Add Z index and view sorting

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

@@ -26,6 +26,8 @@ class Window {
 	 */
 	val views: List<View> = _views
 
+	private var viewsSortedByZIndex: List<View> = listOf()
+
 	/**
 	 * Adds the given view as a top-level view in this window.
 	 *
@@ -34,6 +36,9 @@ class Window {
 	 */
 	fun <T: View> addView(view: T): T {
 		_views.add(view)
+		viewsSortedByZIndex = views.sortedBy(View::zIndex)
+
+		view.window = this
 		view.solver = solver
 
 		view.wasAdded()
@@ -42,11 +47,22 @@ class Window {
 	}
 
 	/**
-	 * Attempts to find a top level view of this window that contains the given point.
+	 * Finds all views in this window at the given point.
-	 * If there are multiple overlapping views, which one this method returns is undefined.
 	 *
 	 * @param point The point to find views at, in the coordinate system of the window.
-	 * @return The view, if any, that contains the given point.
+	 * @return All views that contain the point.
+	 */
+	fun viewsAtPoint(point: Point): List<View> {
+		return views.filter { point in it.frame }
+	}
+
+	/**
+	 * Attempts to find a top level view of this window that contains the given point.
+	 * If there are multiple overlapping views, which one this method returns is undefined.
+	 * [viewsAtPoint] may be used, and the resulting List sorted by [View.zIndex].
+	 *
+	 * @param point The point to find views at, in the coordinate system of the window.
+	 * @return the Veiw, if any, that contain the given point.
 	 */
 	fun viewAtPoint(point: Point): View? {
 		return views.firstOrNull { point in it.frame }
@@ -69,7 +85,7 @@ class Window {
 	 * @param delta The time elapsed since the last frame.
 	 */
 	fun draw(mouse: Point, delta: Float) {
-		views.forEach {
+		viewsSortedByZIndex.forEach {
 			val mouseInView = Point(mouse.x - it.frame.left, mouse.y - it.frame.top)
 			it.draw(mouseInView, delta)
 		}
@@ -84,7 +100,7 @@ class Window {
 	 * @return Whether the mouse click was handled by a view.
 	 */
 	fun mouseClicked(point: Point, mouseButton: MouseButton): Boolean {
-		val view = viewAtPoint(point)
+		val view = viewsAtPoint(point).minBy(View::zIndex)
 		if (view != null) {
 			val pointInView = Point(point.x - view.frame.left, point.y - view.frame.top)
 			return view.mouseClicked(pointInView, mouseButton)

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

@@ -78,6 +78,12 @@ open class View() {
 	 */
 	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.
@@ -104,6 +110,9 @@ open class View() {
 	var superview: View? = null
 	// _subviews is the internal, mutable object since we only want it to by 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.
@@ -143,6 +152,8 @@ open class View() {
 	 */
 	fun <T: View> addSubview(view: T): T {
 		_subviews.add(view)
+		subviewsSortedByZIndex = subviews.sortedBy(View::zIndex)
+
 		view.superview = this
 		view.solver = solver
 
@@ -151,9 +162,20 @@ open class View() {
 		return view
 	}
 
+	/**
+	 * 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.
@@ -233,7 +255,7 @@ open class View() {
 
 		drawContent(mouse, delta)
 
-		subviews.forEach {
+		subviewsSortedByZIndex.forEach {
 			val mouseInView = convert(mouse, to = it)
 			it.draw(mouseInView, delta)
 		}
@@ -261,7 +283,7 @@ open class View() {
 	 * @return Whether the mouse click was handled by this view or any subviews.
 	 */
 	open fun mouseClicked(point: Point, mouseButton: MouseButton): Boolean {
-		val view = subviewAtPoint(point)
+		val view = subviewsAtPoint(point).maxBy(View::zIndex)
 		if (view != null) {
 			val pointInView = convert(point, to = view)
 			return view.mouseClicked(pointInView, mouseButton)