Custom OpenGL drawable

examples/example1/src/example1.d

@@ -894,6 +894,11 @@ void main()
 		};
 		tabs.addTab(canvas, "TAB_CANVAS"c);
 
+		static if (ENABLE_OPENGL) {
+			//
+			tabs.addTab(new MyOpenglWidget(), "OpenGL"d);
+		}
+
         //==========================================================================
 
         contentLayout.addChild(tabs);
@@ -914,3 +919,19 @@ void main()
 
     return Platform.instance.enterMessageLoop();
 }
+
+static if (ENABLE_OPENGL) {
+	class MyOpenglWidget : Widget {
+		this() {
+			super("OpenGLView");
+			layoutWidth = FILL_PARENT;
+			layoutHeight = FILL_PARENT;
+			backgroundDrawable = DrawableRef(new OpenGLDrawable(&doDraw));
+		}
+
+		private void doDraw(DrawBuf buf, Rect rc) {
+			// do some drawing
+			// TODO
+		}
+	}
+}

src/dlangui/graphics/drawbuf.d

@@ -39,6 +39,9 @@ static if (ENABLE_OPENGL) {
     private __gshared uint drawBufIdGenerator = 0;
 }
 
+/// Custom draw delegate for OpenGL direct drawing
+alias OpenGLDrawableDelegate = void delegate(DrawBuf buf, Rect rc);
+
 /// drawing buffer - image container which allows to perform some drawing operations
 class DrawBuf : RefCountedObject {
     protected Rect _clipRect;
@@ -384,6 +387,12 @@ class DrawBuf : RefCountedObject {
         return this;
     }
 
+	/// draw custom OpenGL scene
+	void drawCustomOpenGLScene(Rect rc, OpenGLDrawableDelegate handler) {
+		// override it for OpenGL draw buffer
+		Log.w("drawCustomOpenGLScene is called for non-OpenGL DrawBuf");
+	}
+
     void clear() {
 		resetClipping();
     }

src/dlangui/graphics/gldrawbuf.d

@@ -89,6 +89,11 @@ class GLDrawBuf : DrawBuf, GLConfigCallback {
         resetClipping();
     }
 
+	/// draw custom OpenGL scene
+	override void drawCustomOpenGLScene(Rect rc, OpenGLDrawableDelegate handler) {
+		_scene.add(new CustomDrawnSceneItem(this, rc, handler));
+	}
+
     /// fill the whole buffer with solid color (no clipping applied)
     override void fill(uint color) {
         if (hasClipping) {
@@ -905,3 +910,25 @@ public:
 	~this() {
 	}
 }
+
+private class CustomDrawnSceneItem : SceneItem {
+private:
+	DrawBuf _buf;
+	Rect _rc;
+	OpenGLDrawableDelegate _handler;
+public:
+	this(DrawBuf buf, Rect rc, OpenGLDrawableDelegate handler) {
+		_buf = buf;
+		_rc = rc;
+		_handler = handler;
+	}
+	override void draw() {
+		if (_handler) {
+			import derelict.opengl3.gl3;
+			import derelict.opengl3.gl;
+			glViewport(_rc.left, _rc.top, _rc.right, _rc.bottom);
+			_handler(_buf, _rc);
+			glSupport.setOrthoProjection(Rect(0, 0, _buf.width, _buf.height));
+		}
+	}
+}

src/dlangui/graphics/resources.d

@@ -221,6 +221,7 @@ immutable(ubyte[]) loadResourceBytes(string filename) {
     }
 }
 
+/// Base class for all drawables
 class Drawable : RefCountedObject {
 	debug static __gshared int _instanceCount;
 	debug @property static int instanceCount() { return _instanceCount; }
@@ -239,6 +240,37 @@ class Drawable : RefCountedObject {
     @property Rect padding() { return Rect(0,0,0,0); }
 }
 
+/// Custom drawing inside openGL
+class OpenGLDrawable : Drawable {
+	
+	private OpenGLDrawableDelegate _drawHandler;
+
+	@property OpenGLDrawableDelegate drawHandler() { return _drawHandler; }
+	@property OpenGLDrawable drawHandler(OpenGLDrawableDelegate handler) { _drawHandler = handler; return this; }
+
+	this(OpenGLDrawableDelegate drawHandler = null) {
+		_drawHandler = drawHandler;
+	}
+
+	void onDraw(DrawBuf buf, Rect rc) {
+		// either override this method or assign draw handler
+		if (_drawHandler) {
+			_drawHandler(buf, rc);
+		}
+	}
+
+    override void drawTo(DrawBuf buf, Rect rc, uint state = 0, int tilex0 = 0, int tiley0 = 0) {
+		buf.drawCustomOpenGLScene(rc, &onDraw);
+	}
+
+    override @property int width() {
+		return 20; // dummy size
+	}
+    override @property int height() {
+		return 20; // dummy size
+	}
+}
+
 class EmptyDrawable : Drawable {
     override void drawTo(DrawBuf buf, Rect rc, uint state = 0, int tilex0 = 0, int tiley0 = 0) {
     }

src/dlangui/widgets/widget.d

@@ -402,9 +402,16 @@ class Widget {
         return style.focusRectColors;
     }
 
+	DrawableRef _backgroundDrawable;
 	/// background drawable
 	@property DrawableRef backgroundDrawable() const {
+		if (_backgroundDrawable.isNull)
 			return stateStyle.backgroundDrawable;
+		return (cast(Widget)this)._backgroundDrawable;
+	}
+	/// background drawable
+	@property void backgroundDrawable(DrawableRef drawable) {
+		_backgroundDrawable = drawable;
 	}
 
 	/// widget drawing alpha value (0=opaque .. 255=transparent)