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Bug 1055760 - Rearrange AlignFixedAndStickyLayers; no functional changes. r=botond

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This commit is contained in:
Kartikaya Gupta 2014-08-27 22:13:40 -04:00
parent f0b76c5903
commit b997ee23d8
1 changed files with 91 additions and 93 deletions
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184
gfx/layers/composite/AsyncCompositionManager.cpp
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@ -251,108 +251,106 @@ AsyncCompositionManager::AlignFixedAndStickyLayers(Layer* aLayer,
bool isStickyForSubtree = aLayer->GetIsStickyPosition() &&
aLayer->GetStickyScrollContainerId() ==
aTransformedSubtreeRoot->GetFrameMetrics().GetScrollId();
if (aLayer != aTransformedSubtreeRoot && (isRootFixed || isStickyForSubtree)) {
// Insert a translation so that the position of the anchor point is the same
// before and after the change to the transform of aTransformedSubtreeRoot.
// This currently only works for fixed layers with 2D transforms.
bool isFixedOrSticky = (isRootFixed || isStickyForSubtree);
// Accumulate the transforms between this layer and the subtree root layer.
Matrix ancestorTransform;
if (!AccumulateLayerTransforms2D(aLayer->GetParent(), aTransformedSubtreeRoot,
ancestorTransform)) {
return;
// We want to process all the fixed and sticky children of
// aTransformedSubtreeRoot. Also, once we do encounter such a child, we don't
// need to recurse any deeper because the fixed layers are relative to their
// nearest scrollable layer.
if (aLayer == aTransformedSubtreeRoot || !isFixedOrSticky) {
// ApplyAsyncContentTransformToTree will call this function again for
// nested scrollable layers, so we don't need to recurse if the layer is
// scrollable.
if (aLayer == aTransformedSubtreeRoot || !aLayer->GetFrameMetrics().IsScrollable()) {
for (Layer* child = aLayer->GetFirstChild(); child; child = child->GetNextSibling()) {
AlignFixedAndStickyLayers(child, aTransformedSubtreeRoot,
aPreviousTransformForRoot,
aCurrentTransformForRoot, aFixedLayerMargins);
}
}
Matrix oldRootTransform;
Matrix newRootTransform;
if (!aPreviousTransformForRoot.Is2D(&oldRootTransform) ||
!aCurrentTransformForRoot.Is2D(&newRootTransform)) {
return;
}
// Calculate the cumulative transforms between the subtree root with the
// old transform and the current transform.
Matrix oldCumulativeTransform = ancestorTransform * oldRootTransform;
Matrix newCumulativeTransform = ancestorTransform * newRootTransform;
if (newCumulativeTransform.IsSingular()) {
return;
}
Matrix newCumulativeTransformInverse = newCumulativeTransform;
newCumulativeTransformInverse.Invert();
// Now work out the translation necessary to make sure the layer doesn't
// move given the new sub-tree root transform.
Matrix layerTransform;
if (!GetBaseTransform2D(aLayer, &layerTransform)) {
return;
}
// Calculate any offset necessary, in previous transform sub-tree root
// space. This is used to make sure fixed position content respects
// content document fixed position margins.
LayerPoint offsetInOldSubtreeLayerSpace = GetLayerFixedMarginsOffset(aLayer, aFixedLayerMargins);
// Add the above offset to the anchor point so we can offset the layer by
// and amount that's specified in old subtree layer space.
const LayerPoint& anchorInOldSubtreeLayerSpace = aLayer->GetFixedPositionAnchor();
LayerPoint offsetAnchorInOldSubtreeLayerSpace = anchorInOldSubtreeLayerSpace + offsetInOldSubtreeLayerSpace;
// Add the local layer transform to the two points to make the equation
// below this section more convenient.
Point anchor(anchorInOldSubtreeLayerSpace.x, anchorInOldSubtreeLayerSpace.y);
Point offsetAnchor(offsetAnchorInOldSubtreeLayerSpace.x, offsetAnchorInOldSubtreeLayerSpace.y);
Point locallyTransformedAnchor = layerTransform * anchor;
Point locallyTransformedOffsetAnchor = layerTransform * offsetAnchor;
// Transforming the locallyTransformedAnchor by oldCumulativeTransform
// returns the layer's anchor point relative to the parent of
// aTransformedSubtreeRoot, before the new transform was applied.
// Then, applying newCumulativeTransformInverse maps that point relative
// to the layer's parent, which is the same coordinate space as
// locallyTransformedAnchor again, allowing us to subtract them and find
// out the offset necessary to make sure the layer stays stationary.
Point oldAnchorPositionInNewSpace =
newCumulativeTransformInverse * (oldCumulativeTransform * locallyTransformedOffsetAnchor);
Point translation = oldAnchorPositionInNewSpace - locallyTransformedAnchor;
if (aLayer->GetIsStickyPosition()) {
// For sticky positioned layers, the difference between the two rectangles
// defines a pair of translation intervals in each dimension through which
// the layer should not move relative to the scroll container. To
// accomplish this, we limit each dimension of the |translation| to that
// part of it which overlaps those intervals.
const LayerRect& stickyOuter = aLayer->GetStickyScrollRangeOuter();
const LayerRect& stickyInner = aLayer->GetStickyScrollRangeInner();
translation.y = IntervalOverlap(translation.y, stickyOuter.y, stickyOuter.YMost()) -
IntervalOverlap(translation.y, stickyInner.y, stickyInner.YMost());
translation.x = IntervalOverlap(translation.x, stickyOuter.x, stickyOuter.XMost()) -
IntervalOverlap(translation.x, stickyInner.x, stickyInner.XMost());
}
// Finally, apply the 2D translation to the layer transform.
TranslateShadowLayer2D(aLayer, ThebesPoint(translation));
// The transform has now been applied, so there's no need to iterate over
// child layers.
return;
}
// Fixed layers are relative to their nearest scrollable layer, so when we
// encounter a scrollable layer, bail. ApplyAsyncContentTransformToTree will
// have already recursed on this layer and called AlignFixedAndStickyLayers
// on it with its own transforms.
if (aLayer->GetFrameMetrics().IsScrollable() &&
aLayer != aTransformedSubtreeRoot) {
// Insert a translation so that the position of the anchor point is the same
// before and after the change to the transform of aTransformedSubtreeRoot.
// This currently only works for fixed layers with 2D transforms.
// Accumulate the transforms between this layer and the subtree root layer.
Matrix ancestorTransform;
if (!AccumulateLayerTransforms2D(aLayer->GetParent(), aTransformedSubtreeRoot,
ancestorTransform)) {
return;
}
for (Layer* child = aLayer->GetFirstChild();
child; child = child->GetNextSibling()) {
AlignFixedAndStickyLayers(child, aTransformedSubtreeRoot,
aPreviousTransformForRoot,
aCurrentTransformForRoot, aFixedLayerMargins);
Matrix oldRootTransform;
Matrix newRootTransform;
if (!aPreviousTransformForRoot.Is2D(&oldRootTransform) ||
!aCurrentTransformForRoot.Is2D(&newRootTransform)) {
return;
}
// Calculate the cumulative transforms between the subtree root with the
// old transform and the current transform.
Matrix oldCumulativeTransform = ancestorTransform * oldRootTransform;
Matrix newCumulativeTransform = ancestorTransform * newRootTransform;
if (newCumulativeTransform.IsSingular()) {
return;
}
Matrix newCumulativeTransformInverse = newCumulativeTransform;
newCumulativeTransformInverse.Invert();
// Now work out the translation necessary to make sure the layer doesn't
// move given the new sub-tree root transform.
Matrix layerTransform;
if (!GetBaseTransform2D(aLayer, &layerTransform)) {
return;
}
// Calculate any offset necessary, in previous transform sub-tree root
// space. This is used to make sure fixed position content respects
// content document fixed position margins.
LayerPoint offsetInOldSubtreeLayerSpace = GetLayerFixedMarginsOffset(aLayer, aFixedLayerMargins);
// Add the above offset to the anchor point so we can offset the layer by
// and amount that's specified in old subtree layer space.
const LayerPoint& anchorInOldSubtreeLayerSpace = aLayer->GetFixedPositionAnchor();
LayerPoint offsetAnchorInOldSubtreeLayerSpace = anchorInOldSubtreeLayerSpace + offsetInOldSubtreeLayerSpace;
// Add the local layer transform to the two points to make the equation
// below this section more convenient.
Point anchor(anchorInOldSubtreeLayerSpace.x, anchorInOldSubtreeLayerSpace.y);
Point offsetAnchor(offsetAnchorInOldSubtreeLayerSpace.x, offsetAnchorInOldSubtreeLayerSpace.y);
Point locallyTransformedAnchor = layerTransform * anchor;
Point locallyTransformedOffsetAnchor = layerTransform * offsetAnchor;
// Transforming the locallyTransformedAnchor by oldCumulativeTransform
// returns the layer's anchor point relative to the parent of
// aTransformedSubtreeRoot, before the new transform was applied.
// Then, applying newCumulativeTransformInverse maps that point relative
// to the layer's parent, which is the same coordinate space as
// locallyTransformedAnchor again, allowing us to subtract them and find
// out the offset necessary to make sure the layer stays stationary.
Point oldAnchorPositionInNewSpace =
newCumulativeTransformInverse * (oldCumulativeTransform * locallyTransformedOffsetAnchor);
Point translation = oldAnchorPositionInNewSpace - locallyTransformedAnchor;
if (aLayer->GetIsStickyPosition()) {
// For sticky positioned layers, the difference between the two rectangles
// defines a pair of translation intervals in each dimension through which
// the layer should not move relative to the scroll container. To
// accomplish this, we limit each dimension of the |translation| to that
// part of it which overlaps those intervals.
const LayerRect& stickyOuter = aLayer->GetStickyScrollRangeOuter();
const LayerRect& stickyInner = aLayer->GetStickyScrollRangeInner();
translation.y = IntervalOverlap(translation.y, stickyOuter.y, stickyOuter.YMost()) -
IntervalOverlap(translation.y, stickyInner.y, stickyInner.YMost());
translation.x = IntervalOverlap(translation.x, stickyOuter.x, stickyOuter.XMost()) -
IntervalOverlap(translation.x, stickyInner.x, stickyInner.XMost());
}
// Finally, apply the 2D translation to the layer transform.
TranslateShadowLayer2D(aLayer, ThebesPoint(translation));
}
static void