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.os.Handler;
+import android.os.HandlerThread;
+import android.os.IBinder;
+
+import org.chromium.base.UnguessableToken;
+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();
+
+    // 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.
+    private final Object mLock = new Object();
+    private HandlerThread mThread;
+    private Handler mHandler;
+    private final IDialogSurfaceActivityMapper mMapper;
+
+    // Number of DialogSurfaces that have been created but not released.
+    private int mNumSurfaces;
+
+    // Maximum number of concurrent surfaces we allow.
+    private static final int sMaxSurfaces = 1;

[boliu, 2016/11/14 16:39:25]

stype: MAX_SURFACES

[liberato (no reviews please), 2016/12/20 17:16:38]

Done.

+
+    private DialogSurfaceManagerImpl(IDialogSurfaceActivityMapper mapper) {
+        mMapper = mapper;
+        mNumSurfaces = 0;
+    }
+
+    // Return the singleton instance, as a convenience.
+    public static IBinder instance(IDialogSurfaceActivityMapper mapper) {
+        synchronized (sLock) {
+            if (sInstance == null) sInstance = new DialogSurfaceManagerImpl(mapper);
+
+            return sInstance.asBinder();
+        }
+    }
+
+    @Override
+    @CalledByNative
+    public IDialogSurfaceHolder createSurface(UnguessableToken frameToken,
+            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 >= sMaxSurfaces) return null;
+
+            // TODO(liberato): would get the WindowToken / Activity here.
+
+            startThreadIfNeededLocked();
+
+            mNumSurfaces++;
+        }
+
+        // TODO(liberato): would instantiate DialogSurfaceHolder here.
+        return null;
+    }
+
+    /**
+     * Called by DialogSurfaces when they no longer need the thread.
+     */
+    public void notifyReleased() {
+        synchronized (mLock) {
+            if (mNumSurfaces > 0) mNumSurfaces--;
+
+            // 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;
+
+        // Just to avoid "Unread field" in findbugs.  Normally, we wills send
+        // mHandler to DialogSurface.
+        if (mHandler != null) return;
+
+        mThread = new HandlerThread("DialogSurfaceThread");
+        mThread.start();
+        mHandler = new Handler(mThread.getLooper());
+    }
+
+    /**
+     * Return the activity mapper.
+     */
+    public IDialogSurfaceActivityMapper getMapper() {
+        return mMapper;
+    }
+}