Bug 580531 - Push ImageContainer subclass' locks up into a superclass monitor. r=roc

gfx/layers/ImageLayers.h

@@ -43,6 +43,7 @@
 #include "gfxPattern.h"
 #include "nsThreadUtils.h"
 #include "nsCoreAnimationSupport.h"
+#include "mozilla/Monitor.h"
 
 namespace mozilla {
 namespace layers {
@@ -131,7 +132,7 @@ class THEBES_API ImageContainer {
   THEBES_INLINE_DECL_THREADSAFE_REFCOUNTING(ImageContainer)
 
 public:
-  ImageContainer() {}
+  ImageContainer() : mMonitor("ImageContainer") {}
   virtual ~ImageContainer() {}
 
   /**
@@ -139,6 +140,8 @@ public:
    * Picks the "best" format from the list and creates an Image of that
    * format.
    * Returns null if this backend does not support any of the formats.
+   * Can be called on any thread. This method takes mMonitor when accessing
+   * thread-shared state.
    */
   virtual already_AddRefed<Image> CreateImage(const Image::Format* aFormats,
                                               PRUint32 aNumFormats) = 0;
@@ -146,6 +149,8 @@ public:
   /**
    * Set an Image as the current image to display. The Image must have
    * been created by this ImageContainer.
+   * Can be called on any thread. This method takes mMonitor when accessing
+   * thread-shared state.
    * 
    * The Image data must not be modified after this method is called!
    */
@@ -156,6 +161,8 @@ public:
    * This has to add a reference since otherwise there are race conditions
    * where the current image is destroyed before the caller can add
    * a reference.
+   * Can be called on any thread. This method takes mMonitor when accessing
+   * thread-shared state.
    */
   virtual already_AddRefed<Image> GetCurrentImage() = 0;
 
@@ -171,6 +178,8 @@ public:
    * Returns the size in aSize.
    * The returned surface will never be modified. The caller must not
    * modify it.
+   * Can be called on any thread. This method takes mMonitor when accessing
+   * thread-shared state.
    */
   virtual already_AddRefed<gfxASurface> GetCurrentAsSurface(gfxIntSize* aSizeResult) = 0;
 
@@ -187,13 +196,15 @@ public:
 
   /**
    * Returns the size of the image in pixels.
+   * Can be called on any thread. This method takes mMonitor when accessing
+   * thread-shared state.
    */
   virtual gfxIntSize GetCurrentSize() = 0;
 
   /**
    * Set a new layer manager for this image container.  It must be
    * either of the same type as the container's current layer manager,
-   * or null.  TRUE is returned on success.
+   * or null.  TRUE is returned on success. Main thread only.
    */
   virtual PRBool SetLayerManager(LayerManager *aManager) = 0;
 
@@ -201,20 +212,27 @@ public:
    * Sets a size that the image is expected to be rendered at.
    * This is a hint for image backends to optimize scaling.
    * Default implementation in this class is to ignore the hint.
+   * Can be called on any thread. This method takes mMonitor when accessing
+   * thread-shared state.
    */
   virtual void SetScaleHint(const gfxIntSize& /* aScaleHint */) { }
 
   /**
    * Get the layer manager type this image container was created with,
    * presumably its users might want to do something special if types do not
-   * match.
+   * match. Can be called on any thread.
    */
   virtual LayerManager::LayersBackend GetBackendType() = 0;
 
 protected:
+  typedef mozilla::Monitor Monitor;
   LayerManager* mManager;
 
-  ImageContainer(LayerManager* aManager) : mManager(aManager) {}
+  // Monitor to protect thread safe access to the "current image", and any
+  // other state which is shared between threads.
+  Monitor mMonitor;
+
+  ImageContainer(LayerManager* aManager) : mManager(aManager), mMonitor("ImageContainer")  {}
 };
 
 /**