Hold video frame in Bitmap instead of keeping a ByteBuffer reference.

remoting/android/java/src/org/chromium/chromoting/jni/JniInterface.java

Index: remoting/android/java/src/org/chromium/chromoting/jni/JniInterface.java
diff --git a/remoting/android/java/src/org/chromium/chromoting/jni/JniInterface.java b/remoting/android/java/src/org/chromium/chromoting/jni/JniInterface.java
index 98169703d0080c961925d9db59dce9183f6a8be7..02cdf8d7eebdd1ea31c9c15e03efca467bef530e 100644
--- a/remoting/android/java/src/org/chromium/chromoting/jni/JniInterface.java
+++ b/remoting/android/java/src/org/chromium/chromoting/jni/JniInterface.java
@@ -110,6 +110,9 @@ public class JniInterface {
                 sProgressIndicator.dismiss();
                 sProgressIndicator = null;
             }
+
+            // Drop the reference to free the Bitmap for GC.
+            sFrameBitmap = null;
         }
 
         disconnectNative();
@@ -136,17 +139,8 @@ public class JniInterface {
     /** Callback to signal whenever we need to redraw. */
     private static Runnable sRedrawCallback = null;
 
-    /** Screen width of the video feed. */
-    private static int sWidth = 0;
-
-    /** Screen height of the video feed. */
-    private static int sHeight = 0;
-
-    /** Bitmap holding the latest screen image. */
-    private static Bitmap sBitmap = null;
-
-    /** Buffer holding the video feed. */
-    private static ByteBuffer sBuffer = null;
+    /** Bitmap holding a copy of the latest video frame. */
+    private static Bitmap sFrameBitmap = null;
 
     /** Position of cursor hot-spot. */
     private static Point sCursorHotspot = new Point();
@@ -301,10 +295,10 @@ public class JniInterface {
     }
 
     /**
-     * Obtains the image buffer.
-     * This should not be called from the UI thread. (We prefer the native graphics thread.)
+     * Returns a bitmap of the latest video frame. Called on the native graphics thread when
+     * DesktopView is repainted.
      */
-    public static Bitmap retrieveVideoFrame() {
+    public static Bitmap getVideoFrame() {
         if (Looper.myLooper() == Looper.getMainLooper()) {
             Log.w("jniiface", "Canvas being redrawn on UI thread");
         }
@@ -313,19 +307,29 @@ public class JniInterface {
             return null;
         }
 
-        // This is synchronized only to silence a findbugs warning about incorrect initialization of
-        // |sBitmap|.
-        // TODO(lambroslambrou): Annotate this class as @NotThreadSafe to prevent similar warnings
-        // in future.
+        return sFrameBitmap;
+    }
+
+    /**
+     * Sets a new video frame. Called from native code on the native graphics thread when a new
+     * frame is allocated.
+     */
+    private static void setVideoFrame(Bitmap bitmap) {
+        if (Looper.myLooper() == Looper.getMainLooper()) {
+            Log.w("jniiface", "Video frame updated on UI thread");
+        }
+
         synchronized (JniInterface.class) {

[Yaron, 2013/10/09 06:42:30]

I believe this will trigger a findbugs error. We discouraging synchronizing on a
class object since they're effectively global and anyone can lock on it leading
to possible deadlocks. Instead, use a private member variable and lock on that.

[Lambros, 2013/10/10 01:35:58]

There are already lots of these in this file. I've fixed this one, but fixing
all the others is probably beyond the scope of this CL. Filed
https://code.google.com/p/chromium/issues/detail?id=305770

-            if (sBitmap == null || sBitmap.getWidth() != sWidth || sBitmap.getHeight() != sHeight) {
-                sBitmap = Bitmap.createBitmap(sWidth, sHeight, Bitmap.Config.ARGB_8888);
-            }
+            sFrameBitmap = bitmap;
         }
+    }
 
-        sBuffer.rewind();
-        sBitmap.copyPixelsFromBuffer(sBuffer);
-        return sBitmap;
+    /**
+     * Creates a new Bitmap to hold video frame pixels. Called by native code which stores a global
+     * reference to the Bitmap and writes the decoded frame pixels to it.
+     */
+    private static Bitmap newBitmap(int width, int height) {
+        return Bitmap.createBitmap(width, height, Bitmap.Config.ARGB_8888);
     }
 
     /**