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Bug 749075. Part 2: Skip the guts of Accumulate if we're adding a display item in an area of the layer that's already opaque and visible. r=mattwoodrow

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This patch moves some stuff that needs to be done for every item up to the front of the function, then checks to
see if the item is being added in an area that's already opaque and visible. If so (and assuming the
color-layer optimization has already been disabled), none of the rest of the method would do anything so we
can exit early. In particular we avoid calling IsUniform and GetOpaqueRegion on the item, and we also avoid
some expensive region manipulation.
This commit is contained in:
Robert O'Callahan 2012-05-03 16:29:05 +12:00
parent 1c1601b380
commit 68cca24d1a
1 changed files with 25 additions and 10 deletions
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35
layout/base/FrameLayerBuilder.cpp
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@ -1192,9 +1192,12 @@ ContainerState::ThebesLayerData::Accumulate(ContainerState* aState,
if (aState->mBuilder->NeedToForceTransparentSurfaceForItem(aItem)) {
mForceTransparentSurface = true;
}
nscolor uniformColor;
bool isUniform = aItem->IsUniform(aState->mBuilder, &uniformColor);
if (aState->mParameters.mDisableSubpixelAntialiasingInDescendants) {
// Disable component alpha.
// Note that the transform (if any) on the ThebesLayer is always an integer translation so
// we don't have to factor that in here.
aItem->DisableComponentAlpha();
}
/* Mark as available for conversion to image layer if this is a nsDisplayImage and
* we are the first visible item in the ThebesLayerData object.
@ -1206,6 +1209,23 @@ ContainerState::ThebesLayerData::Accumulate(ContainerState* aState,
mImage = nsnull;
}
if (!mIsSolidColorInVisibleRegion && mOpaqueRegion.Contains(aDrawRect) &&
mVisibleRegion.Contains(aVisibleRect)) {
// A very common case! Most pages have a ThebesLayer with the page
// background (opaque) visible and most or all of the page content over the
// top of that background.
// The rest of this method won't do anything. mVisibleRegion, mOpaqueRegion
// and mDrawRegion don't need updating. mVisibleRegion contains aVisibleRect
// already, mOpaqueRegion contains aDrawRect and therefore whatever
// the opaque region of the item is. mDrawRegion must contain mOpaqueRegion
// and therefore aDrawRect.
NS_ASSERTION(mDrawRegion.Contains(aDrawRect), "Draw region not covered");
return;
}
nscolor uniformColor;
bool isUniform = aItem->IsUniform(aState->mBuilder, &uniformColor);
// Some display items have to exist (so they can set forceTransparentSurface
// below) but don't draw anything. They'll return true for isUniform but
// a color with opacity 0.
@ -1266,13 +1286,8 @@ ContainerState::ThebesLayerData::Accumulate(ContainerState* aState,
}
}
}
if (aState->mParameters.mDisableSubpixelAntialiasingInDescendants) {
// Disable component alpha. This is cheaper than calling GetComponentAlphaBounds since for
// most items this is a single virtual call that does nothing.
// Note that the transform (if any) on the ThebesLayer is always an integer translation so
// we don't have to factor that in here.
aItem->DisableComponentAlpha();
} else {
if (!aState->mParameters.mDisableSubpixelAntialiasingInDescendants) {
nsRect componentAlpha = aItem->GetComponentAlphaBounds(aState->mBuilder);
if (!componentAlpha.IsEmpty()) {
nsIntRect componentAlphaRect =