Provide some simple OpenGL primitives.

CMakeLists.txt

@@ -63,6 +63,8 @@ PRIVATE
     ui/gl/gl_image.h
     ui/gl/gl_math.cpp
     ui/gl/gl_math.h
+    ui/gl/gl_primitives.cpp
+    ui/gl/gl_primitives.h
     ui/gl/gl_shader.cpp
     ui/gl/gl_shader.h
     ui/gl/gl_surface.cpp

ui/gl/gl_math.cpp

@@ -32,4 +32,13 @@ QSizeF Uniform(QSize size) {
 	return size;
 }
 
+Rect TransformRect(const Rect &raster, QSize viewport, float factor) {
+	return {
+		raster.left() * factor,
+		float(viewport.height() - raster.bottom()) * factor,
+		raster.width() * factor,
+		raster.height() * factor,
+	};
+}
+
 } // namespace Ui::GL

ui/gl/gl_math.h

@@ -76,4 +76,9 @@ private:
 [[nodiscard]] QVector4D Uniform(const QColor &color);
 [[nodiscard]] QSizeF Uniform(QSize size);
 
+[[nodiscard]] Rect TransformRect(
+	const Rect &raster,
+	QSize viewport,
+	float factor);
+
 } // namespace Ui::GL

ui/gl/gl_primitives.cpp

@@ -0,0 +1,148 @@
+// This file is part of Desktop App Toolkit,
+// a set of libraries for developing nice desktop applications.
+//
+// For license and copyright information please follow this link:
+// https://github.com/desktop-app/legal/blob/master/LEGAL
+//
+#include "ui/gl/gl_primitives.h"
+
+#include "ui/gl/gl_shader.h"
+#include "ui/style/style_core.h"
+
+#include <QtGui/QOpenGLFunctions>
+
+namespace Ui::GL {
+
+static_assert(std::is_same_v<float, GLfloat>);
+
+void FillRectVertices(float *coords, Rect rect) {
+	coords[0] = coords[10] = rect.left();
+	coords[1] = coords[11] = rect.top();
+	coords[2] = rect.right();
+	coords[3] = rect.top();
+	coords[4] = coords[6] = rect.right();
+	coords[5] = coords[7] = rect.bottom();
+	coords[8] = rect.left();
+	coords[9] = rect.bottom();
+}
+
+void FillTriangles(
+		QOpenGLFunctions &f,
+		gsl::span<const float> coords,
+		not_null<QOpenGLBuffer*> buffer,
+		not_null<QOpenGLShaderProgram*> program,
+		QSize viewportWithFactor,
+		const QColor &color,
+		Fn<void()> additional) {
+	Expects(coords.size() % 6 == 0);
+
+	if (coords.empty()) {
+		return;
+	}
+	buffer->bind();
+	buffer->allocate(coords.data(), coords.size() * sizeof(GLfloat));
+
+	f.glUseProgram(program->programId());
+	program->setUniformValue("viewport", QSizeF(viewportWithFactor));
+	program->setUniformValue("s_color", Uniform(color));
+
+	GLint position = program->attributeLocation("position");
+	f.glVertexAttribPointer(
+		position,
+		2,
+		GL_FLOAT,
+		GL_FALSE,
+		2 * sizeof(GLfloat),
+		nullptr);
+	f.glEnableVertexAttribArray(position);
+
+	if (additional) {
+		additional();
+	}
+
+	f.glDrawArrays(GL_TRIANGLES, 0, coords.size() / 2);
+
+	f.glDisableVertexAttribArray(position);
+}
+
+void FillTexturedRectangle(
+		QOpenGLFunctions &f,
+		not_null<QOpenGLShaderProgram*> program,
+		int skipVertices) {
+	const auto shift = [&](int elements) {
+		return reinterpret_cast<const void*>(
+			(skipVertices * 4 + elements) * sizeof(GLfloat));
+	};
+	GLint position = program->attributeLocation("position");
+	f.glVertexAttribPointer(
+		position,
+		2,
+		GL_FLOAT,
+		GL_FALSE,
+		4 * sizeof(GLfloat),
+		shift(0));
+	f.glEnableVertexAttribArray(position);
+
+	GLint texcoord = program->attributeLocation("v_texcoordIn");
+	f.glVertexAttribPointer(
+		texcoord,
+		2,
+		GL_FLOAT,
+		GL_FALSE,
+		4 * sizeof(GLfloat),
+		shift(2));
+	f.glEnableVertexAttribArray(texcoord);
+
+	f.glDrawArrays(GL_TRIANGLE_FAN, 0, 4);
+
+	f.glDisableVertexAttribArray(position);
+	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 style::color &color) {
+	const auto &rgb = color->c.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) {
+		FillRectVertices(coords, TransformRect(rect, viewport, factor));
+		coords += 12;
+	}
+	FillTriangles(
+		f,
+		_bgTriangles,
+		&*_bgBuffer,
+		&*_bgProgram,
+		viewport * factor,
+		rgb);
+}
+
+} // namespace Ui::GL

ui/gl/gl_primitives.h

@@ -0,0 +1,54 @@
+// This file is part of Desktop App Toolkit,
+// a set of libraries for developing nice desktop applications.
+//
+// For license and copyright information please follow this link:
+// https://github.com/desktop-app/legal/blob/master/LEGAL
+//
+#pragma once
+
+#include "ui/gl/gl_math.h"
+#include "ui/style/style_core.h"
+
+#include <QtGui/QOpenGLBuffer>
+#include <QtGui/QOpenGLShaderProgram>
+
+class QOpenGLFunctions;
+
+namespace Ui::GL {
+
+void FillRectVertices(float *coords, Rect rect);
+
+void FillTriangles(
+	QOpenGLFunctions &f,
+	gsl::span<const float> coords,
+	not_null<QOpenGLBuffer*> buffer,
+	not_null<QOpenGLShaderProgram*> program,
+	QSize viewportWithFactor,
+	const QColor &color,
+	Fn<void()> additional = nullptr);
+
+void FillTexturedRectangle(
+	QOpenGLFunctions &f,
+	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 style::color &color);
+
+private:
+	std::optional<QOpenGLBuffer> _bgBuffer;
+	std::optional<QOpenGLShaderProgram> _bgProgram;
+	std::vector<float> _bgTriangles;
+
+};
+
+} // namespace Ui::GL

ui/style/style_core.cpp

@@ -126,18 +126,19 @@ void colorizeImage(const QImage &src, QColor c, QImage *outResult, QRect srcRect
 	outResult->setDevicePixelRatio(src.devicePixelRatio());
 }
 
-QBrush transparentPlaceholderBrush() {
+QImage TransparentPlaceholder() {
-	auto size = st::transparentPlaceholderSize * DevicePixelRatio();
+	const auto size = st::transparentPlaceholderSize * DevicePixelRatio();
-	auto transparent = QImage(2 * size, 2 * size, QImage::Format_ARGB32_Premultiplied);
+	auto result = QImage(
-	transparent.fill(st::mediaviewTransparentBg->c);
+		2 * size, 2 * size,
+		QImage::Format_ARGB32_Premultiplied);
+	result.fill(st::mediaviewTransparentBg->c);
 	{
-		QPainter p(&transparent);
+		QPainter p(&result);
 		p.fillRect(0, size, size, size, st::mediaviewTransparentFg);
 		p.fillRect(size, 0, size, size, st::mediaviewTransparentFg);
 	}
-	transparent.setDevicePixelRatio(DevicePixelRatio());
+	result.setDevicePixelRatio(DevicePixelRatio());
-	return QBrush(transparent);
+	return result;
-
 }
 
 namespace internal {

ui/style/style_core.h

@@ -58,7 +58,7 @@ inline QImage colorizeImage(const QImage &src, const color &c, QRect srcRect = Q
 	return colorizeImage(src, c->c, srcRect);
 }
 
-QBrush transparentPlaceholderBrush();
+[[nodiscard]] QImage TransparentPlaceholder();
 
 namespace internal {