CanvasWidget, with example

examples/example1/src/example1.d

@@ -840,6 +840,19 @@ void main()
 
 		tabs.addTab((new SampleAnimationWidget("tab6")).layoutWidth(FILL_PARENT).layoutHeight(FILL_PARENT), "TAB_ANIMATION"c);
 
+		CanvasWidget canvas = new CanvasWidget("canvas");
+		canvas.layoutWidth(FILL_PARENT).layoutHeight(FILL_PARENT);
+		canvas.onDrawListener = delegate(CanvasWidget canvas, DrawBuf buf, Rect rc) {
+			int x = rc.left;
+			int y = rc.top;
+			buf.fillRect(Rect(x+20, y+20, x+150, y+200), 0x80FF80);
+			buf.fillRect(Rect(x+90, y+80, x+250, y+250), 0x80FF80FF);
+			canvas.font.drawText(buf, x + 40, y + 50, "fillRect()"d, 0xC080C0);
+			canvas.font.drawText(buf, x + 300, y + 100, "drawPixel()"d, 0x000080);
+			for (int i = 0; i < 80; i++)
+				buf.drawPixel(x+300 + i * 4, y+140 + i * 3 % 100, 0xFF0000 + i * 2);
+		};
+		tabs.addTab(canvas, "TAB_CANVAS"c);
 
         //==========================================================================
 

examples/example1/views/res/i18n/en.ini

@@ -32,4 +32,5 @@ TAB_BUTTONS=Buttons
 TAB_ANIMATION=Animation
 TAB_TABLE_LAYOUT=Table layout
 TAB_EDITORS=Editors
+TAB_CANVAS=Canvas
 

src/dlangui/widgets/controls.d

@@ -994,3 +994,38 @@ class ScrollBar : AbstractSlider, OnClickHandler {
     }
 }
 
+/// interface - slot for onClick
+interface OnDrawHandler {
+    void doDraw(CanvasWidget canvas, DrawBuf buf, Rect rc);
+}
+
+/// canvas widget - draw on it either by overriding of doDraw() or by assigning of onDrawListener
+class CanvasWidget : Widget {
+	
+	Listener!OnDrawHandler onDrawListener;
+
+    this(string ID = null) {
+		super(ID);
+    }
+
+    override void measure(int parentWidth, int parentHeight) { 
+        measuredContent(parentWidth, parentHeight, 0, 0);
+    }
+
+	void doDraw(DrawBuf buf, Rect rc) {
+		if (onDrawListener.assigned)
+			onDrawListener(this, buf, rc);
+	}
+
+    override void onDraw(DrawBuf buf) {
+        if (visibility != Visibility.Visible)
+            return;
+        super.onDraw(buf);
+        Rect rc = _pos;
+        applyMargins(rc);
+		auto saver = ClipRectSaver(buf, rc, alpha);
+		applyPadding(rc);
+		doDraw(buf, rc);
+    }
+}
+