Bug 958596 - Print ScrollableLayerGuids of APZCs when printing the tree. r=kats

--HG--
extra : rebase_source : cc3688109bb8a8a074e24b2f0268fdc556f05c1f

gfx/layers/FrameMetrics.h

@@ -12,6 +12,7 @@
 #include "mozilla/gfx/BasePoint.h"      // for BasePoint
 #include "mozilla/gfx/Rect.h"           // for RoundedIn
 #include "mozilla/gfx/ScaleFactor.h"    // for ScaleFactor
+#include "mozilla/gfx/Logging.h"        // for Log
 
 namespace IPC {
 template <typename T> struct ParamTraits;
@@ -425,6 +426,11 @@ struct ScrollableLayerGuid {
   }
 };
 
+template <int LogLevel>
+gfx::Log<LogLevel>& operator<<(gfx::Log<LogLevel>& log, const ScrollableLayerGuid& aGuid) {
+  return log << '(' << aGuid.mLayersId << ',' << aGuid.mPresShellId << ',' << aGuid.mScrollId << ')';
+}
+
 struct ZoomConstraints {
   bool mAllowZoom;
   bool mAllowDoubleTapZoom;

gfx/layers/composite/APZCTreeManager.cpp

@@ -170,7 +170,8 @@ APZCTreeManager::UpdatePanZoomControllerTree(CompositorParent* aCompositor,
         // 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()))) {
+        ScrollableLayerGuid guid(aLayersId, container->GetFrameMetrics());
+        if (apzc && !apzc->Matches(guid)) {
           apzc = nullptr;
         }
 
@@ -181,9 +182,8 @@ APZCTreeManager::UpdatePanZoomControllerTree(CompositorParent* aCompositor,
         // underlying content for which the APZC was originally created is still
         // there. So it makes sense to pick up that APZC instance again and use it here.
         if (apzc == nullptr) {
-          ScrollableLayerGuid target(aLayersId, container->GetFrameMetrics());
           for (size_t i = 0; i < aApzcsToDestroy->Length(); i++) {
-            if (aApzcsToDestroy->ElementAt(i)->Matches(target)) {
+            if (aApzcsToDestroy->ElementAt(i)->Matches(guid)) {
               apzc = aApzcsToDestroy->ElementAt(i);
               break;
             }
@@ -234,7 +234,7 @@ APZCTreeManager::UpdatePanZoomControllerTree(CompositorParent* aCompositor,
                                                                               visible.width, visible.height,
                                                                               apzc);
 
-        sApzcTreeLog << "APZC "
+        sApzcTreeLog << "APZC " << guid
                      << "\tcb=" << visible
                      << "\tsr=" << container->GetFrameMetrics().mScrollableRect
                      << "\t" << container->GetFrameMetrics().GetContentDescription();