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scenes/opengl: Use hardware clipping for clearing the background

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Right now, when `paintBackground()` is called to clear the background,
we use custom geometry and render that when the damage region isn't
infinite. Rather than using geometry, we can instead use `glScissor()`
to set the area that needs to be cleared and then use `glClear()` to
clear it.

In addition, if we have only one rect in the damage region and that rect
matches the render target rect, we can completely skip all that setup
and use `glClear()` directly.
This commit is contained in:
Arjen Hiemstra 2022-11-24 15:44:47 +01:00 committed by Vlad Zahorodnii
parent f8fb0feab8
commit 63ba8e0eaf
1 changed files with 9 additions and 10 deletions
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19
src/scenes/opengl/scene_opengl.cpp
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@ -92,24 +92,23 @@ void SceneOpenGL::paint(RenderTarget *renderTarget, const QRegion &region)
void SceneOpenGL::paintBackground(const QRegion &region)
{
if (region == infiniteRegion()) {
if (region == infiniteRegion() || (region.rectCount() == 1 && (*region.begin()) == renderTargetRect())) {
glClearColor(0, 0, 0, 0);
glClear(GL_COLOR_BUFFER_BIT);
} else if (!region.isEmpty()) {
QVector<float> verts;
verts.reserve(region.rectCount() * 6 * 2);
glClearColor(0, 0, 0, 0);
glEnable(GL_SCISSOR_TEST);
const auto scale = renderTargetScale();
const auto targetRect = scaledRect(renderTargetRect(), scale).toRect();
for (const QRect &r : region) {
verts << (r.x() + r.width()) * scale << r.y() * scale;
verts << r.x() * scale << r.y() * scale;
verts << r.x() * scale << (r.y() + r.height()) * scale;
verts << r.x() * scale << (r.y() + r.height()) * scale;
verts << (r.x() + r.width()) * scale << (r.y() + r.height()) * scale;
verts << (r.x() + r.width()) * scale << r.y() * scale;
auto deviceRect = scaledRect(r, scale).toAlignedRect();
glScissor(deviceRect.x(), targetRect.height() - (deviceRect.y() + deviceRect.height()), deviceRect.width(), deviceRect.height());
glClear(GL_COLOR_BUFFER_BIT);
}
doPaintBackground(verts);
glDisable(GL_SCISSOR_TEST);
}
}