Bug 1503447 - Remove the clip->ASR == item->ASR hacky code path r=kats
authorDzmitry Malyshau <dmalyshau@mozilla.com>
Sat, 17 Nov 2018 15:44:40 +0000
changeset 446928 aa0c5bc2a99ee57f82ca44da461ebd9870af4275
parent 446927 1bfd0fb3b0d740be0ea913164dce90263aa822d1
child 446929 e432617f70989266c18ffc3cd26a985717fd1bff
push id35058
push usercbrindusan@mozilla.com
push dateSun, 18 Nov 2018 11:14:44 +0000
treeherdermozilla-central@e432617f7098 [default view] [failures only]
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Bug 1503447 - Remove the clip->ASR == item->ASR hacky code path r=kats Previously, WebRender ignored clip_node_id on the clip/scroll stack when pushing clips or reference frames. This got fixed to be more consistent in: https://github.com/servo/webrender/pull/3315 Now Gecko can use the clip chains generated for display items naturally, instead of smuggling the last clip through the scroll_node_id, which is what was happening in this hacky code branch being removed. Differential Revision: https://phabricator.services.mozilla.com/D12216
--- a/gfx/layers/wr/ClipManager.cpp
+++ b/gfx/layers/wr/ClipManager.cpp
@@ -96,17 +96,17 @@ ClipManager::EndList(const StackingConte
 ClipManager::PushOverrideForASR(const ActiveScrolledRoot* aASR,
                                 const wr::WrClipId& aClipId)
   Maybe<wr::WrClipId> scrollId = GetScrollLayer(aASR);
   CLIP_LOG("Pushing override %zu -> %s\n", scrollId->id,
-      Stringify(aClipId->id).c_str());
+      Stringify(aClipId.id).c_str());
   auto it = mASROverride.insert({ *scrollId, std::stack<wr::WrClipId>() });
   // Start a new cache
@@ -117,17 +117,17 @@ ClipManager::PopOverrideForASR(const Act
   Maybe<wr::WrClipId> scrollId = GetScrollLayer(aASR);
   auto it = mASROverride.find(*scrollId);
   MOZ_ASSERT(it != mASROverride.end());
   CLIP_LOG("Popping override %zu -> %s\n", scrollId->id,
-      Stringify(it->second.top()->id).c_str());
+      Stringify(it->second.top().id).c_str());
   if (it->second.empty()) {
 ClipManager::ClipIdAfterOverride(const Maybe<wr::WrClipId>& aClipId)
@@ -136,17 +136,17 @@ ClipManager::ClipIdAfterOverride(const M
     return Nothing();
   auto it = mASROverride.find(*aClipId);
   if (it == mASROverride.end()) {
     return aClipId;
   CLIP_LOG("Overriding %zu with %s\n", aClipId->id,
-      it->second.top() ? Stringify(it->second.top()->id).c_str() : "(none)");
+      Stringify(it->second.top().id).c_str());
   return Some(it->second.top());
 ClipManager::BeginItem(nsDisplayItem* aItem,
                        const StackingContextHelper& aStackingContext)
   CLIP_LOG("processing item %p\n", aItem);
@@ -226,36 +226,17 @@ ClipManager::BeginItem(nsDisplayItem* aI
     leafmostASR = ActiveScrolledRoot::PickDescendant(leafmostASR, clip->mASR);
   Maybe<wr::WrClipId> leafmostId = DefineScrollLayers(leafmostASR, aItem, aStackingContext);
   // Define all the clips in the item's clip chain, and obtain a clip chain id
   // for it.
   clips.mClipChainId = DefineClipChain(clip, auPerDevPixel, aStackingContext);
-  if (clip && clip->mASR == asr) {
-    // If the clip's ASR is the same as the item's ASR, then we want to use
-    // the clip as the "scrollframe" for the item, as WR will do the right thing
-    // when building the ClipScrollTree and ensure the item scrolls with the
-    // ASR. Note in particular that we don't want to use scroll id of |asr| here
-    // because we might have a situation where there is a stacking context
-    // between |asr| and |aItem|, and if we used |asr|'s scroll id, then WR
-    // would effectively hoist the item out of the stacking context and attach
-    // it directly to |asr|. This can produce incorrect results. Using the clip
-    // instead of the ASR is strictly better because the clip is usually defined
-    // inside the stacking context, and so the item also stays "inside" the
-    // stacking context rather than geting hoisted out. Note that there might
-    // be cases where the clip is also "outside" the stacking context and in
-    // theory that situation might not be handled correctly, but I haven't seen
-    // it in practice so far.
-    const ClipIdMap& cache = mCacheStack.top();
-    auto it = cache.find(clip);
-    MOZ_ASSERT(it != cache.end());
-    clips.mScrollId = Some(it->second);
-  } else if (clip) {
+if (clip) {
     // If the clip's ASR is different, then we need to set the scroll id
     // explicitly to match the desired ASR.
     Maybe<wr::WrClipId> scrollId = GetScrollLayer(asr);
     clips.mScrollId = ClipIdAfterOverride(scrollId);
   } else {
     // If we don't have a clip at all, then we don't want to explicitly push
     // the ASR either, because as with the first clause of this if condition,