Bug 625672. Part 1.5: Make layer managers silently do nothing when ending a transaction with no root layer. r=bas,a=blocker

gfx/layers/Layers.h

@@ -348,7 +348,8 @@ public:
 
   /**
    * CONSTRUCTION PHASE ONLY
-   * Set the root layer.
+   * Set the root layer. The root layer is initially null. If there is
+   * no root layer, EndTransaction won't draw anything.
    */
   virtual void SetRoot(Layer* aLayer) = 0;
   /**

gfx/layers/basic/BasicLayers.cpp

@@ -1271,9 +1271,7 @@ BasicLayerManager::EndTransactionInternal(DrawThebesLayerCallback aCallback,
 
   mTransactionIncomplete = false;
 
-  if (mTarget) {
-    NS_ASSERTION(mRoot, "Root not set");
-
+  if (mTarget && mRoot) {
     nsRefPtr<gfxContext> finalTarget = mTarget;
     gfxPoint cachedSurfaceOffset;
 

gfx/layers/d3d10/LayerManagerD3D10.cpp

@@ -286,16 +286,19 @@ void
 LayerManagerD3D10::EndTransaction(DrawThebesLayerCallback aCallback,
                                   void* aCallbackData)
 {
-  mCurrentCallbackInfo.Callback = aCallback;
-  mCurrentCallbackInfo.CallbackData = aCallbackData;
+  if (mRoot) {
+    mCurrentCallbackInfo.Callback = aCallback;
+    mCurrentCallbackInfo.CallbackData = aCallbackData;
 
-  // The results of our drawing always go directly into a pixel buffer,
-  // so we don't need to pass any global transform here.
-  mRoot->ComputeEffectiveTransforms(gfx3DMatrix());
+    // The results of our drawing always go directly into a pixel buffer,
+    // so we don't need to pass any global transform here.
+    mRoot->ComputeEffectiveTransforms(gfx3DMatrix());
+
+    Render();
+    mCurrentCallbackInfo.Callback = nsnull;
+    mCurrentCallbackInfo.CallbackData = nsnull;
+  }
 
-  Render();
-  mCurrentCallbackInfo.Callback = nsnull;
-  mCurrentCallbackInfo.CallbackData = nsnull;
   mTarget = nsnull;
 }
 
@@ -499,9 +502,7 @@ LayerManagerD3D10::VerifyBufferSize()
 void
 LayerManagerD3D10::Render()
 {
-  if (mRoot) {
-    static_cast<LayerD3D10*>(mRoot->ImplData())->Validate();
-  }
+  static_cast<LayerD3D10*>(mRoot->ImplData())->Validate();
 
   SetupPipeline();
 
@@ -511,23 +512,21 @@ LayerManagerD3D10::Render()
   nsIntRect rect;
   mWidget->GetClientBounds(rect);
 
-  if (mRoot) {
-    const nsIntRect *clipRect = mRoot->GetClipRect();
-    D3D10_RECT r;
-    if (clipRect) {
-      r.left = (LONG)clipRect->x;
-      r.top = (LONG)clipRect->y;
-      r.right = (LONG)(clipRect->x + clipRect->width);
-      r.bottom = (LONG)(clipRect->y + clipRect->height);
-    } else {
-      r.left = r.top = 0;
-      r.right = rect.width;
-      r.bottom = rect.height;
-    }
-    device()->RSSetScissorRects(1, &r);
-
-    static_cast<LayerD3D10*>(mRoot->ImplData())->RenderLayer();
+  const nsIntRect *clipRect = mRoot->GetClipRect();
+  D3D10_RECT r;
+  if (clipRect) {
+    r.left = (LONG)clipRect->x;
+    r.top = (LONG)clipRect->y;
+    r.right = (LONG)(clipRect->x + clipRect->width);
+    r.bottom = (LONG)(clipRect->y + clipRect->height);
+  } else {
+    r.left = r.top = 0;
+    r.right = rect.width;
+    r.bottom = rect.height;
   }
+  device()->RSSetScissorRects(1, &r);
+
+  static_cast<LayerD3D10*>(mRoot->ImplData())->RenderLayer();
 
   if (mTarget) {
     PaintToTarget();

gfx/layers/d3d9/LayerManagerD3D9.cpp

@@ -173,17 +173,20 @@ LayerManagerD3D9::EndTransaction(DrawThebesLayerCallback aCallback,
 {
   mDeviceResetCount = mDeviceManager->GetDeviceResetCount();
 
-  mCurrentCallbackInfo.Callback = aCallback;
-  mCurrentCallbackInfo.CallbackData = aCallbackData;
+  if (mRoot) {
+    mCurrentCallbackInfo.Callback = aCallback;
+    mCurrentCallbackInfo.CallbackData = aCallbackData;
 
-  // The results of our drawing always go directly into a pixel buffer,
-  // so we don't need to pass any global transform here.
-  mRoot->ComputeEffectiveTransforms(gfx3DMatrix());
+    // The results of our drawing always go directly into a pixel buffer,
+    // so we don't need to pass any global transform here.
+    mRoot->ComputeEffectiveTransforms(gfx3DMatrix());
+
+    Render();
+    /* Clean this out for sanity */
+    mCurrentCallbackInfo.Callback = NULL;
+    mCurrentCallbackInfo.CallbackData = NULL;
+  }
 
-  Render();
-  /* Clean this out for sanity */
-  mCurrentCallbackInfo.Callback = NULL;
-  mCurrentCallbackInfo.CallbackData = NULL;
   // Clear mTarget, next transaction could have no target
   mTarget = NULL;
 }
@@ -270,23 +273,21 @@ LayerManagerD3D9::Render()
 
   device()->BeginScene();
 
-  if (mRoot) {
-    const nsIntRect *clipRect = mRoot->GetClipRect();
-    RECT r;
-    if (clipRect) {
-      r.left = (LONG)clipRect->x;
-      r.top = (LONG)clipRect->y;
-      r.right = (LONG)(clipRect->x + clipRect->width);
-      r.bottom = (LONG)(clipRect->y + clipRect->height);
-    } else {
-      r.left = r.top = 0;
-      r.right = rect.width;
-      r.bottom = rect.height;
-    }
-    device()->SetScissorRect(&r);
-
-    static_cast<LayerD3D9*>(mRoot->ImplData())->RenderLayer();
+  const nsIntRect *clipRect = mRoot->GetClipRect();
+  RECT r;
+  if (clipRect) {
+    r.left = (LONG)clipRect->x;
+    r.top = (LONG)clipRect->y;
+    r.right = (LONG)(clipRect->x + clipRect->width);
+    r.bottom = (LONG)(clipRect->y + clipRect->height);
+  } else {
+    r.left = r.top = 0;
+    r.right = rect.width;
+    r.bottom = rect.height;
   }
+  device()->SetScissorRect(&r);
+
+  static_cast<LayerD3D9*>(mRoot->ImplData())->RenderLayer();
 
   device()->EndScene();
 

gfx/layers/opengl/LayerManagerOGL.cpp

@@ -416,17 +416,19 @@ LayerManagerOGL::EndTransaction(DrawThebesLayerCallback aCallback,
     return;
   }
 
-  // The results of our drawing always go directly into a pixel buffer,
-  // so we don't need to pass any global transform here.
-  mRoot->ComputeEffectiveTransforms(gfx3DMatrix());
+  if (mRoot) {
+    // The results of our drawing always go directly into a pixel buffer,
+    // so we don't need to pass any global transform here.
+    mRoot->ComputeEffectiveTransforms(gfx3DMatrix());
 
-  mThebesLayerCallback = aCallback;
-  mThebesLayerCallbackData = aCallbackData;
+    mThebesLayerCallback = aCallback;
+    mThebesLayerCallbackData = aCallbackData;
 
-  Render();
+    Render();
 
-  mThebesLayerCallback = nsnull;
-  mThebesLayerCallbackData = nsnull;
+    mThebesLayerCallback = nsnull;
+    mThebesLayerCallbackData = nsnull;
+  }
 
   mTarget = NULL;