Bug 922942 - Add a Validate() pass to BasicLayers to avoid needing to create a dummy destination context. r=roc

gfx/layers/basic/BasicContainerLayer.cpp

@@ -115,6 +115,20 @@ BasicContainerLayer::ChildrenPartitionVisibleRegion(const nsIntRect& aInRect)
   return covered.Contains(rect);
 }
 
+void
+BasicContainerLayer::Validate(LayerManager::DrawThebesLayerCallback aCallback,
+                              void* aCallbackData)
+{
+  for (Layer* l = mFirstChild; l; l = l->GetNextSibling()) {
+    BasicImplData* data = ToData(l);
+    data->Validate(aCallback, aCallbackData);
+    if (l->GetMaskLayer()) {
+      data = ToData(l->GetMaskLayer());
+      data->Validate(aCallback, aCallbackData);
+    }
+  }
+}
+
 already_AddRefed<ContainerLayer>
 BasicLayerManager::CreateContainerLayer()
 {

gfx/layers/basic/BasicContainerLayer.h

@@ -76,6 +76,9 @@ public:
 
   void SetSupportsComponentAlphaChildren(bool aSupports) { mSupportsComponentAlphaChildren = aSupports; }
 
+  virtual void Validate(LayerManager::DrawThebesLayerCallback aCallback,
+                        void* aCallbackData) MOZ_OVERRIDE;
+
 protected:
   BasicLayerManager* BasicManager()
   {

gfx/layers/basic/BasicImplData.h

@@ -73,6 +73,9 @@ public:
                            void* aCallbackData,
                            ReadbackProcessor* aReadback) {}
 
+  virtual void Validate(LayerManager::DrawThebesLayerCallback aCallback,
+                        void* aCallbackData) {}
+
   /**
    * Layers will get this call when their layer manager is destroyed, this
    * indicates they should clear resources they don't really need after their

gfx/layers/basic/BasicLayerManager.cpp

@@ -581,22 +581,32 @@ BasicLayerManager::EndTransactionInternal(DrawThebesLayerCallback aCallback,
   NS_ASSERTION(InConstruction(), "Should be in construction phase");
   mPhase = PHASE_DRAWING;
 
-  Layer* aLayer = GetRoot();
-  RenderTraceLayers(aLayer, "FF00");
+  RenderTraceLayers(mRoot, "FF00");
 
   mTransactionIncomplete = false;
 
-  if (aFlags & END_NO_COMPOSITE) {
-    if (!mDummyTarget) {
-      // XXX: We should really just set mTarget to null and make sure we can handle that further down the call chain
-      // Creating this temporary surface can be expensive on some platforms (d2d in particular), so cache it between paints.
-      nsRefPtr<gfxASurface> surf = gfxPlatform::GetPlatform()->CreateOffscreenSurface(gfxIntSize(1, 1), GFX_CONTENT_COLOR);
-      mDummyTarget = new gfxContext(surf);
+  if (mRoot) {
+    // Need to do this before we call ApplyDoubleBuffering,
+    // which depends on correct effective transforms
+    mSnapEffectiveTransforms =
+      mTarget ? !(mTarget->GetFlags() & gfxContext::FLAG_DISABLE_SNAPPING) : true;
+    mRoot->ComputeEffectiveTransforms(mTarget ? gfx3DMatrix::From2D(mTarget->CurrentMatrix()) : gfx3DMatrix());
+
+    ToData(mRoot)->Validate(aCallback, aCallbackData);
+    if (mRoot->GetMaskLayer()) {
+      ToData(mRoot->GetMaskLayer())->Validate(aCallback, aCallbackData);
+    }
+
+    if (aFlags & END_NO_COMPOSITE) {
+      // Apply pending tree updates before recomputing effective
+      // properties.
+      mRoot->ApplyPendingUpdatesToSubtree();
     }
-    mTarget = mDummyTarget;
   }
 
-  if (mTarget && mRoot && !(aFlags & END_NO_IMMEDIATE_REDRAW)) {
+  if (mTarget && mRoot &&
+      !(aFlags & END_NO_IMMEDIATE_REDRAW) &&
+      !(aFlags & END_NO_COMPOSITE)) {
     nsIntRect clipRect;
 
     {
@@ -605,18 +615,6 @@ BasicLayerManager::EndTransactionInternal(DrawThebesLayerCallback aCallback,
       clipRect = ToOutsideIntRect(mTarget->GetClipExtents());
     }
 
-    if (aFlags & END_NO_COMPOSITE) {
-      // Apply pending tree updates before recomputing effective
-      // properties.
-      aLayer->ApplyPendingUpdatesToSubtree();
-    }
-
-    // Need to do this before we call ApplyDoubleBuffering,
-    // which depends on correct effective transforms
-    mSnapEffectiveTransforms =
-      !(mTarget->GetFlags() & gfxContext::FLAG_DISABLE_SNAPPING);
-    mRoot->ComputeEffectiveTransforms(gfx3DMatrix::From2D(mTarget->CurrentMatrix()));
-
     if (IsRetained()) {
       nsIntRegion region;
       MarkLayersHidden(mRoot, clipRect, clipRect, region, ALLOW_OPAQUE);
@@ -625,22 +623,12 @@ BasicLayerManager::EndTransactionInternal(DrawThebesLayerCallback aCallback,
       }
     }
 
-    if (aFlags & END_NO_COMPOSITE) {
-      if (IsRetained()) {
-        // Clip the destination out so that we don't draw to it, and
-        // only end up validating ThebesLayers.
-        mTarget->Clip(gfxRect(0, 0, 0, 0));
-        PaintLayer(mTarget, mRoot, aCallback, aCallbackData, nullptr);
-      }
-      // If we're not retained, then don't composite means do nothing at all.
-    } else {
-      PaintLayer(mTarget, mRoot, aCallback, aCallbackData, nullptr);
-      if (mWidget) {
-        FlashWidgetUpdateArea(mTarget);
-      }
-      RenderDebugOverlay();
-      LayerManager::PostPresent();
+    PaintLayer(mTarget, mRoot, aCallback, aCallbackData, nullptr);
+    if (mWidget) {
+      FlashWidgetUpdateArea(mTarget);
     }
+    RenderDebugOverlay();
+    LayerManager::PostPresent();
 
     if (!mTransactionIncomplete) {
       // Clear out target if we have a complete transaction.

gfx/layers/basic/BasicLayers.h

@@ -186,7 +186,6 @@ protected:
   nsRefPtr<gfxContext> mDefaultTarget;
   // The context to draw into.
   nsRefPtr<gfxContext> mTarget;
-  nsRefPtr<gfxContext> mDummyTarget;
   // Image factory we use.
   nsRefPtr<ImageFactory> mFactory;
 

gfx/layers/basic/BasicThebesLayer.cpp

@@ -90,21 +90,11 @@ BasicThebesLayer::PaintThebes(gfxContext* aContext,
   NS_ASSERTION(BasicManager()->InDrawing(),
                "Can only draw in drawing phase");
 
-  if (!mContentClient) {
-    // we pass a null pointer for the Forwarder argument, which means
-    // this will not have a ContentHost on the other side.
-    mContentClient = new ContentClientBasic(nullptr, BasicManager());
-  }
-
   nsTArray<ReadbackProcessor::Update> readbackUpdates;
   if (aReadback && UsedForReadback()) {
     aReadback->GetThebesLayerUpdates(this, &readbackUpdates);
   }
 
-  bool canUseOpaqueSurface = CanUseOpaqueSurface();
-  ContentType contentType =
-    canUseOpaqueSurface ? GFX_CONTENT_COLOR :
-                          GFX_CONTENT_COLOR_ALPHA;
   float opacity = GetEffectiveOpacity();
   gfxContext::GraphicsOperator mixBlendMode = GetEffectiveMixBlendMode();
 
@@ -158,54 +148,6 @@ BasicThebesLayer::PaintThebes(gfxContext* aContext,
     return;
   }
 
-  {
-    uint32_t flags = 0;
-#ifndef MOZ_WIDGET_ANDROID
-    if (BasicManager()->CompositorMightResample()) {
-      flags |= ThebesLayerBuffer::PAINT_WILL_RESAMPLE;
-    }
-    if (!(flags & ThebesLayerBuffer::PAINT_WILL_RESAMPLE)) {
-      if (MayResample()) {
-        flags |= ThebesLayerBuffer::PAINT_WILL_RESAMPLE;
-      }
-    }
-#endif
-    if (mDrawAtomically) {
-      flags |= ThebesLayerBuffer::PAINT_NO_ROTATION;
-    }
-    PaintState state =
-      mContentClient->BeginPaintBuffer(this, contentType, flags);
-    mValidRegion.Sub(mValidRegion, state.mRegionToInvalidate);
-
-    if (state.mContext) {
-      // The area that became invalid and is visible needs to be repainted
-      // (this could be the whole visible area if our buffer switched
-      // from RGB to RGBA, because we might need to repaint with
-      // subpixel AA)
-      state.mRegionToInvalidate.And(state.mRegionToInvalidate,
-                                    GetEffectiveVisibleRegion());
-      nsIntRegion extendedDrawRegion = state.mRegionToDraw;
-      SetAntialiasingFlags(this, state.mContext);
-
-      RenderTraceInvalidateStart(this, "FFFF00", state.mRegionToDraw.GetBounds());
-
-      PaintBuffer(state.mContext,
-                  state.mRegionToDraw, extendedDrawRegion, state.mRegionToInvalidate,
-                  state.mDidSelfCopy,
-                  aCallback, aCallbackData);
-      MOZ_LAYERS_LOG_IF_SHADOWABLE(this, ("Layer::Mutated(%p) PaintThebes", this));
-      Mutated();
-
-      RenderTraceInvalidateEnd(this, "FFFF00");
-    } else {
-      // It's possible that state.mRegionToInvalidate is nonempty here,
-      // if we are shrinking the valid region to nothing. So use mRegionToDraw
-      // instead.
-      NS_WARN_IF_FALSE(state.mRegionToDraw.IsEmpty(),
-                       "No context when we have something to draw, resource exhaustion?");
-    }
-  }
-
   if (BasicManager()->IsTransactionIncomplete())
     return;
 
@@ -242,6 +184,72 @@ BasicThebesLayer::PaintThebes(gfxContext* aContext,
   }
 }
 
+void
+BasicThebesLayer::Validate(LayerManager::DrawThebesLayerCallback aCallback,
+                           void* aCallbackData)
+{
+  if (!mContentClient) {
+    // we pass a null pointer for the Forwarder argument, which means
+    // this will not have a ContentHost on the other side.
+    mContentClient = new ContentClientBasic(nullptr, BasicManager());
+  }
+
+  if (!BasicManager()->IsRetained()) {
+    return;
+  }
+
+  bool canUseOpaqueSurface = CanUseOpaqueSurface();
+  ContentType contentType =
+    canUseOpaqueSurface ? GFX_CONTENT_COLOR :
+                          GFX_CONTENT_COLOR_ALPHA;
+
+  uint32_t flags = 0;
+#ifndef MOZ_WIDGET_ANDROID
+  if (BasicManager()->CompositorMightResample()) {
+    flags |= ThebesLayerBuffer::PAINT_WILL_RESAMPLE;
+  }
+  if (!(flags & ThebesLayerBuffer::PAINT_WILL_RESAMPLE)) {
+    if (MayResample()) {
+      flags |= ThebesLayerBuffer::PAINT_WILL_RESAMPLE;
+    }
+  }
+#endif
+  if (mDrawAtomically) {
+    flags |= ThebesLayerBuffer::PAINT_NO_ROTATION;
+  }
+  PaintState state =
+    mContentClient->BeginPaintBuffer(this, contentType, flags);
+  mValidRegion.Sub(mValidRegion, state.mRegionToInvalidate);
+
+  if (state.mContext) {
+    // The area that became invalid and is visible needs to be repainted
+    // (this could be the whole visible area if our buffer switched
+    // from RGB to RGBA, because we might need to repaint with
+    // subpixel AA)
+    state.mRegionToInvalidate.And(state.mRegionToInvalidate,
+                                  GetEffectiveVisibleRegion());
+    nsIntRegion extendedDrawRegion = state.mRegionToDraw;
+    SetAntialiasingFlags(this, state.mContext);
+
+    RenderTraceInvalidateStart(this, "FFFF00", state.mRegionToDraw.GetBounds());
+
+    PaintBuffer(state.mContext,
+                state.mRegionToDraw, extendedDrawRegion, state.mRegionToInvalidate,
+                state.mDidSelfCopy,
+                aCallback, aCallbackData);
+    MOZ_LAYERS_LOG_IF_SHADOWABLE(this, ("Layer::Mutated(%p) PaintThebes", this));
+    Mutated();
+
+    RenderTraceInvalidateEnd(this, "FFFF00");
+  } else {
+    // It's possible that state.mRegionToInvalidate is nonempty here,
+    // if we are shrinking the valid region to nothing. So use mRegionToDraw
+    // instead.
+    NS_WARN_IF_FALSE(state.mRegionToDraw.IsEmpty(),
+                     "No context when we have something to draw, resource exhaustion?");
+  }
+}
+
 already_AddRefed<ThebesLayer>
 BasicLayerManager::CreateThebesLayer()
 {

gfx/layers/basic/BasicThebesLayer.h

@@ -64,6 +64,9 @@ public:
                            void* aCallbackData,
                            ReadbackProcessor* aReadback);
 
+  virtual void Validate(LayerManager::DrawThebesLayerCallback aCallback,
+                        void* aCallbackData) MOZ_OVERRIDE;
+
   virtual void ClearCachedResources()
   {
     if (mContentClient) {