Bug 1027380 - Paint flashing from an inactive layer manager saturates the transparent layers. r=mattwoodrow

--HG--
extra : rebase_source : 7444cf86fc14bd811d836d4c788958bf3790f572

gfx/layers/Layers.h

@@ -213,6 +213,7 @@ public:
    * and is used for drawing into the widget.
    */
   virtual bool IsWidgetLayerManager() { return true; }
+  virtual bool IsInactiveLayerManager() { return false; }
 
   /**
    * Start a new transaction. Nested transactions are not allowed so

gfx/layers/basic/BasicLayerManager.cpp

@@ -210,10 +210,12 @@ public:
   bool mPushedOpaqueRect;
 };
 
-BasicLayerManager::BasicLayerManager(nsIWidget* aWidget) :
-  mPhase(PHASE_NONE),
-  mWidget(aWidget)
-  , mDoubleBuffering(BufferMode::BUFFER_NONE), mUsingDefaultTarget(false)
+BasicLayerManager::BasicLayerManager(nsIWidget* aWidget)
+  : mPhase(PHASE_NONE)
+  , mWidget(aWidget)
+  , mDoubleBuffering(BufferMode::BUFFER_NONE)
+  , mType(BLM_WIDGET)
+  , mUsingDefaultTarget(false)
   , mTransactionIncomplete(false)
   , mCompositorMightResample(false)
 {
@@ -221,13 +223,16 @@ BasicLayerManager::BasicLayerManager(nsIWidget* aWidget) :
   NS_ASSERTION(aWidget, "Must provide a widget");
 }
 
-BasicLayerManager::BasicLayerManager() :
-  mPhase(PHASE_NONE),
-  mWidget(nullptr)
-  , mDoubleBuffering(BufferMode::BUFFER_NONE), mUsingDefaultTarget(false)
+BasicLayerManager::BasicLayerManager(BasicLayerManagerType aType)
+  : mPhase(PHASE_NONE)
+  , mWidget(nullptr)
+  , mDoubleBuffering(BufferMode::BUFFER_NONE)
+  , mType(aType)
+  , mUsingDefaultTarget(false)
   , mTransactionIncomplete(false)
 {
   MOZ_COUNT_CTOR(BasicLayerManager);
+  MOZ_ASSERT(mType != BLM_WIDGET);
 }
 
 BasicLayerManager::~BasicLayerManager()

gfx/layers/basic/BasicLayers.h

@@ -45,13 +45,18 @@ class BasicLayerManager :
     public LayerManager
 {
 public:
+  enum BasicLayerManagerType {
+    BLM_WIDGET,
+    BLM_OFFSCREEN,
+    BLM_INACTIVE
+  };
   /**
    * Construct a BasicLayerManager which will have no default
    * target context. SetDefaultTarget or BeginTransactionWithTarget
    * must be called for any rendering to happen. ThebesLayers will not
    * be retained.
    */
-  BasicLayerManager();
+  BasicLayerManager(BasicLayerManagerType aType);
   /**
    * Construct a BasicLayerManager which will have no default
    * target context. SetDefaultTarget or BeginTransactionWithTarget
@@ -89,6 +94,7 @@ public:
   void ClearRetainerWidget() { mWidget = nullptr; }
 
   virtual bool IsWidgetLayerManager() { return mWidget != nullptr; }
+  virtual bool IsInactiveLayerManager() { return mType == BLM_INACTIVE; }
 
   virtual void BeginTransaction();
   virtual void BeginTransactionWithTarget(gfxContext* aTarget);
@@ -183,6 +189,7 @@ protected:
   nsRefPtr<ImageFactory> mFactory;
 
   BufferMode mDoubleBuffering;
+  BasicLayerManagerType mType;
   bool mUsingDefaultTarget;
   bool mTransactionIncomplete;
   bool mCompositorMightResample;

layout/base/FrameLayerBuilder.cpp

@@ -2826,7 +2826,7 @@ FrameLayerBuilder::AddThebesDisplayItem(ThebesLayerData* aLayerData,
       tempManager = data->mInactiveManager;
     }
     if (!tempManager) {
-      tempManager = new BasicLayerManager();
+      tempManager = new BasicLayerManager(BasicLayerManager::BLM_INACTIVE);
     }
 
     // We need to grab these before calling AddLayerDisplayItem because it will overwrite them.
@@ -3891,7 +3891,8 @@ FrameLayerBuilder::DrawThebesLayer(ThebesLayer* aLayer,
                              entry->mCommonClipCount);
   }
 
-  if (presContext->GetPaintFlashing()) {
+  if (presContext->GetPaintFlashing() &&
+      !aLayer->Manager()->IsInactiveLayerManager()) {
     gfxContextAutoSaveRestore save(aContext);
     if (shouldDrawRectsSeparately) {
       if (aClip == DrawRegionClip::DRAW_SNAPPED) {

layout/base/nsDisplayList.cpp

@@ -1280,7 +1280,7 @@ void nsDisplayList::PaintForFrame(nsDisplayListBuilder* aBuilder,
       NS_WARNING("Nowhere to paint into");
       return;
     }
-    layerManager = new BasicLayerManager();
+    layerManager = new BasicLayerManager(BasicLayerManager::BLM_OFFSCREEN);
   }
 
   // Store the existing layer builder to reinstate it on return.