DialogSurfaceManager implementation.

media/base/android/java/src/org/chromium/media/DialogSurfaceManagerImpl.java

+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+package org.chromium.media;
+
+import android.content.Context;
+import android.os.Handler;
+import android.os.HandlerThread;
+import android.os.IBinder;
+
+import org.chromium.base.ContextUtils;
+import org.chromium.base.annotations.CalledByNative;
+import org.chromium.base.annotations.JNINamespace;
+
+/**
+ * Singleton class to create and manage DialogSurface.  Normally, you won't need
+ * to access this directly.  Instead, see the native wrappers in
+ * dialog_surface_manager.cc for usage.
+ *
+ * The wrappers do roughly the following on the gpu side:
+ *  - Create an IDialogSurfaceCallback.  For native, DialogSurfaceCallback hides
+ *    the threading issues and provides the java peer.
+ *  - Get an IDialogSurfaceManager from the browser via ChildProcessCallback .
+ *  - dialogSurface = IDialogSurfaceManager.createSurface(callback)
+ *    This calls into the browser, and returns an IDialogSurface IBinder.
+ *  - Wrap the DialogSurface in a DialogSurfaceWrapper.  This provides the JNI
+ *    bindings for native.
+ *  - Expect callbacks on the callback to let you know when the underlying
+ *    android surface state changes.
+ *  - Use the surface.
+ *  - Call IDialogSurface::release() to destroy the surface when done.
+ */
+@JNINamespace("media")
+public class DialogSurfaceManagerImpl extends IDialogSurfaceManager.Stub {
+    private static final String TAG = "cr_media";
+    private static DialogSurfaceManagerImpl sInstance;
+    private static final Object sLock = new Object();
+
+    private final Context mContext;
+
+    // We maintain a thread with a Looper for the DialogSurfaces to use,
+    // since Dialog requires one.  We don't want this to be the native thread
+    // that's used to create them, because it probably also has a native message
+    // loop.  Including a looper on it is not a good idea.

[boliu, 2017/01/04 23:14:39]

the browser UI thread does have a java looper, so if this is only ever runs in
the browser, can just use the UI thread

[liberato (no reviews please), 2017/01/11 22:17:57]

i want to avoid that so that synchronous callbacks for surface destruction don't
block the ui thread.  i'll update the comment to make that clearer.

[boliu, 2017/01/12 20:24:19]

Ahh, I was curious what surface view implement, but it looks like it doesn't
bother waiting for gpu to clean up at all? So is blocking in destroy really
necessary? perhaps the gpu code is already robust enough to handle this?

[liberato (no reviews please), 2017/02/03 21:28:32]

i'll have to dig up where it does this, but CVV does require sync cleanup, and
does wait during IPC to the gpu for it to finish.  it's required, else media
codec can crash.

+    private final Object mLock = new Object();
+    private HandlerThread mThread;
+    private Handler mHandler;
+    // TODO(liberato): why does this have to be a binder interface?  i suppose
+    // it has to live in the browser process.  however, it's a lot more
+    // convenient if we don't need a binder object for it to call back on.
+    // maybe we should just make it a normal interface with inner client.
+    private final DialogSurfaceWindowTokenProvider mTokenProvider;
+
+    // Number of DialogSurfaces that have been created but not released.
+    private int mNumSurfaces;
+
+    // Maximum number of concurrent surfaces we allow.
+    private static final int MAX_SURFACES = 1;
+
+    private DialogSurfaceManagerImpl(DialogSurfaceWindowTokenProvider tokenProvider) {
+        mContext = ContextUtils.getApplicationContext();
+        mTokenProvider = tokenProvider;
+        mNumSurfaces = 0;
+    }
+
+    // Return the singleton instance, as a convenience.
+    public static IBinder instance(DialogSurfaceWindowTokenProvider tokenProvider) {
+        synchronized (sLock) {
+            if (sInstance == null) sInstance = new DialogSurfaceManagerImpl(tokenProvider);
+
+            return sInstance.asBinder();
+        }
+    }
+
+    @Override
+    @CalledByNative

[boliu, 2017/01/04 01:48:44]

this class doesn't generate jni code?

[liberato (no reviews please), 2017/01/11 22:17:57]

whoops.  thanks.

+    public IDialogSurface createSurface(int rendererPid, int renderFrameId,
+            IDialogSurfaceCallback callback, int x, int y, int width, int height) {
+        // Note that we may be called on any random binder thread, so lock.
+        synchronized (mLock) {
+            // Limit the number of concurrent surfaces.
+            if (mNumSurfaces >= MAX_SURFACES) return null;
+
+            startThreadIfNeededLocked();
+
+            mNumSurfaces++;
+        }
+
+        return new DialogSurfaceImpl(rendererPid, renderFrameId, mContext, this, mHandler, callback,
+                x, y, width, height);
+    }
+
+    /**
+     * Called by DialogSurfaces when they no longer need the thread.
+     * Called on some random thread.
+     */
+    public void notifyReleased() {
+        synchronized (mLock) {
+            if (mNumSurfaces > 0) mNumSurfaces--;

[boliu, 2017/01/04 01:48:44]

this should be an assert? (which works as DCHECKs now, apparently)

[liberato (no reviews please), 2017/01/11 22:17:57]

Done.

+
+            // We don't stop the looper thread here, else android can get mad when
+            // it tries to send a message from the dialog on this thread.
+            // DialogSurface might have to notify us separately to tell us
+            // when it's done with the thread, if we don't want to wait until then
+            // to start creating a new SV.
+            // Instead, we just avoid shutting down the thread at all for now.
+        }
+    }
+
+    /**
+     * Make sure that mThread and mHandler are ready for use.  Do nothing if
+     * they already are.
+     */
+    private void startThreadIfNeededLocked() {
+        // Called with mLock held only.
+        if (mThread != null) return;
+
+        mThread = new HandlerThread("DialogSurfaceThread");
+        mThread.start();
+        mHandler = new Handler(mThread.getLooper());
+    }
+
+    /**
+     * Return the window token provider.
+     */
+    public DialogSurfaceWindowTokenProvider getWindowTokenProvider() {
+        return mTokenProvider;
+    }
+}