Remove BackgroundFiller, use glClear in paintEvent.

ui/gl/gl_primitives.cpp

@@ -122,53 +122,4 @@ void FillTexturedRectangle(
 	f.glDisableVertexAttribArray(texcoord);
 }
 
-void BackgroundFiller::init(QOpenGLFunctions &f) {
-	_bgBuffer.emplace();
-	_bgBuffer->setUsagePattern(QOpenGLBuffer::DynamicDraw);
-	_bgBuffer->create();
-	_bgProgram.emplace();
-	LinkProgram(
-		&*_bgProgram,
-		VertexShader({ VertexViewportTransform() }),
-		FragmentShader({ FragmentStaticColor() }));
-}
-
-void BackgroundFiller::deinit(QOpenGLFunctions &f) {
-	_bgProgram.reset();
-	_bgBuffer.reset();
-}
-
-void BackgroundFiller::fill(
-		QOpenGLFunctions &f,
-		const QRegion &region,
-		QSize viewport,
-		float factor,
-		const QColor &color) {
-	const auto rgb = color.toRgb();
-	if (region.isEmpty()) {
-		return;
-	} else if (region.end() - region.begin() == 1
-		&& (*region.begin()).size() == viewport) {
-		f.glClearColor(rgb.redF(), rgb.greenF(), rgb.blueF(), rgb.alphaF());
-		f.glClear(GL_COLOR_BUFFER_BIT);
-		return;
-	}
-	_bgTriangles.resize((region.end() - region.begin()) * 12);
-	auto coords = _bgTriangles.data();
-	for (const auto rect : region) {
-		FillRectTriangleVertices(
-			coords,
-			TransformRect(rect, viewport, factor));
-		coords += 12;
-	}
-	_bgProgram->bind();
-	_bgProgram->setUniformValue("viewport", QSizeF(viewport * factor));
-	FillTriangles(
-		f,
-		_bgTriangles,
-		&*_bgBuffer,
-		&*_bgProgram,
-		rgb);
-}
-
 } // namespace Ui::GL

ui/gl/gl_primitives.h

@@ -37,32 +37,4 @@ void FillTexturedRectangle(
 	not_null<QOpenGLShaderProgram*> program,
 	int skipVertices = 0);
 
-class BackgroundFiller final {
-public:
-	void init(QOpenGLFunctions &f);
-	void deinit(QOpenGLFunctions &);
-
-	void fill(
-		QOpenGLFunctions &f,
-		const QRegion &region,
-		QSize viewport,
-		float factor,
-		const QColor &color);
-
-	void fill(
-			QOpenGLFunctions &f,
-			const QRegion &region,
-			QSize viewport,
-			float factor,
-			const style::color &color) {
-		return fill(f, region, viewport, factor, color->c);
-	}
-
-private:
-	std::optional<QOpenGLBuffer> _bgBuffer;
-	std::optional<QOpenGLShaderProgram> _bgProgram;
-	std::vector<float> _bgTriangles;
-
-};
-
 } // namespace Ui::GL

ui/gl/gl_surface.cpp

@@ -30,7 +30,7 @@ public:
 private:
 	void initializeGL() override;
 	void resizeGL(int w, int h) override;
-	void paintGL() override;
+	void paintEvent(QPaintEvent *e) override;
 	void callDeInit();
 
 	const std::unique_ptr<Renderer> _renderer;
@@ -78,8 +78,22 @@ void SurfaceOpenGL::resizeGL(int w, int h) {
 	_renderer->resize(this, *context()->functions(), w, h);
 }
 
-void SurfaceOpenGL::paintGL() {
-	_renderer->paint(this, *context()->functions());
+void SurfaceOpenGL::paintEvent(QPaintEvent *e) {
+	if (!updatesEnabled() || size().isEmpty() || !isValid()) {
+		return;
+	}
+	makeCurrent();
+	const auto f = context()->functions();
+	if (const auto bg = _renderer->clearColor()) {
+		f->glClearColor(bg->redF(), bg->greenF(), bg->blueF(), bg->alphaF());
+		f->glClear(GL_COLOR_BUFFER_BIT);
+	}
+	f->glViewport(
+		0,
+		0,
+		width() * devicePixelRatio(),
+		height() * devicePixelRatio());
+	_renderer->paint(this, *f);
 }
 
 void SurfaceOpenGL::callDeInit() {

ui/gl/gl_surface.h

@@ -42,6 +42,10 @@ public:
         not_null<QOpenGLWidget*> widget,
         QOpenGLFunctions &f);
 
+	[[nodiscard]] virtual std::optional<QColor> clearColor() {
+		return std::nullopt;
+	}
+
     virtual void paintFallback(
         Painter &&p,
         const QRegion &clip,