Aura: Resize locks with --ui-enable-threaded-compositing

ui/compositor/compositor.h

Index: ui/compositor/compositor.h
diff --git a/ui/compositor/compositor.h b/ui/compositor/compositor.h
index ea5772480c321aaa0cc6146331827bcf56d675cf..756cd1674cff4d00cffa751c9210cd274a87bab7 100644
--- a/ui/compositor/compositor.h
+++ b/ui/compositor/compositor.h
@@ -126,6 +126,32 @@ class COMPOSITOR_EXPORT CompositorDelegate {
   virtual ~CompositorDelegate() {}
 };
 
+// This class represents a lock on the compositor, that can be used to prevent a
+// updates to the compositor tree while we're waiting for an asynchronous
+// event. The typical use case is when waiting for a renderer to produce a frame
+// at the right size. The caller keeps a reference on this object, and drops the
+// reference once it desires to release the lock.
+// Note however that the lock is canceled after a short timeout to ensure
+// responsiveness of the UI, so the compositor tree should be kept in a
+// "reasonable" state while the lock is held.
+// Don't instantiate this class directly, use Compositor::GetCompositorLock.
+class COMPOSITOR_EXPORT CompositorLock
+    : public base::RefCounted<CompositorLock>,
+      public base::SupportsWeakPtr<CompositorLock> {
+ private:
+  friend class base::RefCounted<CompositorLock>;
+  friend class Compositor;
+
+  explicit CompositorLock(Compositor* compositor);
+  ~CompositorLock();
+
+  void CancelLock();
+
+  Compositor* compositor_;
+  DISALLOW_COPY_AND_ASSIGN(CompositorLock);
+};
+
+
 // Compositor object to take care of GPU painting.
 // A Browser compositor object is responsible for generating the final
 // displayable form of pixels comprising a single widget's contents. It draws an
@@ -191,9 +217,8 @@ class COMPOSITOR_EXPORT Compositor
   // and the OnCompositingEnded.
   bool DrawPending() const { return swap_posted_; }
 
-  // Returns whether the drawing is issued from a separate thread
-  // (i.e. |Compositor::Initialize(true)| was called).
-  bool IsThreaded() const;
+  // Creates a compositor lock.
+  scoped_refptr<CompositorLock> GetCompositorLock();
 
   // Internal functions, called back by command-buffer contexts on swap buffer
   // events.
@@ -221,9 +246,14 @@ class COMPOSITOR_EXPORT Compositor
 
   int last_started_frame() { return last_started_frame_; }
   int last_ended_frame() { return last_ended_frame_; }
+  int last_commit_id() { return last_commit_id_; }
 
  private:
   friend class base::RefCounted<Compositor>;
+  friend class CompositorLock;
+
+  // Called by CompositorLock.
+  void Unlock();
 
   // When reading back pixel data we often get RGBA rather than BGRA pixels and
   // and the image often needs to be flipped vertically.
@@ -256,8 +286,25 @@ class COMPOSITOR_EXPORT Compositor
   int last_started_frame_;
   int last_ended_frame_;
 
+  int last_commit_id_;
+
   bool disable_schedule_composite_;
 
+  enum UpdatesAllowedState {
+    // We've told |root_layer_| to enable updates, but no update has cleared.

[piman, 2012/07/31 23:42:17]

"update" is a very overloaded term... Should we use "commit" instead (which has
a specific meaning in the compositor)? (for comments, and enum names)

[jonathan.backer, 2012/08/01 17:22:43]

Done.

+    ENABLED_NEEDS_UPDATE,
+    // We've updated since being enabled.
+    ENABLED_DID_UPDATE,
+    // We will tell |root_layer_| to defer updates once an update clears.
+    DISABLED_PENDING_UPDATE,
+    // We told |root_layer_| to disable updates.
+    DISABLED,
+  };
+
+  int updates_allowed_;

[piman, 2012/07/31 23:42:17]

UpdatesAllowedState instead of int?

[jonathan.backer, 2012/08/01 17:22:43]

Done.

+
+  CompositorLock* compositor_lock_;
+
   DISALLOW_COPY_AND_ASSIGN(Compositor);
 };