Allow containerless scrolling for root scroll frames, too. (bug 1076192, r=tn)

--HG--
extra : rebase_source : 29d74a8734aabc0e583ad5e372f7b04bcc9e2b8f

dom/base/nsDOMWindowUtils.cpp

@@ -375,7 +375,7 @@ nsDOMWindowUtils::SetDisplayPortForElement(float aXPx, float aYPx,
                        new DisplayPortPropertyData(displayport, aPriority),
                        nsINode::DeleteProperty<DisplayPortPropertyData>);
 
-  if (nsLayoutUtils::UsesAsyncScrolling()) {
+  if (nsLayoutUtils::UsesAsyncScrolling() && gfxPrefs::LayoutUseContainersForRootFrames()) {
     nsIFrame* rootScrollFrame = presShell->GetRootScrollFrame();
     if (rootScrollFrame && content == rootScrollFrame->GetContent()) {
       // We are setting a root displayport for a document.

gfx/thebes/gfxPrefs.h

@@ -330,6 +330,9 @@ private:
 
   DECL_GFX_PREF(Once, "dom.vr.enabled",                        VREnabled, bool, false);
   DECL_GFX_PREF(Once, "dom.vr.add-test-devices",               VRAddTestDevices, int32_t, 1);
+
+  // This and code dependent on it should be removed once containerless scrolling looks stable.
+  DECL_GFX_PREF(Once, "layout.scroll.root-frame-containers",   LayoutUseContainersForRootFrames, bool, true);
 public:
   // Manage the singleton:
   static gfxPrefs& GetSingleton()

layout/base/FrameLayerBuilder.cpp

@@ -3034,9 +3034,11 @@ ContainerState::ProcessDisplayItems(nsDisplayList* aList)
             scrollItem->IsDisplayPortOpaque();
         newLayerEntry->mBaseFrameMetrics =
             scrollItem->ComputeFrameMetrics(ownLayer, mParameters);
-      } else if (itemType == nsDisplayItem::TYPE_SUBDOCUMENT ||
-                 itemType == nsDisplayItem::TYPE_ZOOM ||
-                 itemType == nsDisplayItem::TYPE_RESOLUTION) {
+      } else if ((itemType == nsDisplayItem::TYPE_SUBDOCUMENT ||
+                  itemType == nsDisplayItem::TYPE_ZOOM ||
+                  itemType == nsDisplayItem::TYPE_RESOLUTION) &&
+                 gfxPrefs::LayoutUseContainersForRootFrames())
+      {
         newLayerEntry->mBaseFrameMetrics =
           static_cast<nsDisplaySubDocument*>(item)->ComputeFrameMetrics(ownLayer, mParameters);
       }

layout/base/nsDisplayList.cpp

@@ -1503,23 +1503,25 @@ already_AddRefed<LayerManager> nsDisplayList::PaintRoot(nsDisplayListBuilder* aB
   root->SetPostScale(1.0f/containerParameters.mXScale,
                      1.0f/containerParameters.mYScale);
 
-  bool isRoot = presContext->IsRootContentDocument();
+  if (gfxPrefs::LayoutUseContainersForRootFrames()) {
+    bool isRoot = presContext->IsRootContentDocument();
 
-  nsIFrame* rootScrollFrame = presShell->GetRootScrollFrame();
+    nsIFrame* rootScrollFrame = presShell->GetRootScrollFrame();
 
-  nsRect viewport(aBuilder->ToReferenceFrame(frame), frame->GetSize());
+    nsRect viewport(aBuilder->ToReferenceFrame(frame), frame->GetSize());
 
-  root->SetFrameMetrics(
-    nsDisplayScrollLayer::ComputeFrameMetrics(frame, rootScrollFrame,
-                       aBuilder->FindReferenceFrameFor(frame),
-                       root, FrameMetrics::NULL_SCROLL_ID, viewport,
-                       !isRoot, isRoot, containerParameters));
+    root->SetFrameMetrics(
+      nsDisplayScrollLayer::ComputeFrameMetrics(frame, rootScrollFrame,
+                         aBuilder->FindReferenceFrameFor(frame),
+                         root, FrameMetrics::NULL_SCROLL_ID, viewport,
+                         !isRoot, isRoot, containerParameters));
+  }
 
   // NS_WARNING is debug-only, so don't even bother checking the conditions in
   // a release build.
 #ifdef DEBUG
   bool usingDisplayport = false;
-  if (rootScrollFrame) {
+  if (nsIFrame* rootScrollFrame = presShell->GetRootScrollFrame()) {
     nsIContent* content = rootScrollFrame->GetContent();
     if (content) {
       usingDisplayport = nsLayoutUtils::GetDisplayPort(content, nullptr);

layout/base/nsLayoutUtils.cpp

@@ -1014,7 +1014,7 @@ nsLayoutUtils::SetDisplayPortMargins(nsIContent* aContent,
                             aMargins, aPriority),
                         nsINode::DeleteProperty<DisplayPortMarginsPropertyData>);
 
-  if (nsLayoutUtils::UsesAsyncScrolling()) {
+  if (nsLayoutUtils::UsesAsyncScrolling() && gfxPrefs::LayoutUseContainersForRootFrames()) {
     nsIFrame* rootScrollFrame = aPresShell->GetRootScrollFrame();
     if (rootScrollFrame && aContent == rootScrollFrame->GetContent()) {
       // We are setting a root displayport for a document.

layout/generic/nsGfxScrollFrame.cpp

@@ -2847,6 +2847,8 @@ ScrollFrameHelper::BuildDisplayList(nsDisplayListBuilder*   aBuilder,
     mOuter->PresContext()->IsRootContentDocument();
 
   if (aBuilder->GetIgnoreScrollFrame() == mOuter || IsIgnoringViewportClipping()) {
+    // Root scrollframes have FrameMetrics and clipping on their container
+    // layers, so don't apply clipping again.
     mAddClipRectToLayer = false;
 
     // If we are a root scroll frame that has a display port we want to add
@@ -2877,6 +2879,8 @@ ScrollFrameHelper::BuildDisplayList(nsDisplayListBuilder*   aBuilder,
     return;
   }
 
+  // Root scrollframes have FrameMetrics and clipping on their container
+  // layers, so don't apply clipping again.
   mAddClipRectToLayer =
     !(mIsRoot && mOuter->PresContext()->PresShell()->GetIsViewportOverridden());
 
@@ -2895,7 +2899,23 @@ ScrollFrameHelper::BuildDisplayList(nsDisplayListBuilder*   aBuilder,
   if (aBuilder->IsPaintingToWindow()) {
     bool wasUsingDisplayPort = nsLayoutUtils::GetDisplayPort(mOuter->GetContent(), nullptr);
 
-    if (!mIsRoot) {
+    if (mIsRoot) {
+      if (gfxPrefs::LayoutUseContainersForRootFrames()) {
+        // For a root frame in a container, just get the value of the existing
+        // display port if any.
+        usingDisplayport = nsLayoutUtils::GetDisplayPort(mOuter->GetContent(), &displayPort);
+      } else {
+        // Override the value of the display port base rect, and possibly create a
+        // display port if there isn't one already.
+        nsRect displayportBase = dirtyRect;
+        if (mIsRoot && mOuter->PresContext()->IsRootContentDocument()) {
+          displayportBase =
+            nsRect(nsPoint(0, 0), nsLayoutUtils::CalculateCompositionSizeForFrame(mOuter));
+        }
+        usingDisplayport = nsLayoutUtils::GetOrMaybeCreateDisplayPort(
+              *aBuilder, mOuter, displayportBase, &displayPort);
+      }
+    } else {
       // For a non-root scroll frame, override the value of the display port
       // base rect, and possibly create a display port if there isn't one
       // already. For root scroll frame, nsLayoutUtils::PaintFrame or
@@ -2903,10 +2923,6 @@ ScrollFrameHelper::BuildDisplayList(nsDisplayListBuilder*   aBuilder,
       nsRect displayportBase = dirtyRect;
       usingDisplayport = nsLayoutUtils::GetOrMaybeCreateDisplayPort(
           *aBuilder, mOuter, displayportBase, &displayPort);
-    } else {
-      // For a root frame, just get the value of the existing display port, if
-      // any.
-      usingDisplayport = nsLayoutUtils::GetDisplayPort(mOuter->GetContent(), &displayPort);
     }
 
     bool usingLowPrecision = gfxPrefs::UseLowPrecisionBuffer();
@@ -2968,10 +2984,12 @@ ScrollFrameHelper::BuildDisplayList(nsDisplayListBuilder*   aBuilder,
     shouldBuildLayer =
       nsLayoutUtils::WantSubAPZC() &&
       WantAsyncScroll() &&
-      // If we are the root scroll frame for the display root then we don't need a scroll
-      // info layer to make a ComputeFrameMetrics call for us as
-      // nsDisplayList::PaintForFrame already calls ComputeFrameMetrics for us.
-      (!mIsRoot || aBuilder->RootReferenceFrame()->PresContext() != mOuter->PresContext());
+      // If we are using containers for root frames, and we are the root
+      // scroll frame for the display root, then we don't need a scroll
+      // info layer. nsDisplayList::PaintForFrame already calls
+      // ComputeFrameMetrics for us.
+      (!(gfxPrefs::LayoutUseContainersForRootFrames() && mIsRoot) ||
+       (aBuilder->RootReferenceFrame()->PresContext() != mOuter->PresContext()));
   }
 
   if (aBuilder->IsPaintingToWindow() &&
@@ -3119,8 +3137,6 @@ ScrollFrameHelper::ComputeFrameMetrics(Layer* aLayer,
 {
   nsRect scrollport = mScrollPort +
     mOuter->GetOffsetToCrossDoc(aContainerReferenceFrame);
-  // Root scrollframes have FrameMetrics and clipping on their container layers,
-  // so don't also apply clipping here.
   if (mAddClipRectToLayer) {
     *aClipRect = scrollport;
   }
@@ -3131,10 +3147,12 @@ ScrollFrameHelper::ComputeFrameMetrics(Layer* aLayer,
 
   MOZ_ASSERT(mScrolledFrame->GetContent());
 
+  bool isRoot = mIsRoot && mOuter->PresContext()->IsRootContentDocument();
+
   *aOutput->AppendElement() =
       nsDisplayScrollLayer::ComputeFrameMetrics(mScrolledFrame, mOuter,
         aContainerReferenceFrame, aLayer, mScrollParentID,
-        scrollport, false, false, aParameters);
+        scrollport, false, isRoot, aParameters);
 }
 
 bool

layout/generic/nsGfxScrollFrame.h

@@ -450,6 +450,7 @@ public:
   // If true, the layer should always be active because we always build a
   // scrollable layer. Used for asynchronous scrolling.
   bool mShouldBuildScrollableLayer:1;
+
   // If true, add clipping in ScrollFrameHelper::ComputeFrameMetrics.
   bool mAddClipRectToLayer:1;
 

layout/generic/nsSubDocumentFrame.cpp

@@ -413,16 +413,18 @@ nsSubDocumentFrame::BuildDisplayList(nsDisplayListBuilder*   aBuilder,
     dirty = dirty.ConvertAppUnitsRoundOut(parentAPD, subdocAPD);
 
     if (nsIFrame* rootScrollFrame = presShell->GetRootScrollFrame()) {
-      // for root content documents we want the base to be the composition bounds
-      nsRect displayportBase = presContext->IsRootContentDocument() ?
-          nsRect(nsPoint(0,0), nsLayoutUtils::CalculateCompositionSizeForFrame(rootScrollFrame)) :
-          dirty.Intersect(nsRect(nsPoint(0,0), subdocRootFrame->GetSize()));
-      nsRect displayPort;
-      if (aBuilder->IsPaintingToWindow() &&
-          nsLayoutUtils::GetOrMaybeCreateDisplayPort(
-            *aBuilder, rootScrollFrame, displayportBase, &displayPort)) {
-        haveDisplayPort = true;
-        dirty = displayPort;
+      if (gfxPrefs::LayoutUseContainersForRootFrames()) {
+        // for root content documents we want the base to be the composition bounds
+        nsRect displayportBase = presContext->IsRootContentDocument() ?
+            nsRect(nsPoint(0,0), nsLayoutUtils::CalculateCompositionSizeForFrame(rootScrollFrame)) :
+            dirty.Intersect(nsRect(nsPoint(0,0), subdocRootFrame->GetSize()));
+        nsRect displayPort;
+        if (aBuilder->IsPaintingToWindow() &&
+            nsLayoutUtils::GetOrMaybeCreateDisplayPort(
+              *aBuilder, rootScrollFrame, displayportBase, &displayPort)) {
+          haveDisplayPort = true;
+          dirty = displayPort;
+        }
       }
 
       ignoreViewportScrolling = presShell->IgnoringViewportScrolling();
@@ -453,9 +455,15 @@ nsSubDocumentFrame::BuildDisplayList(nsDisplayListBuilder*   aBuilder,
   bool constructResolutionItem = subdocRootFrame &&
     (presShell->GetXResolution() != 1.0 || presShell->GetYResolution() != 1.0);
   bool constructZoomItem = subdocRootFrame && parentAPD != subdocAPD;
-  bool needsOwnLayer = constructResolutionItem || constructZoomItem ||
-    haveDisplayPort ||
-    presContext->IsRootContentDocument() || (sf && sf->IsScrollingActive(aBuilder));
+  bool needsOwnLayer = false;
+  if (constructResolutionItem ||
+      constructZoomItem ||
+      haveDisplayPort ||
+      presContext->IsRootContentDocument() ||
+      (sf && sf->IsScrollingActive(aBuilder)))
+  {
+    needsOwnLayer = true;
+  }
 
   nsDisplayList childItems;