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Bug 1645433 - Avoid using INT32_MAX as the z-index of inactive scrollframe items. r=mattwoodrow

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Differential Revision: https://phabricator.services.mozilla.com/D97063
This commit is contained in:
Botond Ballo 2020-11-20 01:18:24 +00:00
parent 2151575956
commit 94bd7fb7c9
1 changed files with 45 additions and 1 deletions
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46
layout/generic/nsGfxScrollFrame.cpp
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@ -3528,6 +3528,26 @@ class MOZ_RAII AutoContainsBlendModeCapturer {
}
};
// Finds the max z-index of the items in aList that meet the following
// conditions
// 1) have z-index auto or z-index >= 0.
// 2) aFrame is a proper ancestor of the item's frame.
// Returns -1 if there is no such item.
static int32_t MaxZIndexInListOfItemsContainedInFrame(nsDisplayList* aList,
nsIFrame* aFrame) {
int32_t maxZIndex = -1;
for (nsDisplayItem* item = aList->GetBottom(); item;
item = item->GetAbove()) {
nsIFrame* itemFrame = item->Frame();
// Perspective items return the scroll frame as their Frame(), so consider
// their TransformFrame() instead.
if (nsLayoutUtils::IsProperAncestorFrame(aFrame, itemFrame)) {
maxZIndex = std::max(maxZIndex, item->ZIndex());
}
}
return maxZIndex;
}
void ScrollFrameHelper::BuildDisplayList(nsDisplayListBuilder* aBuilder,
const nsDisplayListSet& aLists) {
SetAndNullOnExit<const nsIFrame> tmpBuilder(
@ -4046,11 +4066,35 @@ void ScrollFrameHelper::BuildDisplayList(nsDisplayListBuilder* aBuilder,
// create a displayport for this frame. We'll add the item later on.
if (!mWillBuildScrollableLayer) {
if (aBuilder->BuildCompositorHitTestInfo()) {
int32_t zIndex = MaxZIndexInListOfItemsContainedInFrame(
scrolledContent.PositionedDescendants(), mOuter);
if (aBuilder->IsPartialUpdate()) {
if (auto* items =
mScrolledFrame->GetProperty(nsIFrame::DisplayItems())) {
for (nsDisplayItemBase* item : *items) {
if (item->GetType() ==
DisplayItemType::TYPE_COMPOSITOR_HITTEST_INFO) {
auto* hitTestItem =
static_cast<nsDisplayCompositorHitTestInfo*>(item);
if (hitTestItem->HasHitTestInfo() &&
hitTestItem->HitTestFlags().contains(
CompositorHitTestFlags::eInactiveScrollframe)) {
zIndex = std::max(zIndex, hitTestItem->ZIndex());
item->SetCantBeReused();
}
}
}
}
}
// Make sure the z-index of the inactive item is at least zero.
// Otherwise, it will end up behind non-positioned items in the scrolled
// content.
zIndex = std::max(zIndex, 0);
nsDisplayCompositorHitTestInfo* hitInfo =
MakeDisplayItemWithIndex<nsDisplayCompositorHitTestInfo>(
aBuilder, mScrolledFrame, 1, info, Some(area));
if (hitInfo) {
AppendInternalItemToTop(scrolledContent, hitInfo, Some(INT32_MAX));
AppendInternalItemToTop(scrolledContent, hitInfo, Some(zIndex));
}
}
}