Bug 937185 - Discard old apzcs if the ScrollableLayerGuid is updated. r=kats

gfx/layers/composite/APZCTreeManager.cpp

@@ -121,6 +121,14 @@ APZCTreeManager::UpdatePanZoomControllerTree(CompositorParent* aCompositor,
 
         apzc = container->GetAsyncPanZoomController();
 
+        // If the content represented by the container layer has changed (which may
+        // be possible because of DLBI heuristics) then we don't want to keep using
+        // the same old APZC for the new content. Null it out so we run through the
+        // code to find another one or create one.
+        if (apzc && !apzc->Matches(ScrollableLayerGuid(aLayersId, container->GetFrameMetrics()))) {
+          apzc = nullptr;
+        }
+
         // If the container doesn't have an APZC already, try to find one of our
         // pre-existing ones that matches. In particular, if we find an APZC whose
         // ScrollableLayerGuid is the same, then we know what happened is that the
@@ -159,7 +167,7 @@ APZCTreeManager::UpdatePanZoomControllerTree(CompositorParent* aCompositor,
         APZC_LOG("Using APZC %p for layer %p with identifiers %lld %lld\n", apzc, aLayer, aLayersId, container->GetFrameMetrics().mScrollId);
 
         apzc->NotifyLayersUpdated(container->GetFrameMetrics(),
-                                        aIsFirstPaint && (aLayersId == aFirstPaintLayersId));
+                                  aIsFirstPaint && (aLayersId == aFirstPaintLayersId));
 
         ScreenRect visible(container->GetFrameMetrics().mCompositionBounds);
         apzc->SetLayerHitTestData(visible, aTransform, aLayer->GetTransform());

widget/windows/winrt/APZController.cpp

@@ -83,19 +83,22 @@ GetDOMTargets(uint64_t aScrollId,
 class RequestContentRepaintEvent : public nsRunnable
 {
   typedef mozilla::layers::FrameMetrics FrameMetrics;
+  typedef mozilla::layers::ScrollableLayerGuid ScrollableLayerGuid;
 
 public:
   RequestContentRepaintEvent(const FrameMetrics& aFrameMetrics,
                              nsIWidgetListener* aListener,
-                             CSSIntPoint* aLastOffsetOut) :
+                             CSSIntPoint* aLastOffsetOut,
+                             ScrollableLayerGuid* aLastScrollId) :
     mFrameMetrics(aFrameMetrics),
     mWidgetListener(aListener),
-    mLastOffsetOut(aLastOffsetOut)
+    mLastOffsetOut(aLastOffsetOut),
+    mLastScrollIdOut(aLastScrollId)
   {
   }
 
   NS_IMETHOD Run() {
-    // This event shuts down the worker thread and so must be main thread.
+    // This must be on the gecko thread since we access the dom
     MOZ_ASSERT(NS_IsMainThread());
 
 #ifdef DEBUG_CONTROLLER
@@ -139,6 +142,10 @@ public:
         if (mLastOffsetOut) {
           *mLastOffsetOut = actualScrollOffset;
         }
+        if (mLastScrollIdOut) {
+          mLastScrollIdOut->mScrollId = mFrameMetrics.mScrollId;
+          mLastScrollIdOut->mPresShellId = mFrameMetrics.mPresShellId;
+        }
 
 #ifdef DEBUG_CONTROLLER
         WinUtils::Log("APZController: %I64d mDisplayPort: %0.2f %0.2f %0.2f %0.2f",
@@ -156,6 +163,7 @@ protected:
   FrameMetrics mFrameMetrics;
   nsIWidgetListener* mWidgetListener;
   CSSIntPoint* mLastOffsetOut;
+  ScrollableLayerGuid* mLastScrollIdOut;
 };
 
 void
@@ -225,19 +233,19 @@ APZController::ReceiveInputEvent(WidgetInputEvent* aInEvent,
 void
 APZController::RequestContentRepaint(const FrameMetrics& aFrameMetrics)
 {
-  // Send the result back to the main thread so that it can shutdown
   if (!mWidgetListener) {
     NS_WARNING("Can't update display port, !mWidgetListener");
     return;
   }
 
 #ifdef DEBUG_CONTROLLER
-  WinUtils::Log("APZController::RequestContentRepaint scroll id = %I64d",
+  WinUtils::Log("APZController::RequestContentRepaint scrollid=%I64d",
     aFrameMetrics.mScrollId);
 #endif
   nsCOMPtr<nsIRunnable> r1 = new RequestContentRepaintEvent(aFrameMetrics,
                                                             mWidgetListener,
-                                                            &mLastScrollOffset);
+                                                            &mLastScrollOffset,
+                                                            &mLastScrollLayerGuid);
   if (!NS_IsMainThread()) {
     NS_DispatchToMainThread(r1);
   } else {
@@ -253,12 +261,20 @@ APZController::UpdateScrollOffset(const mozilla::layers::ScrollableLayerGuid& aS
                                   CSSIntPoint& aScrollOffset)
 {
 #ifdef DEBUG_CONTROLLER
-  WinUtils::Log("APZController::UpdateScrollOffset: %d %d == %d %d",
+  WinUtils::Log("APZController::UpdateScrollOffset: scrollid:%I64d == %I64d offsets: %d,%d == %d,%d",
+    aScrollLayerId.mScrollId, aScrollLayerId.mScrollId,
     aScrollOffset.x, aScrollOffset.y,
     mLastScrollOffset.x, mLastScrollOffset.y);
 #endif
-  
-  if (!sAPZC || mLastScrollOffset == aScrollOffset) {
+
+  // Bail if this the same scroll guid the apzc just scrolled and the offsets
+  // equal the offset the apzc set.
+  if (!sAPZC || (mLastScrollLayerGuid.mScrollId == aScrollLayerId.mScrollId &&
+                 mLastScrollLayerGuid.mPresShellId == aScrollLayerId.mPresShellId &&
+                 mLastScrollOffset == aScrollOffset)) {
+#ifdef DEBUG_CONTROLLER
+    WinUtils::Log("Skipping UpdateScrollOffset");
+#endif
     return;
   }
   sAPZC->UpdateScrollOffset(aScrollLayerId, aScrollOffset);

widget/windows/winrt/APZController.h

@@ -25,6 +25,11 @@ class APZController :
   typedef mozilla::layers::ScrollableLayerGuid ScrollableLayerGuid;
 
 public:
+  APZController() :
+    mWidgetListener(nullptr)
+  {
+  }
+
   // GeckoContentController interface
   virtual void RequestContentRepaint(const FrameMetrics& aFrameMetrics);
   virtual void HandleDoubleTap(const mozilla::CSSIntPoint& aPoint);
@@ -54,6 +59,7 @@ public:
 
 private:
   nsIWidgetListener* mWidgetListener;
+  ScrollableLayerGuid mLastScrollLayerGuid;
   CSSIntPoint mLastScrollOffset;
 };