virtual nsIntRegion ComputeChangeInternal(NotifySubDocInvalidationFunc aCallback,
bool& aGeometryChanged)
{
ContainerLayer* container = mLayer->AsContainerLayer();
nsIntRegion result;
bool childrenChanged = false;
if (mPreXScale != container->GetPreXScale() ||
mPreYScale != container->GetPreYScale()) {
aGeometryChanged = true;
result = OldTransformedBounds();
AddRegion(result, NewTransformedBounds());
childrenChanged = true;
// Can't bail out early, we need to update the child container layers
}
// A low frame rate is especially visible to users when scrolling, so we
// particularly want to avoid unnecessary invalidation at that time. For us
// here, that means avoiding unnecessary invalidation of child items when
// other children are added to or removed from our container layer, since
// that may be caused by children being scrolled in or out of view. We are
// less concerned with children changing order.
// TODO: Consider how we could avoid unnecessary invalidation when children
// change order, and whether the overhead would be worth it.
nsDataHashtable<nsPtrHashKey<Layer>, uint32_t> oldIndexMap(mChildren.Length());
for (uint32_t i = 0; i < mChildren.Length(); ++i) {
oldIndexMap.Put(mChildren[i]->mLayer, i);
}
uint32_t i = 0; // cursor into the old child list mChildren
for (Layer* child = container->GetFirstChild(); child; child = child->GetNextSibling()) {
bool invalidateChildsCurrentArea = false;
if (i < mChildren.Length()) {
uint32_t childsOldIndex;
if (oldIndexMap.Get(child, &childsOldIndex)) {
if (childsOldIndex >= i) {
// Invalidate the old areas of layers that used to be between the
// current |child| and the previous |child| that was also in the
// old list mChildren (if any of those children have been reordered
// rather than removed, we will invalidate their new area when we
// encounter them in the new list):
for (uint32_t j = i; j < childsOldIndex; ++j) {
AddRegion(result, mChildren[j]->OldTransformedBounds());
childrenChanged |= true;
}
// Invalidate any regions of the child that have changed:
nsIntRegion region = mChildren[childsOldIndex]->ComputeChange(aCallback, aGeometryChanged);
i = childsOldIndex + 1;
if (!region.IsEmpty()) {
AddRegion(result, region);
childrenChanged |= true;
}
} else {
// We've already seen this child in mChildren (which means it must
// have been reordered) and invalidated its old area. We need to
// invalidate its new area too:
invalidateChildsCurrentArea = true;
}
} else {
// |child| is new
invalidateChildsCurrentArea = true;
}
} else {
// |child| is new, or was reordered to a higher index
invalidateChildsCurrentArea = true;
}
if (invalidateChildsCurrentArea) {
aGeometryChanged = true;
AddTransformedRegion(result, child->GetVisibleRegion(), child->GetLocalTransform());
if (aCallback) {
NotifySubdocumentInvalidationRecursive(child, aCallback);
} else {
ClearInvalidations(child);
}
}
childrenChanged |= invalidateChildsCurrentArea;
}
// Process remaining removed children.
while (i < mChildren.Length()) {
childrenChanged |= true;
AddRegion(result, mChildren[i]->OldTransformedBounds());
i++;
}
if (aCallback) {
aCallback(container, result);
}
if (childrenChanged) {
container->SetChildrenChanged(true);
}
result.Transform(gfx::To3DMatrix(mLayer->GetLocalTransform()));
return result;
}
