Bug 598538 - Reset the viewport rect when we create a temporary VBO, which can be bigger than the viewport! r=vlad a=b

gfx/layers/opengl/ContainerLayerOGL.cpp

@@ -169,9 +169,8 @@ ContainerLayerOGL::RenderLayer(int aPreviousFrameBuffer,
     childOffset.x = visibleRect.x;
     childOffset.y = visibleRect.y;
 
-    // Note that we don't set a new viewport here, even though we're
-    // about to render to a new FBO -- see the comments in
-    // LayerManagerOGL::SetupPipeline.
+    gl()->PushViewportRect();
+    mOGLManager->SetupPipeline(visibleRect.width, visibleRect.height);
 
     gl()->fScissor(0, 0, visibleRect.width, visibleRect.height);
     gl()->fClearColor(0.0, 0.0, 0.0, 0.0);
@@ -214,6 +213,12 @@ ContainerLayerOGL::RenderLayer(int aPreviousFrameBuffer,
 
   if (needsFramebuffer) {
     // Unbind the current framebuffer and rebind the previous one.
+    
+    // Restore the viewport
+    gl()->PopViewportRect();
+    nsIntRect viewport = gl()->ViewportRect();
+    mOGLManager->SetupPipeline(viewport.width, viewport.height);
+
     gl()->fBindFramebuffer(LOCAL_GL_FRAMEBUFFER, aPreviousFrameBuffer);
     gl()->fDeleteFramebuffers(1, &frameBuffer);
 

gfx/layers/opengl/LayerManagerOGL.cpp

@@ -671,20 +671,7 @@ LayerManagerOGL::Render()
 void
 LayerManagerOGL::SetupPipeline(int aWidth, int aHeight)
 {
-  // Set the viewport correctly.  Note that his viewport is used
-  // throughout the GL layers rendering pipeline, even when we're
-  // rendering to a FBO with different dimensions than the window.
-  // This means that we can set the viewMatrix once on every program
-  // (below).  When we render to a FBO (as in ContainerLayerOGL), we
-  // have to pass a correct child offset so that the coordinate system
-  // is translated appropriately to start at the origin of the FBO
-  // (or, put another way, so that the FBO looks to be at the right
-  // spot in the parent).
-  //
-  // Note: this effectively means that we can't really draw to a FBO
-  // that is bigger than the window dimensions.  This is fine for now,
-  // but might be a problem if we ever start doing GL drawing to
-  // retained layer FBOs that happen to retain more than is visible.
+  // Set the viewport correctly. 
   //
   // When we're not double buffering, we use a FBO as our backbuffer.
   // We use a normal view transform in that case, meaning that our FBO

gfx/layers/opengl/LayerManagerOGL.h

@@ -321,6 +321,12 @@ public:
     return mWidgetSize;
   }
   
+  /**
+   * Setup the viewport and projection matrix for rendering
+   * to a window of the given dimensions.
+   */
+  void SetupPipeline(int aWidth, int aHeight);
+
 private:
   /** Widget associated with this layer manager */
   nsIWidget *mWidget;
@@ -382,15 +388,12 @@ private:
    * Render the current layer tree to the active target.
    */
   void Render();
-  /**
-   * Setup the viewport and projection matrix for rendering
-   * to a window of the given dimensions.
-   */
-  void SetupPipeline(int aWidth, int aHeight);
+
   /**
    * Setup a backbuffer of the given dimensions.
    */
   void SetupBackBuffer(int aWidth, int aHeight);
+
   /**
    * Copies the content of our backbuffer to the set transaction target.
    */