Adding disconnect call to the SurfaceTextureTarget

Related to b/5873421.
When an app using the SurfaceTextureTarget filter and the activity goes
out of focus such as onPause(), the underlying surfacetexture might not
be available anymore to the filter. The filter needs to be told about
that so that it does try to render into the surface corresponding to the
surfacetexture. For example, in Camera app, the VideoCamera activity has
to let the underlying effects graph know about the disconnect in the
onPause() method.

Change-Id: Iee3af16715432d84fef4438d1671f4d6d261b3d7

Author: psanketi

media/mca/filterpacks/java/android/filterpacks/videosrc/SurfaceTextureTarget.java

@@ -110,7 +110,7 @@ public SurfaceTextureTarget(String name) {
     }
 
     @Override
-    public void setupPorts() {
+    public synchronized void setupPorts() {
         // Make sure we have a SurfaceView
         if (mSurfaceTexture == null) {
             throw new RuntimeException("Null SurfaceTexture passed to SurfaceTextureTarget");
@@ -158,7 +158,7 @@ public void prepare(FilterContext context) {
     }
 
     @Override
-    public void open(FilterContext context) {
+    public synchronized void open(FilterContext context) {
         // Set up SurfaceTexture internals
         mSurfaceId = context.getGLEnvironment().registerSurfaceTexture(
             mSurfaceTexture, mScreenWidth, mScreenHeight);
@@ -169,17 +169,42 @@ public void open(FilterContext context) {
 
 
     @Override
-    public void close(FilterContext context) {
+    public synchronized void close(FilterContext context) {
         if (mSurfaceId > 0) {
             context.getGLEnvironment().unregisterSurfaceId(mSurfaceId);
+            mSurfaceId = -1;
+            // Once the surface is unregistered, remove the surfacetexture reference.
+            // The surfaceId could not have been valid without a valid surfacetexture.
+            mSurfaceTexture = null;
         }
     }
 
+    // This should be called from the client side when the surfacetexture is no longer
+    // valid. e.g. from onPause() in the application using the filter graph.
+    public synchronized void disconnect(FilterContext context) {
+        if (mLogVerbose) Log.v(TAG, "disconnect");
+        if (mSurfaceTexture == null) {
+            Log.d(TAG, "SurfaceTexture is already null. Nothing to disconnect.");
+            return;
+        }
+        mSurfaceTexture = null;
+        // Make sure we unregister the surface as well if a surface was registered.
+        // There can be a situation where the surface was not registered but the
+        // surfacetexture was valid. For example, the disconnect can be called before
+        // the filter was opened. Hence, the surfaceId may not be a valid one here,
+        // and need to check for its validity.
+        if (mSurfaceId > 0) {
+            context.getGLEnvironment().unregisterSurfaceId(mSurfaceId);
+            mSurfaceId = -1;
+        }
+    }
 
     @Override
-    public void process(FilterContext context) {
-        if (mLogVerbose) Log.v(TAG, "Starting frame processing");
-
+    public synchronized void process(FilterContext context) {
+        // Surface is not registered. Nothing to render into.
+        if (mSurfaceId <= 0) {
+            return;
+        }
         GLEnvironment glEnv = context.getGLEnvironment();
 
         // Get input frame
@@ -197,8 +222,6 @@ public void process(FilterContext context) {
 
         // See if we need to copy to GPU
         Frame gpuFrame = null;
-        if (mLogVerbose) Log.v("SurfaceTextureTarget", "Got input format: " + input.getFormat());
-
         int target = input.getFormat().getTarget();
         if (target != FrameFormat.TARGET_GPU) {
             gpuFrame = context.getFrameManager().duplicateFrameToTarget(input,