0 +1,15 @@
+package net.shadowfacts.cacao.util.texture
+
+import net.minecraft.util.Identifier
+
+/**
+ * A helper class that represents a texture.
+ *
+ * @author shadowfacts
+ * @param location The identifier representing the resource-pack location of the texture image.
+ * @param u The X coordinate in pixels of where the texture starts within the image.
+ * @param v The Y coordinate in pixels of where the texture starts within the image.
+ * @param width The width in pixels of the entire image.
+ * @param height The height in pixels of the entire image.
+ */
+data class Texture(val location: Identifier, val u: Int, val v: Int, val width: Int = 256, val height: Int = 256)

src/main/kotlin/net/shadowfacts/cacao/view/BezierCurveView.kt

@@ -0,0 +1,36 @@
+package net.shadowfacts.cacao.view
+
+import net.minecraft.client.util.math.MatrixStack
+import net.shadowfacts.cacao.geometry.BezierCurve
+import net.shadowfacts.cacao.geometry.Point
+import net.shadowfacts.cacao.util.Color
+import net.shadowfacts.cacao.util.RenderHelper
+
+/**
+ * @author shadowfacts
+ */
+class BezierCurveView(val curve: BezierCurve): View() {
+
+	private val points by lazy {
+		val step = 0.05
+		var t = 0.0
+		val points = mutableListOf<Point>()
+		while (t <= 1) {
+			points.add(curve.point(t))
+			t += step
+		}
+		points
+	}
+
+	var lineWidth = 3f
+	var lineColor = Color.BLACK
+
+	override fun drawContent(matrixStack: MatrixStack, mouse: Point, delta: Float) {
+		RenderHelper.scale(bounds.width, bounds.height)
+		for ((index, point) in points.withIndex()) {
+			val next = points.getOrNull(index + 1) ?: break
+			RenderHelper.drawLine(point, next, zIndex, lineWidth, lineColor)
+		}
+	}
+
+}

src/main/kotlin/net/shadowfacts/cacao/view/DialogView.kt

@@ -0,0 +1,114 @@
+package net.shadowfacts.cacao.view
+
+import net.shadowfacts.cacao.Window
+import net.shadowfacts.cacao.geometry.Axis
+import net.shadowfacts.cacao.util.Color
+import net.shadowfacts.cacao.util.texture.NinePatchTexture
+import net.shadowfacts.cacao.util.texture.Texture
+import net.shadowfacts.cacao.view.button.Button
+import net.shadowfacts.kiwidsl.dsl
+
+/**
+ * @author shadowfacts
+ */
+class DialogView(
+		val title: String,
+		val message: String,
+		val buttonTypes: Array<ButtonType>,
+		val iconTexture: Texture?,
+		val buttonCallback: (ButtonType, Window) -> Unit
+): View() {
+
+	interface ButtonType {
+		val localizedName: String
+	}
+
+	enum class DefaultButtonType: ButtonType {
+		CANCEL, CONFIRM, OK, CLOSE;
+
+		override val localizedName: String
+			get() = name.toLowerCase().capitalize() // todo: actually localize me
+	}
+
+	private lateinit var background: NinePatchView
+	private lateinit var hStack: StackView
+	private var iconView: TextureView? = null
+	private lateinit var vStack: StackView
+	private lateinit var messageLabel: Label
+	private var buttonContainer: View? = null
+	private var buttonStack: StackView? = null
+
+	override fun wasAdded() {
+		background = addSubview(NinePatchView(NinePatchTexture.PANEL_BG).apply { zIndex = -1.0 })
+
+		hStack = addSubview(StackView(Axis.HORIZONTAL, StackView.Distribution.LEADING, spacing = 8.0))
+
+		if (iconTexture != null) {
+			iconView = hStack.addArrangedSubview(TextureView(iconTexture))
+		}
+
+		vStack = hStack.addArrangedSubview(StackView(Axis.VERTICAL, spacing = 4.0))
+
+		vStack.addArrangedSubview(Label(title, shadow = false).apply {
+			textColor = Color(0x404040)
+		})
+		messageLabel = vStack.addArrangedSubview(Label(message, shadow = false).apply {
+			textColor = Color(0x404040)
+		})
+
+		if (buttonTypes.isNotEmpty()) {
+			buttonContainer = vStack.addArrangedSubview(View())
+			buttonStack = buttonContainer!!.addSubview(StackView(Axis.HORIZONTAL))
+			for (type in buttonTypes) {
+				buttonStack!!.addArrangedSubview(Button(Label(type.localizedName)).apply {
+					handler = {
+						this@DialogView.buttonCallback(type, this@DialogView.window!!)
+					}
+				})
+			}
+		}
+
+		super.wasAdded()
+	}
+
+	override fun createInternalConstraints() {
+		super.createInternalConstraints()
+
+		solver.dsl {
+			centerXAnchor equalTo window!!.centerXAnchor
+			centerYAnchor equalTo window!!.centerYAnchor
+
+			widthAnchor greaterThanOrEqualTo 175
+
+			background.leftAnchor equalTo leftAnchor - 8
+			background.rightAnchor equalTo rightAnchor + 8
+			background.topAnchor equalTo topAnchor - 8
+			background.bottomAnchor equalTo bottomAnchor + 8
+
+			hStack.leftAnchor equalTo leftAnchor
+			hStack.rightAnchor equalTo rightAnchor
+			hStack.topAnchor equalTo topAnchor
+			hStack.bottomAnchor equalTo bottomAnchor
+
+			if (iconView != null) {
+				hStack.bottomAnchor greaterThanOrEqualTo iconView!!.bottomAnchor
+			}
+			hStack.bottomAnchor greaterThanOrEqualTo vStack.bottomAnchor
+
+			if (iconView != null) {
+				iconView!!.widthAnchor equalTo 30
+				iconView!!.heightAnchor equalTo 30
+			}
+
+			messageLabel.heightAnchor greaterThanOrEqualTo 50
+
+			if (buttonContainer != null) {
+				buttonStack!!.heightAnchor equalTo buttonContainer!!.heightAnchor
+				buttonStack!!.centerYAnchor equalTo buttonContainer!!.centerYAnchor
+
+				buttonStack!!.rightAnchor equalTo buttonContainer!!.rightAnchor
+			}
+		}
+	}
+
+}

src/main/kotlin/net/shadowfacts/cacao/view/Label.kt

@@ -0,0 +1,123 @@
+package net.shadowfacts.cacao.view
+
+import net.minecraft.client.MinecraftClient
+import net.minecraft.client.font.TextRenderer
+import net.minecraft.client.util.math.MatrixStack
+import net.shadowfacts.cacao.geometry.Point
+import net.shadowfacts.cacao.geometry.Size
+import net.shadowfacts.cacao.util.Color
+import net.shadowfacts.cacao.util.RenderHelper
+
+/**
+ * A simple View that displays text. Allows for controlling the color and shadow of the text. Label cannot be used
+ * for multi-line text, instead use [TextView].
+ *
+ * @author shadowfacts
+ * @param text The text of this label.
+ * @param shadow Whether the text should be rendered with a shadow or not.
+ * @param maxLines The maximum number of lines of text to render.
+ * 					`0` means that there is no line limit and all lines will be rendered.
+ * 					When using a non-zero [maxLines] value, the [intrinsicContentSize] of the Label still assumes all
+ * 					content on one line. So, constraints must be provided to calculate the actual width to use for line
+ * 					wrapping.
+ */
+class Label(
+		text: String,
+		val shadow: Boolean = true,
+		val maxLines: Int = 0,
+		val wrappingMode: WrappingMode = WrappingMode.WRAP,
+		val textAlignment: TextAlignment = TextAlignment.LEFT
+): View() {
+
+	companion object {
+		private val textRenderer: TextRenderer
+			get() = MinecraftClient.getInstance().textRenderer
+	}
+
+	enum class WrappingMode {
+		WRAP, NO_WRAP
+	}
+
+	enum class TextAlignment {
+		LEFT, CENTER, RIGHT
+	}
+
+	/**
+	 * The text of this label. Mutating this field will update the intrinsic content size and trigger a layout.
+	 */
+	var text: String = text
+		set(value) {
+			field = value
+			updateIntrinsicContentSize()
+			// todo: setNeedsLayout instead of force unwrapping window
+			window!!.layout()
+		}
+	private lateinit var lines: List<String>
+
+	var textColor = Color.WHITE
+		set(value) {
+			field = value
+			textColorARGB = value.argb
+		}
+	private var textColorARGB: Int = textColor.argb
+
+	override fun wasAdded() {
+		super.wasAdded()
+
+		updateIntrinsicContentSize()
+	}
+
+	private fun updateIntrinsicContentSize() {
+		if (RenderHelper.disabled) return
+
+		val width = textRenderer.getWidth(text)
+		val height = textRenderer.fontHeight
+		intrinsicContentSize = Size(width.toDouble(), height.toDouble())
+	}
+
+	override fun drawContent(matrixStack: MatrixStack, mouse: Point, delta: Float) {
+		if (!this::lines.isInitialized) {
+			computeLines()
+		}
+
+		for (i in 0 until lines.size) {
+			val x = when (textAlignment) {
+				TextAlignment.LEFT -> 0.0
+				TextAlignment.CENTER -> (bounds.width + textRenderer.getWidth(lines[i])) / 2
+				TextAlignment.RIGHT -> bounds.width - textRenderer.getWidth(lines[i])
+			}
+			val y = i * textRenderer.fontHeight
+			if (shadow) {
+				textRenderer.drawWithShadow(matrixStack, lines[i], x.toFloat(), y.toFloat(), textColorARGB)
+			} else {
+				textRenderer.draw(matrixStack, lines[i], x.toFloat(), y.toFloat(), textColorARGB)
+			}
+		}
+	}
+
+	override fun didLayout() {
+		super.didLayout()
+
+		computeLines()
+	}
+
+	private fun computeLines() {
+		var lines = text.split("\n")
+		if (wrappingMode == WrappingMode.WRAP) {
+			lines = lines.flatMap {
+				wrapStringToWidthAsList(it, bounds.width)
+			}
+		}
+		if (0 < maxLines && maxLines < lines.size) {
+			lines = lines.dropLast(lines.size - maxLines)
+		}
+		this.lines = lines
+	}
+
+	private fun wrapStringToWidthAsList(string: String, width: Double): List<String> {
+		if (RenderHelper.disabled) return listOf(string)
+//		return textRenderer.wrapStringToWidthAsList(string, width.toInt())
+		TODO()
+	}
+
+}

src/main/kotlin/net/shadowfacts/cacao/view/NinePatchView.kt

@@ -0,0 +1,136 @@
+package net.shadowfacts.cacao.view
+
+import net.minecraft.client.util.math.MatrixStack
+import net.shadowfacts.cacao.geometry.Point
+import net.shadowfacts.cacao.geometry.Rect
+import net.shadowfacts.cacao.util.texture.NinePatchTexture
+import net.shadowfacts.cacao.util.RenderHelper
+import net.shadowfacts.cacao.util.properties.ResettableLazyProperty
+
+/**
+ * A helper class for drawing a [NinePatchTexture] in a view.
+ * `NinePatchView` will draw the given nine patch texture filling its bounds.
+ *
+ * This class and the region properties are left open for internal framework use, overriding them is not recommended.
+ *
+ * @author shadowfacts
+ * @param ninePatch The nine patch texture that this view will draw.
+ */
+open class NinePatchView(val ninePatch: NinePatchTexture): View() {
+
+	// Corners
+	private val topLeftDelegate = ResettableLazyProperty {
+		Rect(0.0, 0.0, ninePatch.cornerWidth.toDouble(), ninePatch.cornerHeight.toDouble())
+	}
+	protected open val topLeft by topLeftDelegate
+
+	private val topRightDelegate = ResettableLazyProperty {
+		Rect(bounds.width - ninePatch.cornerWidth, 0.0, ninePatch.cornerWidth.toDouble(), ninePatch.cornerHeight.toDouble())
+	}
+	protected open val topRight by topRightDelegate
+
+	private val bottomLeftDelegate = ResettableLazyProperty {
+		Rect(0.0, bounds.height - ninePatch.cornerHeight, ninePatch.cornerWidth.toDouble(), ninePatch.cornerHeight.toDouble())
+	}
+	protected open val bottomLeft by bottomLeftDelegate
+
+	private val bottomRightDelegate = ResettableLazyProperty {
+		Rect(bounds.width - ninePatch.cornerWidth, bounds.height - ninePatch.cornerHeight, ninePatch.cornerWidth.toDouble(), ninePatch.cornerHeight.toDouble())
+	}
+	protected open val bottomRight by bottomRightDelegate
+
+
+	// Edges
+	private val topMiddleDelegate = ResettableLazyProperty {
+		Rect(ninePatch.cornerWidth.toDouble(), topLeft.top, bounds.width - 2 * ninePatch.cornerWidth, ninePatch.cornerHeight.toDouble())
+	}
+	protected open val topMiddle by topMiddleDelegate
+
+	private val bottomMiddleDelegate = ResettableLazyProperty {
+		Rect(topMiddle.left, bottomLeft.top, topMiddle.width, topMiddle.height)
+	}
+	protected open val bottomMiddle by bottomMiddleDelegate
+
+	private val leftMiddleDelegate = ResettableLazyProperty {
+		Rect(topLeft.left, ninePatch.cornerHeight.toDouble(), ninePatch.cornerWidth.toDouble(), bounds.height - 2 * ninePatch.cornerHeight)
+	}
+	protected open val leftMiddle by leftMiddleDelegate
+
+	private val rightMiddleDelegate = ResettableLazyProperty {
+		Rect(topRight.left, leftMiddle.top, leftMiddle.width, leftMiddle.height)
+	}
+	protected open val rightMiddle by rightMiddleDelegate
+
+
+	// Center
+	private val centerDelegate = ResettableLazyProperty {
+		Rect(topLeft.right, topLeft.bottom, topMiddle.width, leftMiddle.height)
+	}
+	protected open val center by centerDelegate
+
+	private val delegates = listOf(topLeftDelegate, topRightDelegate, bottomLeftDelegate, bottomRightDelegate, topMiddleDelegate, bottomMiddleDelegate, leftMiddleDelegate, rightMiddleDelegate, centerDelegate)
+
+	override fun didLayout() {
+		super.didLayout()
+
+		delegates.forEach(ResettableLazyProperty<Rect>::reset)
+	}
+
+	override fun drawContent(matrixStack: MatrixStack, mouse: Point, delta: Float) {
+		drawCorners()
+		drawEdges()
+		drawCenter()
+	}
+
+	private fun drawCorners() {
+		RenderHelper.draw(topLeft, ninePatch.topLeft)
+		RenderHelper.draw(topRight, ninePatch.topRight)
+		RenderHelper.draw(bottomLeft, ninePatch.bottomLeft)
+		RenderHelper.draw(bottomRight, ninePatch.bottomRight)
+	}
+
+	private fun drawEdges() {
+		// Horizontal
+		for (i in 0 until (topMiddle.width.toInt() / ninePatch.centerWidth)) {
+			RenderHelper.draw(topMiddle.left + i * ninePatch.centerWidth, topMiddle.top, ninePatch.topMiddle.u, ninePatch.topMiddle.v, ninePatch.centerWidth.toDouble(), topMiddle.height, ninePatch.texture.width, ninePatch.texture.height)
+			RenderHelper.draw(bottomMiddle.left + i * ninePatch.centerWidth, bottomMiddle.top, ninePatch.bottomMiddle.u, ninePatch.bottomMiddle.v, ninePatch.centerWidth.toDouble(), bottomMiddle.height, ninePatch.texture.width, ninePatch.texture.height)
+		}
+		val remWidth = topMiddle.width.toInt() % ninePatch.centerWidth
+		if (remWidth > 0) {
+			RenderHelper.draw(topMiddle.right - remWidth, topMiddle.top, ninePatch.topMiddle.u, ninePatch.topMiddle.v, remWidth.toDouble(), ninePatch.cornerHeight.toDouble(), ninePatch.texture.width, ninePatch.texture.height)
+			RenderHelper.draw(bottomMiddle.right - remWidth, bottomMiddle.top, ninePatch.bottomMiddle.u, ninePatch.bottomMiddle.v, remWidth.toDouble(), ninePatch.cornerHeight.toDouble(), ninePatch.texture.width, ninePatch.texture.height)
+		}
+
+		// Vertical
+		for (i in 0 until (leftMiddle.height.toInt() / ninePatch.centerHeight)) {
+			RenderHelper.draw(leftMiddle.left, leftMiddle.top + i * ninePatch.centerHeight, ninePatch.leftMiddle.u, ninePatch.leftMiddle.v, ninePatch.cornerWidth.toDouble(), ninePatch.centerHeight.toDouble(), ninePatch.texture.width, ninePatch.texture.height)
+			RenderHelper.draw(rightMiddle.left, rightMiddle.top + i * ninePatch.centerHeight, ninePatch.rightMiddle.u, ninePatch.rightMiddle.v, ninePatch.cornerWidth.toDouble(), ninePatch.centerHeight.toDouble(), ninePatch.texture.width, ninePatch.texture.height)
+		}
+		val remHeight = leftMiddle.height.toInt() % ninePatch.centerHeight
+		if (remHeight > 0) {
+			RenderHelper.draw(leftMiddle.left, leftMiddle.bottom - remHeight, ninePatch.leftMiddle.u, ninePatch.leftMiddle.v, ninePatch.cornerWidth.toDouble(), remHeight.toDouble(), ninePatch.texture.width, ninePatch.texture.height)
+			RenderHelper.draw(rightMiddle.left, rightMiddle.bottom - remHeight, ninePatch.rightMiddle.u, ninePatch.rightMiddle.v, ninePatch.cornerWidth.toDouble(), remHeight.toDouble(), ninePatch.texture.width, ninePatch.texture.height)
+		}
+	}
+
+	private fun drawCenter() {
+		for (i in 0 until (center.height.toInt() / ninePatch.centerHeight)) {
+			drawCenterRow(center.top + i * ninePatch.centerHeight.toDouble(), ninePatch.centerHeight.toDouble())
+		}
+		val remHeight = center.height.toInt() % ninePatch.centerHeight
+		if (remHeight > 0) {
+			drawCenterRow(center.bottom - remHeight, remHeight.toDouble())
+		}
+	}
+
+	private fun drawCenterRow(y: Double, height: Double) {
+		for (i in 0 until (center.width.toInt() / ninePatch.centerWidth)) {
+			RenderHelper.draw(center.left + i * ninePatch.centerWidth, y, ninePatch.center.u, ninePatch.center.v, ninePatch.centerWidth.toDouble(), height, ninePatch.texture.width, ninePatch.texture.height)
+		}
+		val remWidth = center.width.toInt() % ninePatch.centerWidth
+		if (remWidth > 0) {
+			RenderHelper.draw(center.right - remWidth, y, ninePatch.center.u, ninePatch.center.v, remWidth.toDouble(), height, ninePatch.texture.width, ninePatch.texture.height)
+		}
+	}
+
+}

src/main/kotlin/net/shadowfacts/cacao/view/StackView.kt

@@ -0,0 +1,212 @@
+package net.shadowfacts.cacao.view
+
+import net.shadowfacts.kiwidsl.dsl
+import net.shadowfacts.cacao.LayoutVariable
+import net.shadowfacts.cacao.geometry.Axis
+import net.shadowfacts.cacao.geometry.AxisPosition
+import net.shadowfacts.cacao.geometry.AxisPosition.*
+import no.birkett.kiwi.Constraint
+import java.util.*
+
+/**
+ * A view that lays out its children in a stack along either the horizontal for vertical axes.
+ * This view does not have any content of its own.
+ *
+ * Only arranged subviews will be laid out in the stack mode, normal subviews must perform their own layout.
+ *
+ * @author shadowfacts
+ * @param axis The primary axis that this stack lays out its children along.
+ * @param distribution The mode by which this stack lays out its children along the axis perpendicular to the
+ * 						primary [axis].
+ */
+open class StackView(
+		val axis: Axis,
+		val distribution: Distribution = Distribution.FILL,
+		val spacing: Double = 0.0
+): View() {
+
+	// the internal mutable, list of arranged subviews
+	private val _arrangedSubviews = LinkedList<View>()
+	/**
+	 * The list of arranged subviews belonging to this stack view.
+	 * This list should never be mutated directly, only be calling the [addArrangedSubview]/[removeArrangedSubview]
+	 * methods.
+	 */
+	val arrangedSubviews: List<View> = _arrangedSubviews
+
+	private var leadingConnection: Constraint? = null
+	private var trailingConnection: Constraint? = null
+	private var arrangedSubviewConnections = mutableListOf<Constraint>()
+
+	/**
+	 * Adds an arranged subview to this view.
+	 * Arranged subviews are laid out according to the stack. If you wish to add a subview that is laid out separately,
+	 * use the normal [addSubview] method.
+	 *
+	 * @param view The view to add.
+	 * @param index The index in this stack to add the view at.
+	 * 				By default, adds the view to the end of the stack.
+	 * @return The view that was added, as a convenience.
+	 */
+	fun <T: View> addArrangedSubview(view: T, index: Int = arrangedSubviews.size): T {
+		addSubview(view)
+		_arrangedSubviews.add(index, view)
+
+		addConstraintsForArrangedView(view, index)
+
+		return view
+	}
+
+	private fun addConstraintsForArrangedView(view: View, index: Int) {
+		if (index == 0) {
+			if (leadingConnection != null) {
+				solver.removeConstraint(leadingConnection)
+			}
+			solver.dsl {
+				leadingConnection = anchor(LEADING) equalTo anchor(LEADING, view)
+			}
+		}
+		if (index == arrangedSubviews.size - 1) {
+			if (trailingConnection != null) {
+				solver.removeConstraint(trailingConnection)
+			}
+			solver.dsl {
+				trailingConnection = anchor(TRAILING, view) equalTo anchor(TRAILING)
+			}
+		}
+		if (arrangedSubviews.size > 1) {
+			solver.dsl {
+				val previous = arrangedSubviews.getOrNull(index - 1)
+				val next = arrangedSubviews.getOrNull(index + 1)
+				if (next != null) {
+					arrangedSubviewConnections.add(index, anchor(TRAILING, view) equalTo (anchor(LEADING, next) + spacing))
+				}
+				if (previous != null) {
+					arrangedSubviewConnections.add(index - 1, anchor(TRAILING, previous) equalTo (anchor(LEADING, view) - spacing))
+				}
+			}
+		}
+		solver.dsl {
+			when (distribution) {
+				Distribution.LEADING ->
+					perpAnchor(LEADING) equalTo perpAnchor(LEADING, view)
+				Distribution.TRAILING ->
+					perpAnchor(TRAILING) equalTo perpAnchor(TRAILING, view)
+				Distribution.FILL -> {
+					perpAnchor(LEADING) equalTo perpAnchor(LEADING, view)
+					perpAnchor(TRAILING) equalTo perpAnchor(TRAILING, view)
+				}
+				Distribution.CENTER ->
+					perpAnchor(CENTER) equalTo perpAnchor(CENTER, view)
+			}
+		}
+	}
+
+	private fun anchor(position: AxisPosition, view: View = this): LayoutVariable {
+		return view.getAnchor(axis, position)
+	}
+	private fun perpAnchor(position: AxisPosition, view: View = this): LayoutVariable {
+		return view.getAnchor(axis.perpendicular, position)
+	}
+
+	/**
+	 * Defines the modes of how content is distributed in a stack view along the perpendicular axis (i.e. the
+	 * non-primary axis).
+	 *
+	 * ASCII-art examples are shown below in a stack view with the primary axis [Axis.VERTICAL].
+	 */
+	enum class Distribution {
+		/**
+		 * The leading edges of arranged subviews are pinned to the leading edge of the stack view.
+		 * ```
+		 * ┌─────────────────────────────┐
+		 * │┌─────────────┐              │
+		 * ││             │              │
+		 * ││             │              │
+		 * ││             │              │
+		 * │└─────────────┘              │
+		 * │┌─────────┐                  │
+		 * ││         │                  │
+		 * ││         │                  │
+		 * ││         │                  │
+		 * │└─────────┘                  │
+		 * │┌───────────────────────────┐│
+		 * ││                           ││
+		 * ││                           ││
+		 * ││                           ││
+		 * │└───────────────────────────┘│
+		 * └─────────────────────────────┘
+		 * ```
+		 */
+		LEADING,
+		/**
+		 * The centers of the arranged subviews are pinned to the center of the stack view.
+		 * ```
+		 * ┌─────────────────────────────┐
+		 * │       ┌─────────────┐       │
+		 * │       │             │       │
+		 * │       │             │       │
+		 * │       │             │       │
+		 * │       └─────────────┘       │
+		 * │         ┌─────────┐         │
+		 * │         │         │         │
+		 * │         │         │         │
+		 * │         │         │         │
+		 * │         └─────────┘         │
+		 * │┌───────────────────────────┐│
+		 * ││                           ││
+		 * ││                           ││
+		 * ││                           ││
+		 * │└───────────────────────────┘│
+		 * └─────────────────────────────┘
+		 * ```
+		 */
+		CENTER,
+		/**
+		 * The trailing edges of arranged subviews are pinned to the leading edge of the stack view.
+		 * ```
+		 * ┌─────────────────────────────┐
+		 * │              ┌─────────────┐│
+		 * │              │             ││
+		 * │              │             ││
+		 * │              │             ││
+		 * │              └─────────────┘│
+		 * │                  ┌─────────┐│
+		 * │                  │         ││
+		 * │                  │         ││
+		 * │                  │         ││
+		 * │                  └─────────┘│
+		 * │┌───────────────────────────┐│
+		 * ││                           ││
+		 * ││                           ││
+		 * ││                           ││
+		 * │└───────────────────────────┘│
+		 * └─────────────────────────────┘
+		 * ```
+		 */
+		TRAILING,
+		/**
+		 * The arranged subviews fill the perpendicular axis of the stack view.
+		 * ```
+		 * ┌─────────────────────────────┐
+		 * │┌───────────────────────────┐│
+		 * ││                           ││
+		 * ││                           ││
+		 * ││                           ││
+		 * │└───────────────────────────┘│
+		 * │┌───────────────────────────┐│
+		 * ││                           ││
+		 * ││                           ││
+		 * ││                           ││
+		 * │└───────────────────────────┘│
+		 * │┌───────────────────────────┐│
+		 * ││                           ││
+		 * ││                           ││
+		 * ││                           ││
+		 * │└───────────────────────────┘│
+		 * └─────────────────────────────┘
+		 * ```
+		 */
+		FILL
+	}
+}

src/main/kotlin/net/shadowfacts/cacao/view/TextureView.kt

@@ -0,0 +1,20 @@
+package net.shadowfacts.cacao.view
+
+import net.minecraft.client.util.math.MatrixStack
+import net.shadowfacts.cacao.geometry.Point
+import net.shadowfacts.cacao.util.RenderHelper
+import net.shadowfacts.cacao.util.texture.Texture
+
+/**
+ * A helper class for drawing a [Texture] in a view.
+ * `TextureView` will draw the given texture filling the bounds of the view.
+ *
+ * @author shadowfacts
+ */
+class TextureView(var texture: Texture): View() {
+
+	override fun drawContent(matrixStack: MatrixStack, mouse: Point, delta: Float) {
+		RenderHelper.draw(bounds, texture)
+	}
+
+}

src/main/kotlin/net/shadowfacts/cacao/view/View.kt

@@ -0,0 +1,391 @@
+package net.shadowfacts.cacao.view
+
+import net.minecraft.client.util.math.MatrixStack
+import net.shadowfacts.kiwidsl.dsl
+import net.shadowfacts.cacao.LayoutVariable
+import net.shadowfacts.cacao.Window
+import net.shadowfacts.cacao.geometry.*
+import net.shadowfacts.cacao.util.*
+import net.shadowfacts.cacao.util.properties.ObservableLateInitProperty
+import no.birkett.kiwi.Constraint
+import no.birkett.kiwi.Solver
+import java.lang.RuntimeException
+import java.util.*
+
+/**
+ * The base Cacao View class. Provides layout anchors, properties, and helper methods.
+ * Doesn't draw anything itself (unless [backgroundColor] is specified), but may be used for encapsulation/grouping.
+ *
+ * @author shadowfacts
+ */
+open class View() {
+
+	/**
+	* The window whose view hierarchy this view belongs to.
+	* Not initialized until the root view in this hierarchy has been added to a hierarchy,
+	* using it before that will throw a runtime exception.
+	*/
+	var window: Window? = null
+
+	/**
+	 * The constraint solver used by the [net.shadowfacts.cacao.Window] this view belongs to.
+	 * Not initialized until [wasAdded] called, using it before that will throw a runtime exception.
+	 */
+	lateinit var solver: Solver
+
+	/**
+	 * Layout anchor for the left edge of this view in the window's coordinate system.
+	 */
+	val leftAnchor = LayoutVariable(this, "left")
+	/**
+	 * Layout anchor for the right edge of this view in the window's coordinate system.
+	 */
+	val rightAnchor = LayoutVariable(this, "right")
+	/**
+	 * Layout anchor for the top edge of this view in the window's coordinate system.
+	 */
+	val topAnchor = LayoutVariable(this, "top")
+	/**
+	 * Layout anchor for the bottom edge of this view in the window's coordinate system.
+	 */
+	val bottomAnchor = LayoutVariable(this, "bottom")
+	/**
+	 * Layout anchor for the width of this view in the window's coordinate system.
+	 */
+	val widthAnchor = LayoutVariable(this, "width")
+	/**
+	 * Layout anchor for the height of this view in the window's coordinate system.
+	 */
+	val heightAnchor = LayoutVariable(this, "height")
+	/**
+	 * Layout anchor for the center X position of this view in the window's coordinate system.
+	 */
+	val centerXAnchor = LayoutVariable(this, "centerX")
+	/**
+	 * Layout anchor for the center Y position of this view in the window's coordinate system.
+	 */
+	val centerYAnchor = LayoutVariable(this, "centerY")
+
+	/**
+	 * Whether this view uses constraint-based layout.
+	 * If `false`, the view's `frame` must be set manually and the layout anchors may not be used.
+	 * Note: some views (such as [StackView] require arranged subviews to use constraint based layout.
+	 *
+	 * Default is `true`.
+	 */
+	var usesConstraintBasedLayout = true
+
+	/**
+	 * The rectangle for this view in the coordinate system of its superview view (or the window, if there is no superview).
+	 * If using constraint based layout, this property is not initialized until [didLayout] called.
+	 * Otherwise, this must be set manually.
+	 * Setting this property updates the [bounds].
+	 */
+	var frame: Rect by ObservableLateInitProperty { this.bounds = Rect(Point.ORIGIN, it.size) }
+	/**
+	 * The rectangle for this view in its own coordinate system.
+	 * If using constraint based layout, this property is not initialized until [didLayout] called.
+	 * Otherwise, this will be initialized when [frame] is set.
+	 */
+	lateinit var bounds: Rect
+
+	/**
+	 * The position on the Z-axis of this view.
+	 * Views are rendered from lowest Z index to highest. Clicks are handled from highest to lowest.
+	 */
+	var zIndex: Double = 0.0
+
+	/**
+	 * The intrinsic size of this view's content. May be null if the view doesn't have any content or there is no
+	 * intrinsic size.
+	 *
+	 * Setting this creates/updates [no.birkett.kiwi.Strength.WEAK] constraints on this view's width/height using
+	 * the size.
+	 */
+	var intrinsicContentSize: Size? = null
+		set(value) {
+			updateIntrinsicContentSizeConstraints(intrinsicContentSize, value)
+			field = value
+		}
+	private var intrinsicContentSizeWidthConstraint: Constraint? = null
+	private var intrinsicContentSizeHeightConstraint: Constraint? = null
+
+	/**
+	 * The background color of this view.
+	 */
+	var backgroundColor = Color.CLEAR
+
+	var respondsToDragging = false
+
+	/**
+	 * This view's parent view. If `null`, this view is a top-level view in the [Window].
+	 */
+	var superview: View? = null
+	// _subviews is the internal, mutable object since we only want it to be mutated by the add/removeSubview methods
+	private val _subviews = LinkedList<View>()
+	private var subviewsSortedByZIndex: List<View> = listOf()
+
+	/**
+	 * The list of all the subviews of this view.
+	 * This list should never by mutated directly, only by the [addSubview]/[removeSubview] methods.
+	 */
+	val subviews: List<View> = _subviews
+
+	constructor(frame: Rect): this() {
+		this.usesConstraintBasedLayout = false
+		this.frame = frame
+	}
+
+	/**
+	 * Helper method for retrieve the anchor for a specific position on the given axis.
+	 */
+	fun getAnchor(axis: Axis, position: AxisPosition): LayoutVariable {
+		return when (axis) {
+			Axis.HORIZONTAL ->
+				when (position) {
+					AxisPosition.LEADING -> leftAnchor
+					AxisPosition.CENTER -> centerXAnchor
+					AxisPosition.TRAILING -> rightAnchor
+				}
+			Axis.VERTICAL ->
+				when (position) {
+					AxisPosition.LEADING -> topAnchor
+					AxisPosition.CENTER -> centerYAnchor
+					AxisPosition.TRAILING -> bottomAnchor
+				}
+		}
+	}
+
+	/**
+	 * Adds the given subview as a child of this view.
+	 *
+	 * @param view The view to add.
+	 * @return The view that was added, as a convenience.
+	 */
+	fun <T: View> addSubview(view: T): T {
+		_subviews.add(view)
+		subviewsSortedByZIndex = subviews.sortedBy(View::zIndex)
+
+		view.superview = this
+		view.solver = solver
+		view.window = window
+
+		view.wasAdded()
+
+		return view
+	}
+
+	/**
+	 * Removes the given view from this view's children and removes all constraints associated with it.
+	 *
+	 * @param view The view to removed as a child of this view.
+	 * @throws RuntimeException If the given [view] is not a subview of this view.
+	 */
+	fun removeSubview(view: View) {
+		if (view.superview != this) {
+			throw RuntimeException("Cannot remove subview whose superview is not this view")
+		}
+		solver.constraints.filter { constraint ->
+			constraint.getVariables().any { it is LayoutVariable && it.owner == view }
+		}.forEach(solver::removeConstraint)
+		_subviews.remove(view)
+		subviewsSortedByZIndex = subviews.sortedBy(View::zIndex)
+
+		view.superview = null
+		// todo: does this need to be reset
+//		view.solver = null
+		view.window = null
+
+		// todo: is this necessary?
+//		view.wasRemoved()
+	}
+
+	/**
+	 * Removes this view from its superview, if it has one.
+	 */
+	fun removeFromSuperview() {
+		superview?.removeSubview(this)
+	}
+
+	/**
+	 * Finds all subviews that contain the given point.
+	 *
+	 * @param point The point to find subviews for, in the coordinate system of this view.
+	 * @return All views that contain the given point.
+	 */
+	fun subviewsAtPoint(point: Point): List<View> {
+		return subviews.filter { point in it.frame }
+	}
+
+	/**
+	 * Attempts to find a subview which contains the given point.
+	 * If multiple subviews contain the given point, which one this method returns is undefined.
+	 * [subviewsAtPoint] may be used, and the resulting List sorted by [View.zIndex].
+	 *
+	 * @param point The point to find a subview for, in the coordinate system of this view.
+	 * @return The view, if any, that contains the given point.
+	 */
+	fun subviewAtPoint(point: Point): View? {
+		return subviews.firstOrNull { point in it.frame }
+	}
+
+	/**
+	 * Called when this view was added to a view hierarchy.
+	 * If overridden, the super-class method must be called.
+	 */
+	open fun wasAdded() {
+		createInternalConstraints()
+		updateIntrinsicContentSizeConstraints(null, intrinsicContentSize)
+	}
+
+	/**
+	 * Called during [wasAdded] to add any constraints to the [solver] that are internal to this view.
+	 * If overridden, the super-class method must be called.
+	 */
+	protected open fun createInternalConstraints() {
+		if (!usesConstraintBasedLayout) return
+
+		solver.dsl {
+			rightAnchor equalTo (leftAnchor + widthAnchor)
+			bottomAnchor equalTo (topAnchor + heightAnchor)
+			centerXAnchor equalTo (leftAnchor + widthAnchor / 2)
+			centerYAnchor equalTo (topAnchor + heightAnchor / 2)
+		}
+	}
+
+	private fun updateIntrinsicContentSizeConstraints(old: Size?, new: Size?) {
+		if (!usesConstraintBasedLayout || !this::solver.isInitialized) return
+
+		if (old != null) {
+			solver.removeConstraint(intrinsicContentSizeWidthConstraint!!)
+			solver.removeConstraint(intrinsicContentSizeHeightConstraint!!)
+		}
+		if (new != null) {
+			solver.dsl {
+				this@View.intrinsicContentSizeWidthConstraint = (widthAnchor.equalTo(new.width, strength = WEAK))
+				this@View.intrinsicContentSizeHeightConstraint = (heightAnchor.equalTo(new.height, strength = WEAK))
+			}
+		}
+	}
+
+	/**
+	 * Called after this view has been laid-out.
+	 * If overridden, the super-class method must be called.
+	 */
+	open fun didLayout() {
+		subviews.forEach(View::didLayout)
+
+		if (usesConstraintBasedLayout) {
+			val superviewLeft = superview?.leftAnchor?.value ?: 0.0
+			val superviewTop = superview?.topAnchor?.value ?: 0.0
+			frame = Rect(leftAnchor.value - superviewLeft, topAnchor.value - superviewTop, widthAnchor.value, heightAnchor.value)
+			bounds = Rect(0.0, 0.0, widthAnchor.value, heightAnchor.value)
+		}
+	}
+
+	/**
+	 * Called to draw this view.
+	 * This method should not be called directly, it is called by the parent view/window.
+	 * This method generally should not be overridden, but it is left open for internal framework use.
+	 * Use [drawContent] to draw any custom content.
+	 *
+	 * @param mouse The position of the mouse in the coordinate system of this view.
+	 * @param delta The time since the last frame.
+	 */
+	open fun draw(matrixStack: MatrixStack, mouse: Point, delta: Float) {
+		RenderHelper.pushMatrix()
+		RenderHelper.translate(frame.left, frame.top)
+
+		RenderHelper.fill(matrixStack, bounds, backgroundColor)
+
+		drawContent(matrixStack, mouse, delta)
+
+		subviewsSortedByZIndex.forEach {
+			val mouseInView = convert(mouse, to = it)
+			it.draw(matrixStack, mouseInView, delta)
+		}
+
+		RenderHelper.popMatrix()
+	}
+
+	/**
+	 * Called during [draw] to draw content that's part of this view.
+	 * During this method, the OpenGL coordinate system has been translated so the origin is at the top left corner
+	 * of this view. Be careful not to translate additionally, and not to draw outside the [bounds] of the view.
+	 *
+	 * @param mouse The position of the mouse in the coordinate system of this view.
+	 * @param delta The time since the last frame.
+	 */
+	open fun drawContent(matrixStack: MatrixStack, mouse: Point, delta: Float) {}
+
+	/**
+	 * Called when this view is clicked. May delegate to [subviews].
+	 * If overridden, the super-class method does not have to be called. Intentionally not calling it may be used
+	 * to prevent [subviews] from receiving click events.
+	 *
+	 * @param point The point in the coordinate system of this view that the mouse was clicked.
+	 * @param mouseButton The mouse button used to click.
+	 * @return Whether the mouse click was handled by this view or any subviews.
+	 */
+	open fun mouseClicked(point: Point, mouseButton: MouseButton): Boolean {
+		val view = subviewsAtPoint(point).maxBy(View::zIndex)
+		if (view != null) {
+			val pointInView = convert(point, to = view)
+			return view.mouseClicked(pointInView, mouseButton)
+		}
+		return false
+	}
+
+	open fun mouseDragged(startPoint: Point, delta: Point, mouseButton: MouseButton): Boolean {
+		val view = subviewsAtPoint(startPoint).maxBy(View::zIndex)
+		if (view != null) {
+			val startInView = convert(startPoint, to = view)
+			return view.mouseDragged(startInView, delta, mouseButton)
+		}
+		return false
+	}
+
+	/**
+	 * Converts the given point in this view's coordinate system to the coordinate system of another view or the window.
+	 *
+	 * @param point The point to convert, in the coordinate system of this view.
+	 * @param to The view to convert to. If `null`, it will be converted to the window's coordinate system.
+	 * @return The point in the coordinate system of the [to] view.
+	 */
+	fun convert(point: Point, to: View?): Point {
+		if (to != null) {
+			val ancestor = LowestCommonAncestor.find(this, to, View::superview)
+			@Suppress("NAME_SHADOWING") var point = point
+
+			// Convert up to the LCA
+			var view: View? = this
+			while (view != null && view != ancestor) {
+				point = Point(point.x + view.frame.left, point.y + view.frame.top)
+				view = view.superview
+			}
+
+			// Convert back down to the other view
+			view = to
+			while (view != null && view != ancestor) {
+				point = Point(point.x - view.frame.left, point.y - view.frame.top)
+				view = view.superview
+			}
+
+			return point
+		} else {
+			return Point(leftAnchor.value + point.x, topAnchor.value + point.y)
+		}
+	}
+
+	/**
+	 * Converts the given rectangle in this view's coordinate system to the coordinate system of another view or the window.
+	 *
+	 * @param rect The rectangle to convert, in the coordinate system of this view.
+	 * @param to The view to convert to. If `null`, it will be converted to the window's coordinate system.
+	 * @return The rectangle in the coordinate system of the [to] view.
+	 */
+	fun convert(rect: Rect, to: View?): Rect {
+		return Rect(convert(rect.origin, to), rect.size)
+	}
+
+}

src/main/kotlin/net/shadowfacts/cacao/view/button/AbstractButton.kt

@@ -0,0 +1,117 @@
+package net.shadowfacts.cacao.view.button
+
+import net.minecraft.client.util.math.MatrixStack
+import net.shadowfacts.cacao.geometry.Point
+import net.shadowfacts.cacao.util.MouseButton
+import net.shadowfacts.cacao.util.texture.NinePatchTexture
+import net.shadowfacts.cacao.util.RenderHelper
+import net.shadowfacts.cacao.view.NinePatchView
+import net.shadowfacts.cacao.view.View
+import net.shadowfacts.kiwidsl.dsl
+
+/**
+ * A abstract button class. Cannot be constructed directly, used for creating button implementations with their own logic.
+ * Use [Button] for a generic no-frills button.
+ *
+ * @author shadowfacts
+ * @param Impl The type of the concrete implementation of the button.
+ * 				Used to allow the [handler] to receive the exact button type that was constructed.
+ * @param content The [View] that provides the content of this button.
+ * 					Will be added as a subview of the button and laid out using constraints.
+ * @param padding The padding between the [content] and the edges of the button.
+ */
+abstract class AbstractButton<Impl: AbstractButton<Impl>>(val content: View, val padding: Double = 4.0): View() {
+
+	/**
+	 * The function that handles when this button is clicked.
+	 * The parameter is the type of the concrete button implementation that was used.
+	 */
+	var handler: ((Impl) -> Unit)? = null
+
+	/**
+	 * Whether the button is disabled.
+	 * Disabled buttons have a different background ([disabledBackground]) and do not receive click events.
+	 */
+	var disabled = false
+
+	/**
+	 * The normal background view to draw behind the button content. It will be added as a subview during [wasAdded],
+	 * so all background view properties must be specified prior to the button being added to a view hierarchy.
+	 *
+	 * The background will fill the entire button (going beneath the content [padding]).
+	 * There are also [hoveredBackground] and [disabledBackground] for those states.
+	 * If a [backgroundColor] is specified, it will be drawn behind the background View and thus not visible
+	 * unless the background view is not fully opaque.
+	 */
+	var background: View? = NinePatchView(NinePatchTexture.BUTTON_BG)
+	/**
+	 * The background to draw when the button is hovered over by the mouse.
+	 * If `null`, the normal [background] will be used.
+	 * @see background
+	 */
+	var hoveredBackground: View? = NinePatchView(NinePatchTexture.BUTTON_HOVERED_BG)
+	/**
+	 * The background to draw when the button is [disabled].
+	 * If `null`, the normal [background] will be used.
+	 * @see background
+	 */
+	var disabledBackground: View? = NinePatchView(NinePatchTexture.BUTTON_DISABLED_BG)
+
+	override fun wasAdded() {
+		solver.dsl {
+			addSubview(content)
+			content.leftAnchor equalTo (leftAnchor + padding)
+			content.rightAnchor equalTo (rightAnchor - padding)
+			content.topAnchor equalTo (topAnchor + padding)
+			content.bottomAnchor equalTo (bottomAnchor - padding)
+
+			listOfNotNull(background, hoveredBackground, disabledBackground).forEach {
+				addSubview(it)
+				it.leftAnchor equalTo leftAnchor
+				it.rightAnchor equalTo rightAnchor
+				it.topAnchor equalTo topAnchor
+				it.bottomAnchor equalTo bottomAnchor
+			}
+		}
+
+		super.wasAdded()
+	}
+
+	override fun draw(matrixStack: MatrixStack, mouse: Point, delta: Float) {
+		RenderHelper.pushMatrix()
+		RenderHelper.translate(frame.left, frame.top)
+
+		RenderHelper.fill(matrixStack, bounds, backgroundColor)
+
+		var currentBackground: View? = background
+		if (mouse in bounds) {
+			currentBackground = hoveredBackground ?: currentBackground
+		}
+		if (disabled) {
+			currentBackground = disabledBackground ?: currentBackground
+		}
+		// don't need to convert mouse to background coordinate system
+		// the edges are all pinned, so the coordinate space is the same
+		currentBackground?.draw(matrixStack, mouse, delta)
+
+		val mouseInContent = convert(mouse, to = content)
+		content.draw(matrixStack, mouseInContent, delta)
+
+		// don't draw subviews, otherwise all background views + content will get drawn
+
+		RenderHelper.popMatrix()
+	}
+
+	override fun mouseClicked(point: Point, mouseButton: MouseButton): Boolean {
+		if (disabled) return false
+
+		// We can perform an unchecked cast here because we are certain that Impl will be the concrete implementation
+		// of AbstractButton.
+		// For example, an implementing class may be defined as such: `class Button: AbstractButton<Button>`
+		@Suppress("UNCHECKED_CAST")
+		handler?.invoke(this as Impl)
+
+		return true
+	}
+
+}

src/main/kotlin/net/shadowfacts/cacao/view/button/Button.kt

@@ -0,0 +1,12 @@
+package net.shadowfacts.cacao.view.button
+
+import net.shadowfacts.cacao.view.View
+
+/**
+ * A simple button implementation that provides no additional logic.
+ *
+ * @author shadowfacts
+ * @param content The [View] that provides the content of this button.
+ * @param padding The padding between the [content] and the edges of the button.
+ */
+class Button(content: View, padding: Double = 4.0): AbstractButton<Button>(content, padding)

src/main/kotlin/net/shadowfacts/cacao/view/button/DropdownButton.kt

@@ -0,0 +1,206 @@
+package net.shadowfacts.cacao.view.button
+
+import net.minecraft.util.Identifier
+import net.shadowfacts.cacao.Window
+import net.shadowfacts.cacao.geometry.Axis
+import net.shadowfacts.cacao.geometry.Point
+import net.shadowfacts.cacao.geometry.Rect
+import net.shadowfacts.cacao.util.MouseButton
+import net.shadowfacts.cacao.util.texture.NinePatchTexture
+import net.shadowfacts.cacao.util.texture.Texture
+import net.shadowfacts.cacao.util.properties.ResettableLazyProperty
+import net.shadowfacts.cacao.view.NinePatchView
+import net.shadowfacts.cacao.view.StackView
+import net.shadowfacts.cacao.view.TextureView
+import net.shadowfacts.cacao.view.View
+import net.shadowfacts.kiwidsl.dsl
+
+/**
+ * A button that provides a dropdown for the user to select from a list of values.
+ * The button itself shows a [ContentView] representing the currently selected [Value] and an image indicator that serves
+ * as a hint for the ability to click the button and display the dropdown.
+ *
+ * The dropdown list itself is displayed by presenting a new [Window] at the front of the window stack.
+ * Each possible value is represented in the list by a button containing a [ContentView] for that value, with the button
+ * for the current value being disabled.
+ *
+ * @author shadowfacts
+ * @param Value The type of value that the dropdown selects.
+ * @param ContentView The specific type of the [View] that represents selected item in the button and each item in the dropdown list.
+ * @param initialValue The initial value of the dropdown button.
+ * @param allValues List of all allowed values for the dropdown.
+ * @param createView A function that creates a [ContentView] representing the given [Value].
+ * 						Positioning of content views is handled by the dropdown.
+ * @param updateView A function for updating the view used as the button's 'label' that's visible even when the dropdown isn't.
+ */
+class DropdownButton<Value, ContentView: View>(
+		val initialValue: Value,
+		val allValues: Iterable<Value>,
+		val createView: (Value) -> ContentView,
+		val updateView: (newValue: Value, view: ContentView) -> Unit,
+		padding: Double = 4.0
+): AbstractButton<DropdownButton<Value, ContentView>>(
+		StackView(Axis.HORIZONTAL),
+		padding
+) {
+
+	companion object {
+		val DROPDOWN_INDICATOR = Texture(Identifier("asmr", "textures/gui/dropdown.png"), 0, 0)
+	}
+
+	private val stackView: StackView
+		get() = content as StackView
+
+	private val contentView: ContentView
+		get() = stackView.arrangedSubviews.first() as ContentView
+
+	private lateinit var dropdownIndicator: TextureView
+
+	/**
+	 * The currently selected [Value] of the dropdown.
+	 */
+	var value: Value = initialValue
+		set(value) {
+			field = value
+			updateView(value, contentView)
+			// todo: setNeedsLayout instead of force unwrapping window
+			window!!.layout()
+		}
+
+	override fun wasAdded() {
+		super.wasAdded()
+
+		stackView.addArrangedSubview(createView(initialValue))
+		dropdownIndicator = stackView.addArrangedSubview(TextureView(DROPDOWN_INDICATOR))
+
+		solver.dsl {
+			dropdownIndicator.widthAnchor equalTo 9
+			dropdownIndicator.heightAnchor equalTo 9
+		}
+	}
+
+	override fun mouseClicked(point: Point, mouseButton: MouseButton): Boolean {
+		return if (mouseButton == MouseButton.LEFT || mouseButton == MouseButton.RIGHT) {
+			showDropdown()
+			true
+		} else {
+			super.mouseClicked(point, mouseButton)
+		}
+	}
+
+	private fun showDropdown() {
+//		val dropdownWindow = window.screen.addWindow(Window())
+//		val dropdownBackground = dropdownWindow.addView(NinePatchView(NinePatchTexture.BUTTON_BG).apply {
+//			zIndex = -1.0
+//		})
+//		val stack = dropdownWindow.addView(StackView(Axis.VERTICAL, StackView.Distribution.FILL))
+//		lateinit var selectedButton: View
+//		val buttons = mutableListOf<Button>()
+//		val last = allValues.count() - 1
+//		for ((index, value) in allValues.withIndex()) {
+//			val contentView = createView(value)
+//			val button = stack.addArrangedSubview(Button(contentView, padding).apply {
+//				background = null
+//				hoveredBackground = DropdownItemBackgroundView(index == 0, index == last, NinePatchTexture.BUTTON_HOVERED_BG)
+//				disabledBackground = DropdownItemBackgroundView(index == 0, index == last, NinePatchTexture.BUTTON_DISABLED_BG)
+//				disabled = value == this@DropdownButton.value
+//				handler = {
+//					dropdownWindow.removeFromScreen()
+//					valueSelected(value)
+//				}
+//			})
+//			if (value == this@DropdownButton.value) {
+//				selectedButton = button
+//			}
+//			buttons.add(button)
+//			dropdownWindow.solver.dsl {
+//				if (button.content.intrinsicContentSize != null) {
+//					button.widthAnchor greaterThanOrEqualTo button.content.intrinsicContentSize!!.width + 2 * button.padding
+//				}
+//			}
+//		}
+//		dropdownWindow.solver.dsl {
+//			// constrain to the DropdownButton anchor's value constant, because we're crossing windows and
+//			// therefore solvers, which isn't allowed
+//			stack.leftAnchor equalTo this@DropdownButton.rightAnchor.value
+//			selectedButton.centerYAnchor equalTo this@DropdownButton.centerYAnchor.value
+//
+//			dropdownBackground.leftAnchor equalTo stack.leftAnchor
+//			dropdownBackground.rightAnchor equalTo stack.rightAnchor
+//			dropdownBackground.topAnchor equalTo stack.topAnchor
+//			dropdownBackground.bottomAnchor equalTo stack.bottomAnchor
+//		}
+//		dropdownWindow.layout()
+	}
+
+	private fun valueSelected(value: Value) {
+		this.value = value
+		handler?.invoke(this)
+	}
+
+}
+
+private class DropdownItemBackgroundView(
+		private val first: Boolean,
+		private val last: Boolean,
+		ninePatch: NinePatchTexture
+): NinePatchView(ninePatch) {
+
+	// Corners
+	private val topLeftDelegate = ResettableLazyProperty {
+		super.topLeft
+		Rect(0.0, 0.0, ninePatch.cornerWidth.toDouble(), if (first) ninePatch.cornerHeight.toDouble() else 0.0)
+	}
+	override val topLeft by topLeftDelegate
+
+	private val topRightDelegate = ResettableLazyProperty {
+		Rect(bounds.width - ninePatch.cornerWidth, 0.0, topLeft.width, topLeft.height)
+	}
+	override val topRight by topRightDelegate
+
+	private val bottomLeftDelegate = ResettableLazyProperty {
+		Rect(topLeft.left, bounds.height - ninePatch.cornerHeight, topLeft.width, if (last) ninePatch.cornerHeight.toDouble() else 0.0)
+	}
+	override val bottomLeft by bottomLeftDelegate
+
+	private val bottomRightDelegate = ResettableLazyProperty {
+		Rect(topRight.left, bottomLeft.top, topLeft.width, bottomLeft.height)
+	}
+	override val bottomRight by bottomRightDelegate
+
+	// Edges
+	private val topMiddleDelegate = ResettableLazyProperty {
+		Rect(ninePatch.cornerWidth.toDouble(), topLeft.top, bounds.width - 2 * ninePatch.cornerWidth, topLeft.height)
+	}
+	override val topMiddle by topMiddleDelegate
+
+	private val bottomMiddleDelegate = ResettableLazyProperty {
+		Rect(topMiddle.left, bottomLeft.top, topMiddle.width, bottomLeft.height)
+	}
+	override val bottomMiddle by bottomMiddleDelegate
+
+	private val leftMiddleDelegate = ResettableLazyProperty {
+		Rect(topLeft.left, topLeft.bottom, topLeft.width, bounds.height - (if (first && last) 2 else if (first || last) 1 else 0) * ninePatch.cornerHeight)
+	}
+	override val leftMiddle by leftMiddleDelegate
+
+	private val rightMiddleDelegate = ResettableLazyProperty {
+		Rect(topRight.left, topRight.bottom, topRight.width, leftMiddle.height)
+	}
+	override val rightMiddle by rightMiddleDelegate
+
+	// Center
+	private val centerDelegate = ResettableLazyProperty {
+		Rect(topLeft.right, topMiddle.bottom, topMiddle.width, leftMiddle.height)
+	}
+	override val center by centerDelegate
+
+	private val delegates = listOf(topLeftDelegate, topRightDelegate, bottomLeftDelegate, bottomRightDelegate, topMiddleDelegate, bottomMiddleDelegate, leftMiddleDelegate, rightMiddleDelegate, centerDelegate)
+
+	override fun didLayout() {
+		super.didLayout()
+
+		delegates.forEach(ResettableLazyProperty<Rect>::reset)
+	}
+
+}

src/main/kotlin/net/shadowfacts/cacao/view/button/EnumButton.kt

@@ -0,0 +1,45 @@
+package net.shadowfacts.cacao.view.button
+
+import net.shadowfacts.cacao.geometry.Point
+import net.shadowfacts.cacao.util.EnumHelper
+import net.shadowfacts.cacao.util.MouseButton
+import net.shadowfacts.cacao.view.Label
+
+/**
+ * A button that cycles through enum values.
+ * Left click: forwards
+ * Right click: backwards
+ * All other mouse buttons call the handler with the unchanged value
+ *
+ * @author shadowfacts
+ * @param initialValue The initial enum value for this button.
+ * @param localizer A function that takes an enum value and converts into a string for the button's label.
+ */
+class EnumButton<E: Enum<E>>(initialValue: E, val localizer: (E) -> String): AbstractButton<EnumButton<E>>(Label(localizer(initialValue))) {
+
+	private val label: Label
+		get() = content as Label
+
+	/**
+	 * The current value of the enum button.
+	 * Updating this property will use the [localizer] to update the label.
+	 */
+	var value: E = initialValue
+		set(value) {
+			field = value
+			label.text = localizer(value)
+		}
+
+	override fun mouseClicked(point: Point, mouseButton: MouseButton): Boolean {
+		if (!disabled) {
+			value = when (mouseButton) {
+				MouseButton.LEFT -> EnumHelper.next(value)
+				MouseButton.RIGHT -> EnumHelper.previous(value)
+				else -> value
+			}
+		}
+
+		return super.mouseClicked(point, mouseButton)
+	}
+
+}

src/main/kotlin/net/shadowfacts/cacao/view/button/ToggleButton.kt

@@ -0,0 +1,46 @@
+package net.shadowfacts.cacao.view.button
+
+import net.minecraft.util.Identifier
+import net.shadowfacts.cacao.geometry.Point
+import net.shadowfacts.cacao.geometry.Size
+import net.shadowfacts.cacao.util.MouseButton
+import net.shadowfacts.cacao.util.texture.Texture
+import net.shadowfacts.cacao.view.TextureView
+
+/**
+ * A button for toggling between on/off states.
+ *
+ * @author shadowfacts
+ * @param initialState Whether the button starts as on or off.
+ */
+class ToggleButton(initialState: Boolean): AbstractButton<ToggleButton>(TextureView(if (initialState) ON else OFF).apply {
+	intrinsicContentSize = Size(19.0, 19.0)
+}, padding = 0.0) {
+
+	companion object {
+		val ON = Texture(Identifier("asmr", "textures/gui/toggle.png"), 0, 0)
+		val OFF = Texture(Identifier("asmr", "textures/gui/toggle.png"), 0, 19)
+	}
+
+	private val textureView: TextureView
+		get() = content as TextureView
+
+	/**
+	 * The button's current on/off state.
+	 * Updating this property updates the button's texture.
+	 */
+	var state: Boolean = initialState
+		set(value) {
+			field = value
+			textureView.texture = if (value) ON else OFF
+		}
+
+	override fun mouseClicked(point: Point, mouseButton: MouseButton): Boolean {
+		if (!disabled && (mouseButton == MouseButton.LEFT || mouseButton == MouseButton.RIGHT)) {
+			state = !state
+		}
+
+		return super.mouseClicked(point, mouseButton)
+	}
+
+}

src/main/kotlin/net/shadowfacts/cacao/viewcontroller/ViewController.kt

@@ -0,0 +1,192 @@
+package net.shadowfacts.cacao.viewcontroller
+
+import net.shadowfacts.cacao.Window
+import net.shadowfacts.cacao.util.properties.ObservableLazyProperty
+import net.shadowfacts.cacao.view.View
+import net.shadowfacts.kiwidsl.dsl
+import java.lang.RuntimeException
+import java.util.*
+
+/**
+ * The base Cacao View Controller class. A view controller is an object that owns and manages a [View].
+ *
+ * The view controller receives lifecycle callbacks for its view.
+ *
+ * @author shadowfacts
+ */
+abstract class ViewController {
+
+	/**
+	 * The window that contains this view controller.
+	 * This property is not set until either:
+	 * a) a [Window] is initialized with this VC as it's root view controller or
+	 * b) this VC is added as a child of another view controller.
+	 */
+	var window: Window? = null
+
+	/**
+	 * Helper function for creating layout constraints in the domain of this VC's window.
+	 * This function is not usable until [window] is initialized.
+	 */
+	val createConstraints
+		get() = window!!.solver::dsl
+
+	/**
+	 * The view that this View Controller has.
+	 * This property is created by [loadView] and is not initialized before that method has been called.
+	 *
+	 * @see loadView
+	 */
+	lateinit var view: View
+		protected set
+
+	/**
+	 * This VC's parent view controller. If `null`, this VC is the root view controller of its [window].
+	 */
+	var parent: ViewController? = null
+		set(value) {
+			willMoveTo(value)
+			field = value
+			didMoveTo(value)
+		}
+
+	// _children is the internal, mutable object since we only want it to be mutated by the embed/removeChild methods
+	private var _children = LinkedList<ViewController>()
+	/**
+	 * The list of all the child VCs of this view controller.
+	 * This list should never be mutated directly, only by the [embedChild]/[removeChild] methods.
+	 */
+	val children: List<ViewController> = _children
+
+	/**
+	 * This method somehow loads a [View] and sets this VC's [view] property to it.
+	 *
+	 * This method should only be called by the framework. After the [view] property is set, the framework is
+	 * responsible for initializing its [View.window]/[View.solver] properties and calling [View.wasAdded].
+	 *
+	 * The default implementation simply creates a [View] and does nothing else with it.
+	 */
+	open fun loadView() {
+		view = View()
+	}
+
+	/**
+	 * This method is called after the view is loaded, it's properties are initialized, and [View.wasAdded] has been
+	 * called.
+	 */
+	open fun viewDidLoad() {}
+
+	/**
+	 * This method is called immediately before the [Window.solver] is going to solve constraints and update variables.
+	 * If overridden, the superclass method must be called.
+	 */
+	open fun viewWillLayoutSubviews() {
+		children.forEach(ViewController::viewWillLayoutSubviews)
+	}
+
+	/**
+	 * This method is called immediately after the [Window.solver] has solved constraints and variables have been updated.
+	 * This method is responsible for invoking the VC's [View.didLayout] method.
+	 * If overridden, the superclass method must be called.
+	 */
+	open fun viewDidLayoutSubviews() {
+		view.didLayout()
+		children.forEach(ViewController::viewDidLayoutSubviews)
+	}
+
+	/**
+	 * Called when the VC's view has been added to the screen and is about to be displayed.
+	 */
+	open fun viewWillAppear() {
+		children.forEach(ViewController::viewWillAppear)
+	}
+
+	/**
+	 * Called immediately after the VC's view has first been displayed on screen.
+	 */
+	open fun viewDidAppear() {
+		children.forEach(ViewController::viewDidAppear)
+	}
+
+	/**
+	 * Called before the view will disappear from the screen, either because the VC has been removed from it's parent/screen
+	 * or because the [net.shadowfacts.cacao.CacaoScreen] has been closed.
+	 */
+	open fun viewWillDisappear() {
+		children.forEach(ViewController::viewWillDisappear)
+	}
+
+	/**
+	 * Called after the view has disappeared from the screen.
+	 */
+	open fun viewDidDisappear() {
+		children.forEach(ViewController::viewDidDisappear)
+	}
+
+	/**
+	 * Called before the view controller's parent changes to the given new value.
+	 *
+	 * @param parent The new parent view controller.
+	 */
+	open fun willMoveTo(parent: ViewController?) {}
+
+	/**
+	 * Called after the view controller's parent has changed to the given new value.
+	 *
+	 * @param parent The new parent view controller.
+	 */
+	open fun didMoveTo(parent: ViewController?) {}
+
+	/**
+	 * Embeds a child view controller in this VC.
+	 *
+	 * @param viewController The new child VC.
+	 * @param container The view that will be used as the superview for the child VC's view. Defaults to this VC's [view].
+	 * @param pinEdges Whether the edges of the child VC will be pinned (constrained to be equal to) the container's edges.
+	 * 					Defaults to `true`.
+	 */
+	fun embedChild(viewController: ViewController, container: View = this.view, pinEdges: Boolean = true) {
+		viewController.parent = this
+		viewController.window = window
+		_children.add(viewController)
+		viewController.loadView()
+
+		container.addSubview(viewController.view)
+
+		if (pinEdges) {
+			createConstraints {
+				viewController.view.leftAnchor equalTo container.leftAnchor
+				viewController.view.rightAnchor equalTo container.rightAnchor
+				viewController.view.topAnchor equalTo container.topAnchor
+				viewController.view.bottomAnchor equalTo container.bottomAnchor
+			}
+		}
+
+		viewController.viewDidLoad()
+	}
+
+	/**
+	 * Removes the given view controller
+	 *
+	 * @param viewController The child VC to remove from this view controller.
+	 * @throws RuntimeException If the given [viewController] is not a child of this VC.
+	 */
+	fun removeChild(viewController: ViewController) {
+		if (viewController.parent != this) {
+			throw RuntimeException("Cannot remove child view controller whose parent is not this view controller")
+		}
+
+		viewController.parent = null
+		_children.remove(viewController)
+	}
+
+	/**
+	 * Removes this view controller from its parent, if it has one.
+	 */
+	fun removeFromParent() {
+		parent?.removeChild(this)
+		view.removeFromSuperview()
+		// todo: remove view from superview
+	}
+
+}

src/main/kotlin/net/shadowfacts/kiwidsl/KiwiDSL.kt

@@ -0,0 +1,103 @@
+package net.shadowfacts.kiwidsl
+
+import no.birkett.kiwi.*
+
+/**
+ * @author shadowfacts
+ */
+class KiwiContext(val solver: Solver) {
+	val REQUIRED = Strength.REQUIRED
+	val STRONG = Strength.STRONG
+	val MEDIUM = Strength.MEDIUM
+	val WEAK = Strength.WEAK
+
+	// Constraints
+	infix fun ExpressionConvertible.equalTo(other: ExpressionConvertible): Constraint {
+		return Symbolics.equals(this.toExpression(), other.toExpression()).apply(solver::addConstraint)
+	}
+
+	fun ExpressionConvertible.equalTo(other: ExpressionConvertible, strength: Double): Constraint {
+		return Symbolics.equals(this.toExpression(), other.toExpression()).setStrength(strength).apply(solver::addConstraint)
+	}
+
+	infix fun ExpressionConvertible.equalTo(constant: Number): Constraint {
+		return Symbolics.equals(this.toExpression(), constant.toDouble()).apply(solver::addConstraint)
+	}
+
+	fun ExpressionConvertible.equalTo(constant: Number, strength: Double): Constraint {
+		return Symbolics.equals(this.toExpression(), constant.toDouble()).setStrength(strength).apply(solver::addConstraint)
+	}
+
+	infix fun ExpressionConvertible.lessThanOrEqualTo(other: ExpressionConvertible): Constraint {
+		return Symbolics.lessThanOrEqualTo(this.toExpression(), other.toExpression()).apply(solver::addConstraint)
+	}
+
+	fun ExpressionConvertible.lessThanOrEqualTo(other: ExpressionConvertible, strength: Double): Constraint {
+		return Symbolics.lessThanOrEqualTo(this.toExpression(), other.toExpression()).setStrength(strength).apply(solver::addConstraint)
+	}
+
+	infix fun ExpressionConvertible.lessThanOrEqualTo(constant: Number): Constraint {
+		return Symbolics.lessThanOrEqualTo(this.toExpression(), constant.toDouble()).apply(solver::addConstraint)
+	}
+
+	fun ExpressionConvertible.lessThanOrEqualTo(constant: Number, strength: Double): Constraint {
+		return Symbolics.lessThanOrEqualTo(this.toExpression(), constant.toDouble()).setStrength(strength).apply(solver::addConstraint)
+	}
+
+	infix fun ExpressionConvertible.greaterThanOrEqualTo(other: ExpressionConvertible): Constraint {
+		return Symbolics.greaterThanOrEqualTo(this.toExpression(), other.toExpression()).apply(solver::addConstraint)
+	}
+
+	fun ExpressionConvertible.greaterThanOrEqualTo(other: ExpressionConvertible, strength: Double): Constraint {
+		return Symbolics.greaterThanOrEqualTo(this.toExpression(), other.toExpression()).setStrength(strength).apply(solver::addConstraint)
+	}
+
+	infix fun ExpressionConvertible.greaterThanOrEqualTo(constant: Number): Constraint {
+		return Symbolics.greaterThanOrEqualTo(this.toExpression(), constant.toDouble()).apply(solver::addConstraint)
+	}
+
+	fun ExpressionConvertible.greaterThanOrEqualTo(constant: Number, strength: Double): Constraint {
+		return Symbolics.greaterThanOrEqualTo(this.toExpression(), constant.toDouble()).setStrength(strength).apply(solver::addConstraint)
+	}
+
+	// Addition
+	operator fun ExpressionConvertible.plus(other: ExpressionConvertible): Expression {
+		return Symbolics.add(this.toExpression(), other.toExpression())
+	}
+
+	operator fun ExpressionConvertible.plus(constant: Number): Expression {
+		return Symbolics.add(this.toExpression(), constant.toDouble())
+	}
+
+	// Subtraction
+	operator fun ExpressionConvertible.minus(other: ExpressionConvertible): Expression {
+		return Symbolics.subtract(this.toExpression(), other.toExpression())
+	}
+
+	operator fun ExpressionConvertible.minus(constant: Number): Expression {
+		return Symbolics.subtract(this.toExpression(), constant.toDouble())
+	}
+
+	// Multiplication
+	operator fun ExpressionConvertible.times(other: ExpressionConvertible): Expression {
+		return Symbolics.multiply(this.toExpression(), other.toExpression())
+	}
+
+	operator fun ExpressionConvertible.times(constant: Number): Expression {
+		return Symbolics.multiply(this.toExpression(), constant.toDouble())
+	}
+
+	// Division
+	operator fun ExpressionConvertible.div(other: ExpressionConvertible): Expression {
+		return Symbolics.divide(this.toExpression(), other.toExpression())
+	}
+
+	operator fun ExpressionConvertible.div(constant: Number): Expression {
+		return Symbolics.divide(this.toExpression(), constant.toDouble())
+	}
+}
+
+fun Solver.dsl(init: KiwiContext.() -> Unit): Solver {
+	KiwiContext(this).init()
+	return this
+}

src/main/kotlin/net/shadowfacts/phycon/screen/TestCacaoScreen.kt

@@ -0,0 +1,56 @@
+package net.shadowfacts.phycon.screen
+
+import net.minecraft.util.Identifier
+import net.shadowfacts.cacao.CacaoScreen
+import net.shadowfacts.cacao.Window
+import net.shadowfacts.cacao.geometry.Axis
+import net.shadowfacts.cacao.geometry.Size
+import net.shadowfacts.cacao.util.Color
+import net.shadowfacts.cacao.util.texture.NinePatchTexture
+import net.shadowfacts.cacao.util.texture.Texture
+import net.shadowfacts.cacao.view.NinePatchView
+import net.shadowfacts.cacao.view.StackView
+import net.shadowfacts.cacao.view.TextureView
+import net.shadowfacts.cacao.view.View
+import net.shadowfacts.cacao.viewcontroller.ViewController
+import net.shadowfacts.kiwidsl.dsl
+
+/**
+ * @author shadowfacts
+ */
+class TestCacaoScreen: CacaoScreen() {
+
+	init {
+		val viewController = object: ViewController() {
+			override fun loadView() {
+				view = View()
+			}
+
+			override fun viewDidLoad() {
+				super.viewDidLoad()
+
+				val stack = view.addSubview(StackView(Axis.VERTICAL, StackView.Distribution.CENTER, spacing = 4.0)).apply {
+					backgroundColor = Color.WHITE
+				}
+				val birch = stack.addArrangedSubview(TextureView(Texture(Identifier("textures/block/birch_log_top.png"), 0, 0, 16, 16))).apply {
+					intrinsicContentSize = Size(50.0, 50.0)
+				}
+				val ninePatch = stack.addArrangedSubview(NinePatchView(NinePatchTexture.PANEL_BG)).apply {
+					intrinsicContentSize = Size(75.0, 100.0)
+				}
+				val red = stack.addArrangedSubview(View()).apply {
+					intrinsicContentSize = Size(50.0, 50.0)
+					backgroundColor = Color.RED
+				}
+
+				view.solver.dsl {
+					stack.topAnchor equalTo 0
+					stack.centerXAnchor equalTo window!!.centerXAnchor
+					stack.widthAnchor equalTo 100
+				}
+			}
+		}
+		addWindow(Window(viewController))
+	}
+
+}

src/test/kotlin/net/shadowfacts/cacao/CoordinateConversionTests.kt

@@ -0,0 +1,90 @@
+package net.shadowfacts.cacao
+
+import net.shadowfacts.cacao.geometry.Point
+import net.shadowfacts.cacao.geometry.Rect
+import net.shadowfacts.cacao.view.View
+import net.shadowfacts.cacao.viewcontroller.ViewController
+import org.junit.jupiter.api.Assertions.assertEquals
+import org.junit.jupiter.api.BeforeEach
+import org.junit.jupiter.api.Test
+
+/**
+ * @author shadowfacts
+ */
+class CoordinateConversionTests {
+
+	lateinit var screen: CacaoScreen
+	lateinit var viewController: ViewController
+	lateinit var window: Window
+	
+	val view: View
+		get() = viewController.view
+
+	@BeforeEach
+	fun setup() {
+		screen = CacaoScreen()
+		viewController = object: ViewController() {
+			override fun loadView() {
+				view = View(Rect(0.0, 0.0, 1000.0, 1000.0))
+			}
+		}
+		window = screen.addWindow(Window(viewController))
+	}
+
+	@Test
+	fun testConvertToParent() {
+		val a = view.addSubview(View(Rect(0.0, 0.0, 100.0, 100.0)))
+		val b = a.addSubview(View(Rect(25.0, 25.0, 50.0, 50.0)))
+
+		assertEquals(Point(25.0, 25.0), b.convert(Point(0.0, 0.0), to = a))
+		assertEquals(Point(75.0, 75.0), b.convert(Point(50.0, 50.0), to = a))
+		assertEquals(Rect(25.0, 25.0, 50.0, 50.0), b.convert(Rect(0.0, 0.0, 50.0, 50.0), to = a))
+	}
+
+	@Test
+	fun testConvertToSibling() {
+		val root = view.addSubview(View(Rect(0.0, 0.0, 200.0, 200.0)))
+		val a = root.addSubview(View(Rect(25.0, 25.0, 50.0, 50.0)))
+		val b = root.addSubview(View(Rect(75.0, 75.0, 50.0, 50.0)))
+
+		assertEquals(Point(-50.0, -50.0), a.convert(Point(0.0, 0.0), to = b))
+		assertEquals(Point(100.0, 100.0), b.convert(Point(50.0, 50.0), to = a))
+		assertEquals(Rect(50.0, 50.0, 50.0, 50.0), b.convert(Rect(0.0, 0.0, 50.0, 50.0), to = a))
+	}
+
+	@Test
+	fun testConvertBetweenSubtrees() {
+		val root = view.addSubview(View(Rect(0.0, 0.0, 200.0, 100.0)))
+		val a = root.addSubview(View(Rect(0.0, 0.0, 100.0, 100.0)))
+		val b = root.addSubview(View(Rect(100.0, 0.0, 100.0, 100.0)))
+		val c = a.addSubview(View(Rect(0.0, 0.0, 50.0, 50.0)))
+		val d = b.addSubview(View(Rect(0.0, 0.0, 50.0, 50.0)))
+
+		assertEquals(Point(-100.0, 0.0), c.convert(Point(0.0, 0.0), to = b))
+		assertEquals(Point(-50.0, 50.0), c.convert(Point(50.0, 50.0), to = d))
+		assertEquals(Rect(100.0, 0.0, 50.0, 50.0), d.convert(Rect(0.0, 0.0, 50.0, 50.0), to = c))
+	}
+
+	@Test
+	fun testConvertBetweenTopLevelViews() {
+		val a = view.addSubview(View(Rect(0.0, 0.0, 100.0, 100.0)))
+		val b = view.addSubview(View(Rect(100.0, 100.0, 100.0, 100.0)))
+
+		assertEquals(Point(0.0, 0.0), a.convert(Point(100.0, 100.0), to = b))
+		assertEquals(Point(200.0, 200.0), b.convert(Point(100.0, 100.0), to = a))
+		assertEquals(Rect(100.0, 100.0, 100.0, 100.0), b.convert(Rect(0.0, 0.0, 100.0, 100.0), to = a))
+	}
+
+	@Test
+	fun testConvertBetweenTopLevelSubtrees() {
+		val a = view.addSubview(View(Rect(0.0, 0.0, 100.0, 100.0)))
+		val b = view.addSubview(View(Rect(100.0, 100.0, 100.0, 100.0)))
+		val c = a.addSubview(View(Rect(25.0, 25.0, 50.0, 50.0)))
+		val d = b.addSubview(View(Rect(25.0, 25.0, 50.0, 50.0)))
+
+		assertEquals(Point(-50.0, -50.0), c.convert(Point(50.0, 50.0), to = d))
+		assertEquals(Point(100.0, 100.0), d.convert(Point(0.0, 0.0), to = c))
+		assertEquals(Rect(100.0, 100.0, 50.0, 50.0), d.convert(Rect(0.0, 0.0, 50.0, 50.0), to = c))
+	}
+
+}

src/test/kotlin/net/shadowfacts/cacao/WindowLayoutTests.kt

@@ -0,0 +1,95 @@
+package net.shadowfacts.cacao
+
+import net.shadowfacts.cacao.geometry.Rect
+import net.shadowfacts.kiwidsl.dsl
+import net.shadowfacts.cacao.geometry.Size
+import net.shadowfacts.cacao.view.View
+import net.shadowfacts.cacao.viewcontroller.ViewController
+import org.junit.jupiter.api.Assertions.*
+import org.junit.jupiter.api.BeforeEach
+import org.junit.jupiter.api.Test
+
+/**
+ * @author shadowfacts
+ */
+class WindowLayoutTests {
+
+	lateinit var screen: CacaoScreen
+	lateinit var viewController: ViewController
+	lateinit var window: Window
+
+	val view: View
+		get() = viewController.view
+
+	@BeforeEach
+	fun setup() {
+		screen = CacaoScreen()
+		viewController = object: ViewController() {
+			override fun loadView() {
+				view = View(Rect(0.0, 0.0, 1000.0, 1000.0))
+			}
+		}
+		window = screen.addWindow(Window(viewController))
+	}
+
+	@Test
+	fun testConstraintToConstant() {
+		val view = view.addSubview(View())
+		window.solver.dsl {
+			view.leftAnchor equalTo 100
+			view.rightAnchor equalTo 200
+
+			view.topAnchor equalTo 100
+			view.heightAnchor equalTo 200
+		}
+		window.layout()
+
+		assertEquals(100.0, view.widthAnchor.value)
+		assertEquals(300.0, view.bottomAnchor.value)
+	}
+
+	@Test
+	fun testConstraintToView() {
+		val one = view.addSubview(View())
+		val two = view.addSubview(View())
+		window.solver.dsl {
+			one.leftAnchor equalTo 0
+			one.widthAnchor equalTo 100
+
+			one.topAnchor equalTo 0
+			one.heightAnchor equalTo 200
+
+			two.leftAnchor equalTo one.rightAnchor
+			two.rightAnchor equalTo 400
+
+			two.topAnchor equalTo one.bottomAnchor
+			two.heightAnchor equalTo one.heightAnchor
+		}
+		window.layout()
+
+		assertEquals(100.0, two.leftAnchor.value)
+		assertEquals(300.0, two.widthAnchor.value)
+
+		assertEquals(200.0, two.topAnchor.value)
+		assertEquals(400.0, two.bottomAnchor.value)
+	}
+
+	@Test
+	fun testIntrinsicContentSize() {
+		val view = view.addSubview(View()).apply {
+			intrinsicContentSize = Size(100.0, 200.0)
+		}
+		window.solver.dsl {
+			view.leftAnchor equalTo 0
+			view.topAnchor equalTo 100
+		}
+		window.layout()
+
+		assertEquals(100.0, view.widthAnchor.value)
+		assertEquals(100.0, view.rightAnchor.value)
+
+		assertEquals(200.0, view.heightAnchor.value)
+		assertEquals(300.0, view.bottomAnchor.value)
+	}
+
+}

src/test/kotlin/net/shadowfacts/cacao/geometry/RectTest.kt

@@ -0,0 +1,39 @@
+package net.shadowfacts.cacao.geometry
+
+import org.junit.jupiter.api.Assertions.*
+import org.junit.jupiter.api.Test
+
+/**
+ * @author shadowfacts
+ */
+class RectTest {
+
+	@Test
+	fun testTrailingEdges() {
+		val rect = Rect(25.0, 50.0, 100.0, 200.0)
+		assertEquals(125.0, rect.right)
+		assertEquals(250.0, rect.bottom)
+	}
+
+	@Test
+	fun testCenter() {
+		val rect = Rect(25.0, 50.0, 100.0, 200.0)
+		assertEquals(75.0, rect.midX)
+		assertEquals(150.0, rect.midY)
+
+	}
+
+	@Test
+	fun testPoints() {
+		val rect = Rect(25.0, 50.0, 100.0, 200.0)
+		assertEquals(Point(25.0, 50.0), rect.origin)
+		assertEquals(Point(75.0, 150.0), rect.center)
+	}
+
+	@Test
+	fun testSize() {
+		val rect = Rect(25.0, 50.0, 100.0, 200.0)
+		assertEquals(Size(100.0, 200.0), rect.size)
+	}
+
+}

src/test/kotlin/net/shadowfacts/cacao/util/ColorTest.kt

@@ -0,0 +1,25 @@
+package net.shadowfacts.cacao.util
+
+import org.junit.jupiter.api.Assertions.*
+import org.junit.jupiter.api.Test
+
+/**
+ * @author shadowfacts
+ */
+class ColorTest {
+
+	@Test
+	fun fromRGB() {
+		val color = Color(0x123456)
+		assertEquals(0x12, color.red)
+		assertEquals(0x34, color.green)
+		assertEquals(0x56, color.blue)
+	}
+
+	@Test
+	fun toARGB() {
+		val color = Color(red = 0x12, green = 0x34, blue = 0x56, alpha = 0x78)
+		assertEquals(0x78123456, color.argb)
+	}
+
+}

src/test/kotlin/net/shadowfacts/cacao/util/EnumHelperTests.kt

@@ -0,0 +1,27 @@
+package net.shadowfacts.cacao.util
+
+import org.junit.jupiter.api.Assertions.assertEquals
+import org.junit.jupiter.api.Test
+
+/**
+ * @author shadowfacts
+ */
+class EnumHelperTests {
+
+	enum class MyEnum {
+		ONE, TWO
+	}
+
+	@Test
+	fun testNext() {
+		assertEquals(MyEnum.TWO, EnumHelper.next(MyEnum.ONE))
+		assertEquals(MyEnum.ONE, EnumHelper.next(MyEnum.TWO))
+	}
+
+	@Test
+	fun testPrev() {
+		assertEquals(MyEnum.ONE, EnumHelper.previous(MyEnum.TWO))
+		assertEquals(MyEnum.TWO, EnumHelper.previous(MyEnum.ONE))
+	}
+
+}

src/test/kotlin/net/shadowfacts/cacao/util/LCATest.kt

@@ -0,0 +1,73 @@
+package net.shadowfacts.cacao.util
+
+import org.junit.jupiter.api.Assertions.assertEquals
+import org.junit.jupiter.api.Assertions.assertNull
+import org.junit.jupiter.api.Test
+
+/**
+ * @author shadowfacts
+ */
+class LCATest {
+
+	class Node(val name: String, val parent: Node?)
+
+	@Test
+	fun testDirectParent() {
+		val parent = Node("parent", null)
+		val child = Node("child", parent)
+		assertEquals(parent, LowestCommonAncestor.find(parent, child, Node::parent))
+		assertEquals(parent, LowestCommonAncestor.find(child, parent, Node::parent))
+	}
+
+	@Test
+	fun testSiblings() {
+		val root = Node("root", null)
+		val a = Node("a", root)
+		val b = Node("b", root)
+		assertEquals(root, LowestCommonAncestor.find(a, b, Node::parent))
+	}
+
+	@Test
+	fun testBetweenSubtrees() {
+		//          ┌────┐
+		//          │root│
+		//          └────┘
+		//         ╱      ╲
+		//        ╱        ╲
+		//     ┌─┐          ┌─┐
+		//     │A│          │B│
+		//     └─┘          └─┘
+		//    ╱   ╲        ╱   ╲
+		//   ╱     ╲      ╱     ╲
+		// ┌─┐       ┌─┐┌─┐       ┌─┐
+		// │C│       │D││E│       │F│
+		// └─┘       └─┘└─┘       └─┘
+		val root = Node("root", null)
+
+		val a = Node("a", root)
+		val c = Node("c", a)
+		val d = Node("d", a)
+
+		val b = Node("b", root)
+		val e = Node("e", b)
+		val f = Node("f", b)
+
+		assertEquals(a, LowestCommonAncestor.find(c, d, Node::parent))
+		assertEquals(root, LowestCommonAncestor.find(c, b, Node::parent))
+		assertEquals(root, LowestCommonAncestor.find(d, e, Node::parent))
+		assertEquals(root, LowestCommonAncestor.find(c, root, Node::parent))
+	}
+
+	@Test
+	fun testBetweenDisjointTrees() {
+		val a = Node("a", null)
+		val b = Node("b", a)
+
+		val c = Node("c", null)
+		val d = Node("d", c)
+
+		assertNull(LowestCommonAncestor.find(a, d, Node::parent))
+		assertNull(LowestCommonAncestor.find(b, c, Node::parent))
+	}
+
+}

src/test/kotlin/net/shadowfacts/cacao/util/properties/ObservableLateInitPropertyTests.kt

@@ -0,0 +1,33 @@
+package net.shadowfacts.cacao.util.properties
+
+import org.junit.jupiter.api.Assertions.*
+import org.junit.jupiter.api.Test
+import java.util.concurrent.CompletableFuture
+
+/**
+ * @author shadowfacts
+ */
+class ObservableLateInitPropertyTests {
+
+	class MyClass(callback: (String) -> Unit) {
+		val delegate = ObservableLateInitProperty(callback)
+		var prop by delegate
+	}
+
+	@Test
+	fun testObservation() {
+		val future = CompletableFuture<String>()
+		val obj = MyClass { future.complete(it) }
+		obj.prop = "test"
+		assertEquals("test", future.getNow(null))
+	}
+
+	@Test
+	fun testIsInitialized() {
+		val obj = MyClass {}
+		assertFalse(obj.delegate.isInitialized)
+		obj.prop = "test"
+		assertTrue(obj.delegate.isInitialized)
+	}
+
+}

src/test/kotlin/net/shadowfacts/cacao/util/properties/ResettableLazyPropertyTests.kt

@@ -0,0 +1,35 @@
+package net.shadowfacts.cacao.util.properties
+
+import org.junit.jupiter.api.Assertions.*
+import org.junit.jupiter.api.Test
+
+/**
+ * @author shadowfacts
+ */
+class ResettableLazyPropertyTests {
+
+	class MyClass {
+		var iteration = 1
+		val delegate = ResettableLazyProperty { "test ${iteration++}" }
+		val prop by delegate
+	}
+
+	@Test
+	fun testResets() {
+		val obj = MyClass()
+		assertEquals("test 1", obj.prop)
+		obj.delegate.reset()
+		assertEquals("test 2", obj.prop)
+		assertEquals("test 2", obj.prop)
+	}
+
+	@Test
+	fun testIsInitialized() {
+		val obj = MyClass()
+		assertFalse(obj.delegate.isInitialized)
+		assertEquals("test 1", obj.prop)
+		assertTrue(obj.delegate.isInitialized)
+		obj.delegate.reset()
+		assertFalse(obj.delegate.isInitialized)
+	}
+}

src/test/kotlin/net/shadowfacts/cacao/view/StackViewLayoutTests.kt

@@ -0,0 +1,261 @@
+package net.shadowfacts.cacao.view
+
+import net.shadowfacts.cacao.CacaoScreen
+import net.shadowfacts.kiwidsl.dsl
+import net.shadowfacts.cacao.Window
+import net.shadowfacts.cacao.geometry.Axis
+import net.shadowfacts.cacao.geometry.Rect
+import net.shadowfacts.cacao.geometry.Size
+import net.shadowfacts.cacao.viewcontroller.ViewController
+import org.junit.jupiter.api.Assertions.assertEquals
+import org.junit.jupiter.api.BeforeEach
+import org.junit.jupiter.api.Test
+import kotlin.math.abs
+
+/**
+ * @author shadowfacts
+ */
+class StackViewLayoutTests {
+
+	lateinit var screen: CacaoScreen
+	lateinit var viewController: ViewController
+	lateinit var window: Window
+	
+	val view: View
+		get() = viewController.view
+
+	@BeforeEach
+	fun setup() {
+		screen = CacaoScreen()
+		viewController = object: ViewController() {
+			override fun loadView() {
+				view = View(Rect(0.0, 0.0, 1000.0, 1000.0))
+			}
+		}
+		window = screen.addWindow(Window(viewController))
+	}
+
+	@Test
+	fun testVerticalLayout() {
+		val stack = view.addSubview(StackView(Axis.VERTICAL))
+		val one = stack.addArrangedSubview(View().apply {
+			intrinsicContentSize = Size(50.0, 50.0)
+		})
+		val two = stack.addArrangedSubview(View().apply {
+			intrinsicContentSize = Size(75.0, 75.0)
+		})
+		val three = stack.addArrangedSubview(View().apply {
+			intrinsicContentSize = Size(50.0, 50.0)
+		})
+		window.solver.dsl {
+			stack.topAnchor equalTo 0
+		}
+		window.layout()
+
+		assertEquals(0.0, abs(one.topAnchor.value)) // sometimes -0.0, which fails the assertion but is actually ok
+		assertEquals(50.0, one.bottomAnchor.value)
+		assertEquals(50.0, two.topAnchor.value)
+		assertEquals(125.0, two.bottomAnchor.value)
+		assertEquals(125.0, three.topAnchor.value)
+		assertEquals(175.0, three.bottomAnchor.value)
+
+		assertEquals(175.0, stack.heightAnchor.value)
+	}
+
+	@Test
+	fun testHorizontalLayout() {
+		val stack = view.addSubview(StackView(Axis.HORIZONTAL))
+		val one = stack.addArrangedSubview(View().apply {
+			intrinsicContentSize = Size(50.0, 50.0)
+		})
+		val two = stack.addArrangedSubview(View().apply {
+			intrinsicContentSize = Size(75.0, 75.0)
+		})
+		val three = stack.addArrangedSubview(View().apply {
+			intrinsicContentSize = Size(50.0, 50.0)
+		})
+		window.solver.dsl {
+			stack.leftAnchor equalTo 0
+		}
+		window.layout()
+
+		assertEquals(0.0, abs(one.leftAnchor.value)) // sometimes -0.0, which fails the assertion but is actually ok
+		assertEquals(50.0, one.rightAnchor.value)
+		assertEquals(50.0, two.leftAnchor.value)
+		assertEquals(125.0, two.rightAnchor.value)
+		assertEquals(125.0, three.leftAnchor.value)
+		assertEquals(175.0, three.rightAnchor.value)
+
+		assertEquals(175.0, stack.widthAnchor.value)
+	}
+
+	@Test
+	fun testVerticalLayoutWithLeading() {
+		val stack = view.addSubview(StackView(Axis.VERTICAL, StackView.Distribution.LEADING))
+		val one = stack.addArrangedSubview(View().apply {
+			intrinsicContentSize = Size(50.0, 50.0)
+		})
+		val two = stack.addArrangedSubview(View().apply {
+			intrinsicContentSize = Size(75.0, 75.0)
+		})
+		val three = stack.addArrangedSubview(View().apply {
+			intrinsicContentSize = Size(100.0, 100.0)
+		})
+		window.solver.dsl {
+			stack.topAnchor equalTo 0
+			stack.leftAnchor equalTo 0
+			stack.rightAnchor equalTo 100
+		}
+		window.layout()
+
+		assertEquals(0.0, abs(one.leftAnchor.value))
+		assertEquals(50.0, one.rightAnchor.value)
+
+		assertEquals(0.0, abs(two.leftAnchor.value))
+		assertEquals(75.0, two.rightAnchor.value)
+
+		assertEquals(0.0, abs(three.leftAnchor.value))
+		assertEquals(100.0, three.rightAnchor.value)
+	}
+
+	@Test
+	fun testVerticalLayoutWithTrailing() {
+		val stack = view.addSubview(StackView(Axis.VERTICAL, StackView.Distribution.TRAILING))
+		val one = stack.addArrangedSubview(View().apply {
+			intrinsicContentSize = Size(50.0, 50.0)
+		})
+		val two = stack.addArrangedSubview(View().apply {
+			intrinsicContentSize = Size(75.0, 75.0)
+		})
+		val three = stack.addArrangedSubview(View().apply {
+			intrinsicContentSize = Size(100.0, 100.0)
+		})
+		window.solver.dsl {
+			stack.topAnchor equalTo 0
+			stack.leftAnchor equalTo 0
+			stack.rightAnchor equalTo 100
+		}
+		window.layout()
+
+		assertEquals(50.0, one.leftAnchor.value)
+		assertEquals(100.0, one.rightAnchor.value)
+
+		assertEquals(25.0, two.leftAnchor.value)
+		assertEquals(100.0, two.rightAnchor.value)
+
+		assertEquals(0.0, abs(three.leftAnchor.value))
+		assertEquals(100.0, three.rightAnchor.value)
+	}
+
+	@Test
+	fun testVerticalLayoutWithCenter() {
+		val stack = view.addSubview(StackView(Axis.VERTICAL, StackView.Distribution.CENTER))
+		val one = stack.addArrangedSubview(View().apply {
+			intrinsicContentSize = Size(50.0, 50.0)
+		})
+		val two = stack.addArrangedSubview(View().apply {
+			intrinsicContentSize = Size(75.0, 75.0)
+		})
+		val three = stack.addArrangedSubview(View().apply {
+			intrinsicContentSize = Size(100.0, 100.0)
+		})
+		window.solver.dsl {
+			stack.topAnchor equalTo 0
+			stack.leftAnchor equalTo 0
+			stack.rightAnchor equalTo 100
+		}
+		window.layout()
+
+		assertEquals(25.0, one.leftAnchor.value)
+		assertEquals(75.0, one.rightAnchor.value)
+
+		assertEquals(12.5, two.leftAnchor.value)
+		assertEquals(87.5, two.rightAnchor.value)
+
+		assertEquals(0.0, abs(three.leftAnchor.value))
+		assertEquals(100.0, three.rightAnchor.value)
+	}
+
+	@Test
+	fun testVerticalLayoutWithFill() {
+		val stack = view.addSubview(StackView(Axis.VERTICAL, StackView.Distribution.FILL))
+		val one = stack.addArrangedSubview(View().apply {
+			intrinsicContentSize = Size(50.0, 50.0)
+		})
+		val two = stack.addArrangedSubview(View().apply {
+			intrinsicContentSize = Size(75.0, 75.0)
+		})
+		val three = stack.addArrangedSubview(View().apply {
+			intrinsicContentSize = Size(100.0, 100.0)
+		})
+		window.solver.dsl {
+			stack.topAnchor equalTo 0
+			stack.leftAnchor equalTo 0
+			stack.rightAnchor equalTo 100
+		}
+		window.layout()
+
+		assertEquals(0.0, abs(one.leftAnchor.value))
+		assertEquals(100.0, one.rightAnchor.value)
+
+		assertEquals(0.0, abs(two.leftAnchor.value))
+		assertEquals(100.0, two.rightAnchor.value)
+
+		assertEquals(0.0, abs(three.leftAnchor.value))
+		assertEquals(100.0, three.rightAnchor.value)
+	}
+
+	@Test
+	fun testVerticalLayoutWithSpacing() {
+		val stack = view.addSubview(StackView(Axis.VERTICAL, spacing = 10.0))
+		val one = stack.addArrangedSubview(View().apply {
+			intrinsicContentSize = Size(50.0, 50.0)
+		})
+		val two = stack.addArrangedSubview(View().apply {
+			intrinsicContentSize = Size(75.0, 75.0)
+		})
+		val three = stack.addArrangedSubview(View().apply {
+			intrinsicContentSize = Size(50.0, 50.0)
+		})
+		window.solver.dsl {
+			stack.topAnchor equalTo 0
+		}
+		window.layout()
+
+		assertEquals(0.0, abs(one.topAnchor.value)) // sometimes -0.0, which fails the assertion but is actually ok
+		assertEquals(50.0, one.bottomAnchor.value)
+		assertEquals(60.0, two.topAnchor.value)
+		assertEquals(135.0, two.bottomAnchor.value)
+		assertEquals(145.0, three.topAnchor.value)
+		assertEquals(195.0, three.bottomAnchor.value)
+
+		assertEquals(195.0, stack.heightAnchor.value)
+	}
+
+	@Test
+	fun testHorizontalLayoutWithSpacing() {
+		val stack = view.addSubview(StackView(Axis.HORIZONTAL, spacing = 10.0))
+		val one = stack.addArrangedSubview(View().apply {
+			intrinsicContentSize = Size(50.0, 50.0)
+		})
+		val two = stack.addArrangedSubview(View().apply {
+			intrinsicContentSize = Size(75.0, 75.0)
+		})
+		val three = stack.addArrangedSubview(View().apply {
+			intrinsicContentSize = Size(50.0, 50.0)
+		})
+		window.solver.dsl {
+			stack.leftAnchor equalTo 0
+		}
+		window.layout()
+
+		assertEquals(0.0, abs(one.leftAnchor.value)) // sometimes -0.0, which fails the assertion but is actually ok
+		assertEquals(50.0, one.rightAnchor.value)
+		assertEquals(60.0, two.leftAnchor.value)
+		assertEquals(135.0, two.rightAnchor.value)
+		assertEquals(145.0, three.leftAnchor.value)
+		assertEquals(195.0, three.rightAnchor.value)
+
+		assertEquals(195.0, stack.widthAnchor.value)
+	}
+}

src/test/kotlin/net/shadowfacts/cacao/view/ViewClickTests.kt

@@ -0,0 +1,95 @@
+package net.shadowfacts.cacao.view
+
+import net.shadowfacts.cacao.CacaoScreen
+import net.shadowfacts.cacao.Window
+import net.shadowfacts.cacao.geometry.Point
+import net.shadowfacts.cacao.geometry.Rect
+import net.shadowfacts.cacao.util.MouseButton
+import net.shadowfacts.cacao.viewcontroller.ViewController
+import org.junit.jupiter.api.Assertions.*
+import org.junit.jupiter.api.BeforeEach
+import org.junit.jupiter.api.Test
+import java.util.concurrent.CompletableFuture
+
+/**
+ * @author shadowfacts
+ */
+class ViewClickTests {
+
+	lateinit var screen: CacaoScreen
+	lateinit var window: Window
+	lateinit var viewController: ViewController
+
+	val view: View
+		get() = viewController.view
+
+	@BeforeEach
+	fun setup() {
+		screen = CacaoScreen()
+		viewController = object: ViewController() {
+			override fun loadView() {
+				view = View(Rect(0.0, 0.0, 1000.0, 1000.0))
+			}
+		}
+		window = screen.addWindow(Window(viewController))
+	}
+
+	@Test
+	fun testClickInsideRootView() {
+		val mouse = CompletableFuture<Point>()
+		view.addSubview(object: View(Rect(50.0, 50.0, 100.0, 100.0)) {
+			override fun mouseClicked(point: Point, mouseButton: MouseButton): Boolean {
+				mouse.complete(point)
+				return true
+			}
+		})
+		assertTrue(window.mouseClicked(Point(75.0, 75.0), MouseButton.LEFT))
+
+		assertEquals(Point(25.0, 25.0), mouse.getNow(null))
+	}
+
+	@Test
+	fun testClickOutsideRootView() {
+		val clicked = CompletableFuture<Boolean>()
+		view.addSubview(object: View(Rect(50.0, 50.0, 100.0, 100.0)) {
+			override fun mouseClicked(point: Point, mouseButton: MouseButton): Boolean {
+				clicked.complete(true)
+				return true
+			}
+		})
+		assertFalse(window.mouseClicked(Point(25.0, 25.0), MouseButton.LEFT))
+
+		assertFalse(clicked.getNow(false))
+	}
+
+	@Test
+	fun testClickInsideNestedView() {
+		val mouse = CompletableFuture<Point>()
+		val root = view.addSubview(View(Rect(50.0, 50.0, 100.0, 100.0)))
+		root.addSubview(object: View(Rect(25.0, 25.0, 50.0, 50.0)) {
+			override fun mouseClicked(point: Point, mouseButton: MouseButton): Boolean {
+				mouse.complete(point)
+				return true
+			}
+		})
+		assertTrue(window.mouseClicked(Point(100.0, 100.0), MouseButton.LEFT))
+
+		assertEquals(Point(25.0, 25.0), mouse.getNow(null))
+	}
+
+	@Test
+	fun testClickOutsideNestedView() {
+		val clicked = CompletableFuture<Boolean>()
+		val root = view.addSubview(View(Rect(50.0, 50.0, 100.0, 100.0)))
+		root.addSubview(object: View(Rect(25.0, 25.0, 50.0, 50.0)) {
+			override fun mouseClicked(point: Point, mouseButton: MouseButton): Boolean {
+				clicked.complete(true)
+				return true
+			}
+		})
+		assertFalse(window.mouseClicked(Point(0.0, 0.0), MouseButton.LEFT))
+
+		assertFalse(clicked.getNow(false))
+	}
+
+}

src/test/kotlin/net/shadowfacts/cacao/view/ViewHoverTests.kt

@@ -0,0 +1,73 @@
+package net.shadowfacts.cacao.view
+
+import net.minecraft.client.util.math.MatrixStack
+import net.shadowfacts.cacao.CacaoScreen
+import net.shadowfacts.cacao.Window
+import net.shadowfacts.cacao.geometry.Point
+import net.shadowfacts.cacao.geometry.Rect
+import net.shadowfacts.cacao.viewcontroller.ViewController
+import org.junit.jupiter.api.Assertions.assertEquals
+import org.junit.jupiter.api.BeforeAll
+import org.junit.jupiter.api.BeforeEach
+import org.junit.jupiter.api.Test
+import java.util.concurrent.CompletableFuture
+
+/**
+ * @author shadowfacts
+ */
+class ViewHoverTests {
+
+	lateinit var screen: CacaoScreen
+	lateinit var viewController: ViewController
+	lateinit var window: Window
+	
+	val view: View
+		get() = viewController.view
+
+	companion object {
+		@BeforeAll
+		@JvmStatic
+		fun setupAll() {
+			System.setProperty("cacao.drawing.disabled", "true")
+		}
+	}
+
+	@BeforeEach
+	fun setup() {
+		screen = CacaoScreen()
+		viewController = object: ViewController() {
+			override fun loadView() {
+				view = View(Rect(0.0, 0.0, 1000.0, 1000.0))
+			}
+		}
+		window = screen.addWindow(Window(viewController))
+	}
+
+	@Test
+	fun testHoverRootView() {
+		val point = CompletableFuture<Point>()
+		view.addSubview(object: View(Rect(50.0, 50.0, 100.0, 100.0)) {
+			override fun drawContent(matrixStack: MatrixStack, mouse: Point, delta: Float) {
+				point.complete(mouse)
+			}
+		})
+		window.draw(MatrixStack(), Point(75.0, 75.0), 0f)
+
+		assertEquals(Point(25.0, 25.0), point.getNow(null))
+	}
+
+	@Test
+	fun testHoverNestedView() {
+		val point = CompletableFuture<Point>()
+		val root = view.addSubview(View(Rect(50.0, 50.0, 100.0, 100.0)))
+		root.addSubview(object: View(Rect(25.0, 25.0, 50.0, 50.0)) {
+			override fun drawContent(matrixStack: MatrixStack, mouse: Point, delta: Float) {
+				point.complete(mouse)
+			}
+		})
+		window.draw(MatrixStack(), Point(100.0, 100.0), 0f)
+
+		assertEquals(Point(25.0, 25.0), point.getNow(null))
+	}
+
+}

src/test/kotlin/net/shadowfacts/cacao/view/button/ButtonClickTests.kt

@@ -0,0 +1,83 @@
+package net.shadowfacts.cacao.view.button
+
+import net.shadowfacts.cacao.CacaoScreen
+import net.shadowfacts.cacao.Window
+import net.shadowfacts.cacao.geometry.Point
+import net.shadowfacts.cacao.geometry.Rect
+import net.shadowfacts.cacao.geometry.Size
+import net.shadowfacts.cacao.util.MouseButton
+import net.shadowfacts.cacao.view.View
+import net.shadowfacts.cacao.viewcontroller.ViewController
+import net.shadowfacts.kiwidsl.dsl
+import org.junit.jupiter.api.Assertions.assertFalse
+import org.junit.jupiter.api.Assertions.assertTrue
+import org.junit.jupiter.api.BeforeEach
+import org.junit.jupiter.api.Test
+import java.util.concurrent.CompletableFuture
+
+/**
+ * @author shadowfacts
+ */
+class ButtonClickTests {
+
+	lateinit var screen: CacaoScreen
+	lateinit var window: Window
+	lateinit var viewController: ViewController
+
+	val view: View
+		get() = viewController.view
+
+	@BeforeEach
+	fun setup() {
+		screen = CacaoScreen()
+		viewController = object: ViewController() {
+			override fun loadView() {
+				view = View(Rect(0.0, 0.0, 1000.0, 1000.0))
+			}
+		}
+		window = screen.addWindow(Window(viewController))
+	}
+
+	@Test
+	fun testClickInsideButton() {
+		val clicked = CompletableFuture<Boolean>()
+		val content = View().apply {
+			intrinsicContentSize = Size(25.0, 25.0)
+		}
+		val button = view.addSubview(Button(content).apply {
+			handler = {
+				clicked.complete(true)
+			}
+		})
+		window.solver.dsl {
+			button.leftAnchor equalTo 0
+			button.topAnchor equalTo 0
+		}
+		window.layout()
+
+		assertTrue(window.mouseClicked(Point(5.0, 5.0), MouseButton.LEFT))
+		assertTrue(clicked.getNow(false))
+	}
+
+	@Test
+	fun testClickOutsideButton() {
+		val clicked = CompletableFuture<Boolean>()
+		val content = View().apply {
+			intrinsicContentSize = Size(25.0, 25.0)
+		}
+		val button = view.addSubview(Button(content).apply {
+			handler = {
+				clicked.complete(true)
+			}
+		})
+		window.solver.dsl {
+			button.leftAnchor equalTo 0
+			button.topAnchor equalTo 0
+		}
+		window.layout()
+
+		assertFalse(window.mouseClicked(Point(50.0, 50.0), MouseButton.LEFT))
+		assertFalse(clicked.getNow(false))
+	}
+
+}

src/test/kotlin/net/shadowfacts/cacao/view/button/EnumButtonTests.kt

@@ -0,0 +1,95 @@
+package net.shadowfacts.cacao.view.button
+
+import net.shadowfacts.cacao.CacaoScreen
+import net.shadowfacts.cacao.Window
+import net.shadowfacts.cacao.geometry.Point
+import net.shadowfacts.cacao.geometry.Rect
+import net.shadowfacts.cacao.util.MouseButton
+import net.shadowfacts.cacao.view.View
+import net.shadowfacts.cacao.viewcontroller.ViewController
+import net.shadowfacts.kiwidsl.dsl
+import org.junit.jupiter.api.Assertions.assertEquals
+import org.junit.jupiter.api.Assertions.assertTrue
+import org.junit.jupiter.api.BeforeAll
+import org.junit.jupiter.api.BeforeEach
+import org.junit.jupiter.api.Test
+import java.util.concurrent.CompletableFuture
+
+/**
+ * @author shadowfacts
+ */
+class EnumButtonTests {
+
+	companion object {
+		@BeforeAll
+		@JvmStatic
+		fun setupAll() {
+			System.setProperty("cacao.drawing.disabled", "true")
+		}
+	}
+
+	enum class MyEnum {
+		ONE, TWO, THREE
+	}
+
+	lateinit var screen: CacaoScreen
+	lateinit var window: Window
+	lateinit var viewController: ViewController
+	lateinit var button: EnumButton<MyEnum>
+
+	@BeforeEach
+	fun setup() {
+		screen = CacaoScreen()
+		viewController = object: ViewController() {
+			override fun loadView() {
+				view = View(Rect(0.0, 0.0, 1000.0, 1000.0))
+			}
+		}
+		window = screen.addWindow(Window(viewController))
+		button = viewController.view.addSubview(EnumButton(MyEnum.ONE, MyEnum::name))
+		window.solver.dsl {
+			button.leftAnchor equalTo 0
+			button.topAnchor equalTo 0
+			button.widthAnchor equalTo 25
+			button.heightAnchor equalTo 25
+		}
+		window.layout()
+	}
+
+	@Test
+	fun testHandlerCalled() {
+		val called = CompletableFuture<Boolean>()
+		button.handler = {
+			called.complete(true)
+		}
+
+		assertTrue(window.mouseClicked(Point(5.0, 5.0), MouseButton.LEFT))
+		assertTrue(called.getNow(false))
+		assertEquals(MyEnum.TWO, button.value)
+	}
+
+	@Test
+	fun testCyclesValues() {
+		assertTrue(window.mouseClicked(Point(5.0, 5.0), MouseButton.LEFT))
+		assertEquals(MyEnum.TWO, button.value)
+		assertTrue(window.mouseClicked(Point(5.0, 5.0), MouseButton.LEFT))
+		assertEquals(MyEnum.THREE, button.value)
+		assertTrue(window.mouseClicked(Point(5.0, 5.0), MouseButton.LEFT))
+		assertEquals(MyEnum.ONE, button.value)
+	}
+
+	@Test
+	fun testCyclesValuesBackwards() {
+		assertTrue(window.mouseClicked(Point(5.0, 5.0), MouseButton.LEFT))
+		assertEquals(MyEnum.TWO, button.value)
+		assertTrue(window.mouseClicked(Point(5.0, 5.0), MouseButton.RIGHT))
+		assertEquals(MyEnum.ONE, button.value)
+	}
+
+	@Test
+	fun testMiddleClickDoesNotChangeValue() {
+		assertTrue(window.mouseClicked(Point(5.0, 5.0), MouseButton.MIDDLE))
+		assertEquals(MyEnum.ONE, button.value)
+	}
+
+}

src/test/kotlin/net/shadowfacts/cacao/view/button/ToggleButtonTests.kt

@@ -0,0 +1,86 @@
+package net.shadowfacts.cacao.view.button
+
+import net.shadowfacts.cacao.CacaoScreen
+import net.shadowfacts.cacao.Window
+import net.shadowfacts.cacao.geometry.Point
+import net.shadowfacts.cacao.geometry.Rect
+import net.shadowfacts.cacao.util.MouseButton
+import net.shadowfacts.cacao.view.View
+import net.shadowfacts.cacao.viewcontroller.ViewController
+import org.junit.jupiter.api.Assertions.*
+import org.junit.jupiter.api.BeforeAll
+import org.junit.jupiter.api.BeforeEach
+import org.junit.jupiter.api.Test
+import java.util.concurrent.CompletableFuture
+
+/**
+ * @author shadowfacts
+ */
+class ToggleButtonTests {
+
+	companion object {
+		@BeforeAll
+		@JvmStatic
+		fun setupAll() {
+			System.setProperty("cacao.drawing.disabled", "true")
+		}
+	}
+
+	lateinit var screen: CacaoScreen
+	lateinit var window: Window
+	lateinit var viewController: ViewController
+
+	val view: View
+		get() = viewController.view
+
+	@BeforeEach
+	fun setup() {
+		screen = CacaoScreen()
+		viewController = object: ViewController() {
+			override fun loadView() {
+				view = View(Rect(0.0, 0.0, 1000.0, 1000.0))
+			}
+		}
+		window = screen.addWindow(Window(viewController))
+	}
+
+	@Test
+	fun testHandlerCalled() {
+		val called = CompletableFuture<Boolean>()
+		val button = view.addSubview(ToggleButton(false).apply {
+			frame = Rect(0.0, 0.0, 25.0, 25.0)
+			content.frame = bounds
+			handler = {
+				called.complete(true)
+			}
+		})
+
+		assertTrue(window.mouseClicked(Point(5.0, 5.0), MouseButton.LEFT))
+		assertTrue(called.getNow(false))
+	}
+
+	@Test
+	fun testTogglesValues() {
+		val button = view.addSubview(ToggleButton(false).apply {
+			frame = Rect(0.0, 0.0, 25.0, 25.0)
+			content.frame = bounds
+		})
+
+		assertTrue(window.mouseClicked(Point(5.0, 5.0), MouseButton.LEFT))
+		assertTrue(button.state)
+		assertTrue(window.mouseClicked(Point(5.0, 5.0), MouseButton.LEFT))
+		assertFalse(button.state)
+	}
+
+	@Test
+	fun testMiddleClickDoesNotChangeValue() {
+		val button = view.addSubview(ToggleButton(false).apply {
+			frame = Rect(0.0, 0.0, 25.0, 25.0)
+			content.frame = bounds
+		})
+
+		assertTrue(window.mouseClicked(Point(5.0, 5.0), MouseButton.MIDDLE))
+		assertFalse(button.state)
+	}
+
+}

src/test/kotlin/net/shadowfacts/kiwidsl/DSLTest.kt

@@ -0,0 +1,78 @@
+package net.shadowfacts.kiwidsl
+
+import no.birkett.kiwi.Solver
+import no.birkett.kiwi.Variable
+import org.junit.jupiter.api.Assertions.*
+import org.junit.jupiter.api.BeforeEach
+import org.junit.jupiter.api.Test
+import kotlin.math.abs
+
+/**
+ * @author shadowfacts
+ */
+class DSLTest {
+
+	val EPSILON = 1.0e-8
+
+	lateinit var solver: Solver
+
+	@BeforeEach
+	fun setup() {
+		solver = Solver()
+	}
+
+	@Test
+	fun simpleNew() {
+		val x = Variable("x")
+		solver.dsl {
+			(x + 2) equalTo 20
+		}
+		solver.updateVariables()
+		assertEquals(x.value, 18.0, EPSILON)
+	}
+
+	@Test
+	fun simple0() {
+		val x = Variable("x")
+		val y = Variable("y")
+		solver.dsl {
+			x equalTo 20
+			(x + 2) equalTo (y + 10)
+		}
+		solver.updateVariables()
+		assertEquals(x.value, 20.0, EPSILON)
+		assertEquals(y.value, 12.0, EPSILON)
+	}
+
+	@Test
+	fun simple1() {
+		val x = Variable("x")
+		val y = Variable("y")
+		solver.dsl {
+			x equalTo y
+		}
+		solver.updateVariables()
+		assertEquals(x.value, y.value, EPSILON)
+	}
+
+	@Test
+	fun casso1() {
+		val x = Variable("x")
+		val y = Variable("y")
+		solver.dsl {
+			x lessThanOrEqualTo y
+			y equalTo (x + 3)
+			x.equalTo(10, strength = WEAK)
+			y.equalTo(10, strength = WEAK)
+		}
+		solver.updateVariables()
+		if (abs(x.value - 10.0) < EPSILON) {
+			assertEquals(10.0, x.value, EPSILON)
+			assertEquals(13.0, y.value, EPSILON)
+		} else {
+			assertEquals(7.0, x.value, EPSILON)
+			assertEquals(10.0, y.value, EPSILON)
+		}
+	}
+
+}