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Bug 584494. Avoid clipping in BasicThebesLayer when not necessary. r=cjones a2.0=blocking2.0:betaN

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This commit is contained in:
Robert O'Callahan
2010-09-17 12:29:52 -07:00
parent 7188004456
commit bc4f762846
2 changed files with 28 additions and 5 deletions
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19
gfx/layers/basic/BasicLayers.cpp
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@@ -492,6 +492,15 @@ BasicThebesLayer::Paint(gfxContext* aContext,
mBuffer.DrawTo(this, canUseOpaqueSurface, target, aOpacity);
}
static PRBool
IsClippingCheap(gfxContext* aTarget, const nsIntRegion& aRegion)
{
// Assume clipping is cheap if the context just has an integer
// translation, and the visible region is simple.
return !aTarget->CurrentMatrix().HasNonIntegerTranslation() &&
aRegion.GetNumRects() <= 1;
}
void
BasicThebesLayerBuffer::DrawTo(ThebesLayer* aLayer,
PRBool aIsOpaqueContent,
@@ -499,7 +508,15 @@ BasicThebesLayerBuffer::DrawTo(ThebesLayer* aLayer,
float aOpacity)
{
aTarget->Save();
gfxUtils::ClipToRegion(aTarget, aLayer->GetVisibleRegion());
// If the entire buffer is valid, we can just draw the whole thing,
// no need to clip. But we'll still clip if clipping is cheap ---
// that might let us copy a smaller region of the buffer.
if (!aLayer->GetValidRegion().Contains(BufferRect()) ||
IsClippingCheap(aTarget, aLayer->GetVisibleRegion())) {
// We don't want to draw invalid stuff, so we need to clip. Might as
// well clip to the smallest area possible --- the visible region.
gfxUtils::ClipToRegion(aTarget, aLayer->GetVisibleRegion());
}
if (aIsOpaqueContent) {
aTarget->SetOperator(gfxContext::OPERATOR_SOURCE);
}