Bug 1494408 - Clip groups to the transform clip to avoid bounds changes. r=jrmuizel

Differential Revision: https://phabricator.services.mozilla.com/D17983

--HG--
extra : moz-landing-system : lando

gfx/layers/wr/WebRenderCommandBuilder.cpp

@@ -1301,6 +1301,15 @@ void WebRenderCommandBuilder::DoGroupingForDisplayList(
 
   bool snapped;
   nsRect groupBounds = aWrappingItem->GetBounds(aDisplayListBuilder, &snapped);
+  // We don't want to restrict the size of the blob to the building rect of the
+  // display item, since that will change when we scroll and trigger a resize
+  // invalidation of the blob (will be fixed by blob recoordination).
+  // Instead we retrieve the bounds of the overflow clip on the <svg> and use
+  // that to restrict our size and prevent invisible content from affecting
+  // our bounds.
+  if (mClippedGroupBounds) {
+    groupBounds = groupBounds.Intersect(mClippedGroupBounds.value());
+  }
   DIGroup& group = groupData->mSubGroup;
 
   gfx::Size scale = aSc.GetInheritedScale();
@@ -1485,7 +1494,8 @@ bool WebRenderCommandBuilder::ShouldDumpDisplayList(
 void WebRenderCommandBuilder::CreateWebRenderCommandsFromDisplayList(
     nsDisplayList* aDisplayList, nsDisplayItem* aWrappingItem,
     nsDisplayListBuilder* aDisplayListBuilder, const StackingContextHelper& aSc,
-    wr::DisplayListBuilder& aBuilder, wr::IpcResourceUpdateQueue& aResources) {
+    wr::DisplayListBuilder& aBuilder, wr::IpcResourceUpdateQueue& aResources,
+    nsDisplayItem* aOuterItem) {
   if (mDoGrouping) {
     MOZ_RELEASE_ASSERT(
         aWrappingItem,
@@ -1595,6 +1605,25 @@ void WebRenderCommandBuilder::CreateWebRenderCommandsFromDisplayList(
         // animated geometry root, so we can combine subsequent items of that
         // type into the same image.
         mContainsSVGGroup = mDoGrouping = true;
+        if (aOuterItem &&
+            aOuterItem->GetType() == DisplayItemType::TYPE_TRANSFORM) {
+          // Inline <svg> should always have an overflow clip, but it gets put
+          // outside the nsDisplayTransform we create for scaling the svg
+          // viewport. Converting the clip into inner coordinates lets us
+          // restrict the size of the blob images and prevents unnecessary
+          // resizes.
+          nsDisplayTransform* transform =
+              static_cast<nsDisplayTransform*>(aOuterItem);
+
+          nsRect clippedBounds =
+              transform->GetClippedBounds(aDisplayListBuilder);
+          nsRect innerClippedBounds;
+          DebugOnly<bool> result = transform->UntransformRect(
+              aDisplayListBuilder, clippedBounds, &innerClippedBounds);
+          MOZ_ASSERT(result);
+
+          mClippedGroupBounds = Some(innerClippedBounds);
+        }
         GP("attempting to enter the grouping code\n");
       }
 

gfx/layers/wr/WebRenderCommandBuilder.h

@@ -92,10 +92,11 @@ class WebRenderCommandBuilder {
                        nsDisplayListBuilder* aDisplayListBuilder);
 
   void CreateWebRenderCommandsFromDisplayList(
-      nsDisplayList* aDisplayList, nsDisplayItem* aOuterItem,
+      nsDisplayList* aDisplayList, nsDisplayItem* aWrappingItem,
       nsDisplayListBuilder* aDisplayListBuilder,
       const StackingContextHelper& aSc, wr::DisplayListBuilder& aBuilder,
-      wr::IpcResourceUpdateQueue& aResources);
+      wr::IpcResourceUpdateQueue& aResources,
+      nsDisplayItem* aOuterItem = nullptr);
 
   // aWrappingItem has to be non-null.
   void DoGroupingForDisplayList(nsDisplayList* aDisplayList,
@@ -201,6 +202,7 @@ class WebRenderCommandBuilder {
   // Whether consecutive inactive display items should be grouped into one
   // blob image.
   bool mDoGrouping;
+  Maybe<nsRect> mClippedGroupBounds;
 
   // True if we're currently within an opacity:0 container, and only
   // plugin and hit test items should be considered.

layout/painting/nsDisplayList.cpp

@@ -7893,8 +7893,10 @@ bool nsDisplayTransform::CreateWebRenderCommands(
                            params,
                            LayoutDeviceRect(position, LayoutDeviceSize()));
 
-  return mStoredList.CreateWebRenderCommands(aBuilder, aResources, sc, aManager,
-                                             aDisplayListBuilder);
+  aManager->CommandBuilder().CreateWebRenderCommandsFromDisplayList(
+      mStoredList.GetChildren(), &mStoredList, aDisplayListBuilder, sc,
+      aBuilder, aResources, this);
+  return true;
 }
 
 bool nsDisplayTransform::UpdateScrollData(