added LayerdRootElement

src/lib/ui/CanvasStack.hx

@@ -0,0 +1,56 @@
+package lib.ui;
+
+import kernel.ui.Pixel;
+import lib.ui.Canvas;
+
+/**
+	Layer multiple canvases and compress them into one from a top down view.
+**/
+class CanvasStack {
+	private var layers:Array<{c:Canvas, offset:Pos}> = [];
+	private var width:Int = 0;
+	private var hight:Int = 0;
+
+	public function new() {}
+
+	public function addLayer(c:Canvas, offset:Pos) {
+		this.layers.push({c: c, offset: offset});
+
+		var layerWidth = c.maxWidth() + offset.x;
+		var layerHight = c.height() + offset.y;
+
+		if (layerWidth > this.width) {
+			this.width = layerWidth;
+		}
+
+		if (layerHight > this.hight) {
+			this.hight = layerHight;
+		}
+	}
+
+	public function compress():Canvas {
+		var rtn = new Canvas();
+
+		for (y in 0...this.hight) {
+			for (x in 0...this.width) {
+				var pos = new Pos({x: x, y: y});
+				rtn.set(pos, this.pixelAt(pos));
+			}
+		}
+
+		return rtn;
+	}
+
+	public function pixelAt(pos:Pos):Null<Pixel> {
+		for (i in 0...this.layers.length) {
+			var newi = (this.layers.length - 1) - i;
+			var offset = this.layers[newi].offset;
+			var px = this.layers[newi].c.get(pos - offset);
+			if (px != null) {
+				return px;
+			}
+		}
+
+		return null;
+	}
+}

src/lib/ui/elements/LayerdRootElement.hx

@@ -0,0 +1,29 @@
+package lib.ui.elements;
+
+class LayerdRootElement implements UIElement {
+	private var children:Array<{element:UIElement, offset:Pos}>;
+	private final eventManager:UIEventManager = new UIEventManager();
+
+	public function new(?children:Array<{element:UIElement, offset:Pos}>) {
+		this.children = children == null ? [] : children;
+	}
+
+	public function setChildren(children:Array<{element:UIElement, offset:Pos}>) {
+		this.children = children;
+	}
+
+	public function getEventHandlers():UIEvents {
+		return eventManager.getEventHandlers();
+	}
+
+	public function render(bounds:Pos):Canvas {
+		// TODO: add event handle
+		var stack = new CanvasStack();
+
+		for (child in this.children) {
+			stack.addLayer(child.element.render(bounds), child.offset);
+		}
+
+		return stack.compress();
+	}
+}