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Bug 870192 - Prevent rounding issues in gfxMatrix::ScaleFactors from combinging with timing issues to cause sporadic invalidation of transforming elements. r=roc

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This commit is contained in:
Jonathan Watt 2013-05-13 00:12:19 +01:00
parent 98c5262c47
commit eef4016996
1 changed files with 7 additions and 2 deletions
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9
layout/base/FrameLayerBuilder.cpp
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@ -2626,6 +2626,11 @@ ContainerState::Finish(uint32_t* aTextContentFlags, LayerManagerData* aData)
*aTextContentFlags = textContentFlags;
}
static inline gfxSize RoundToFloatPrecision(const gfxSize& aSize)
{
return gfxSize(float(aSize.width), float(aSize.height));
}
static bool
ChooseScaleAndSetTransform(FrameLayerBuilder* aLayerBuilder,
nsDisplayListBuilder* aDisplayListBuilder,
@ -2687,7 +2692,7 @@ ChooseScaleAndSetTransform(FrameLayerBuilder* aLayerBuilder,
scale = nsLayoutUtils::GetMaximumAnimatedScale(aContainerFrame->GetContent());
} else {
//Scale factors are normalized to a power of 2 to reduce the number of resolution changes
scale = transform2d.ScaleFactors(true);
scale = RoundToFloatPrecision(transform2d.ScaleFactors(true));
// For frames with a changing transform that's not just a translation,
// round scale factors up to nearest power-of-2 boundary so that we don't
// keep having to redraw the content as it scales up and down. Rounding up to nearest
@ -2703,7 +2708,7 @@ ChooseScaleAndSetTransform(FrameLayerBuilder* aLayerBuilder,
bool clamp = true;
gfxMatrix oldFrameTransform2d;
if (aLayer->GetBaseTransform().Is2D(&oldFrameTransform2d)) {
gfxSize oldScale = oldFrameTransform2d.ScaleFactors(true);
gfxSize oldScale = RoundToFloatPrecision(oldFrameTransform2d.ScaleFactors(true));
if (oldScale == scale || oldScale == gfxSize(1.0, 1.0)) {
clamp = false;
}