Add Window constraints

src/main/kotlin/net/shadowfacts/asmr/TestCacaoScreen.kt

@@ -45,9 +45,9 @@ class TestCacaoScreen: CacaoScreen() {
 			})
 
 			solver.dsl {
-				stack.topAnchor equalTo 50
+				stack.topAnchor equalTo 0
-				stack.leftAnchor equalTo 50
+				stack.centerXAnchor equalTo this@apply.centerXAnchor
-				stack.rightAnchor equalTo 150
+				stack.widthAnchor equalTo 100
 				purple.centerXAnchor equalTo blue.centerXAnchor
 				purple.centerYAnchor equalTo blue.centerYAnchor
 //				purple.widthAnchor equalTo 50

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

@@ -1,11 +1,13 @@
 package net.shadowfacts.cacao
 
+import net.minecraft.client.MinecraftClient
 import net.minecraft.client.gui.screen.Screen
 import net.minecraft.network.chat.TextComponent
 import net.minecraft.sound.SoundEvents
 import net.shadowfacts.cacao.geometry.Point
 import net.shadowfacts.cacao.util.MouseButton
 import net.shadowfacts.cacao.util.RenderHelper
+import net.shadowfacts.kiwidsl.dsl
 import java.util.*
 
 /**
@@ -46,6 +48,14 @@ open class CacaoScreen: Screen(TextComponent("CacaoScreen")) {
 		_windows.remove(window)
 	}
 
+	override fun init() {
+		super.init()
+
+		windows.forEach {
+			it.resize(width, height)
+		}
+	}
+
 	override fun render(mouseX: Int, mouseY: Int, delta: Float) {
 		if (minecraft != null) {
 			// workaround this.minecraft sometimes being null causing a crash

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

@@ -3,7 +3,10 @@ package net.shadowfacts.cacao
 import net.shadowfacts.cacao.geometry.Point
 import net.shadowfacts.cacao.util.MouseButton
 import net.shadowfacts.cacao.view.View
+import net.shadowfacts.kiwidsl.dsl
+import no.birkett.kiwi.Constraint
 import no.birkett.kiwi.Solver
+import no.birkett.kiwi.Variable
 import java.util.*
 
 /**
@@ -22,8 +25,49 @@ class Window {
 	 */
 	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
+
 	// _views is the internal, mutable object, since we only want it to be mutated by the add/removeView methods
 	private val _views = LinkedList<View>()
 	/**
@@ -34,6 +78,40 @@ class Window {
 
 	private var viewsSortedByZIndex: List<View> = listOf()
 
+	init {
+		createInternalConstraints()
+	}
+
+	/**
+	 * Creates the internal constraints used by the window.
+	 * If overridden, the super-class method must be called.
+	 */
+	protected open 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].
 	 */

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

@@ -207,7 +207,7 @@ open class View() {
 	 * 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.
 	 */
-	open fun createInternalConstraints() {
+	protected open fun createInternalConstraints() {
 		if (!usesConstraintBasedLayout) return
 
 		solver.dsl {