Improve transition between opaque and translucent compositor views.

chrome/android/java/src/org/chromium/chrome/browser/compositor/CompositorSurfaceManager.java

+// Copyright 2017 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.chrome.browser.compositor;
+
+import android.content.Context;
+import android.graphics.PixelFormat;
+import android.graphics.drawable.Drawable;
+import android.view.SurfaceHolder;
+import android.view.SurfaceView;
+import android.view.View;
+import android.view.ViewGroup;
+import android.widget.FrameLayout;
+
+/**
+ * Manage multiple SurfaceViews for the compositor, so that transitions between
+ * surfaces with and without an alpha channel can be visually smooth.
+ *
+ * This class allows a client to request a 'translucent' or 'opaque' surface, and we will signal via
+ * SurfaceHolder.Callback when it's ready.  We guarantee that the client will receive surfaceCreated
+ * / surfaceDestroyed only for a surface that represents the most recently requested PixelFormat.
+ *
+ * Internally, we maintain two SurfaceViews, since calling setFormat() to change the PixelFormat
+ * results in a visual glitch as the surface is torn down.  crbug.com/679902
+ *
+ * The client has the responsibility to call doneWithUnownedSurface() at some point between when we
+ * call back its surfaceCreated, when it is safe for us to hide the SurfaceView with the wrong
+ * format.  It is okay if it requests multiple surfaces without calling doneWithUnownedSurface.
+ *
+ * If the client requests the same format more than once in a row, it will still receive destroyed /
+ * created / changed messages for it, even though we won't tear it down.
+ *
+ * The full design doc is at https://goo.gl/aAmQzR .
+ */
+class CompositorSurfaceManager implements SurfaceHolder.Callback {
+    private static class SurfaceState {
+        public SurfaceView surfaceView;
+
+        // Do we expect a surfaceCreated?
+        public boolean createPending;
+
+        // Have we started destroying |surfaceView|, but haven't received surfaceDestroyed yet?
+        public boolean destroyPending;
+
+        // Last PixelFormat that we received, or UNKNOWN if we don't know / don't want to cache it.
+        public int format;
+
+        // Last known width, height for thsi surface.
+        public int width;
+        public int height;
+
+        // Parent ViewGroup, or null.
+        private ViewGroup mParent;
+
+        public SurfaceState(Context context, int format, SurfaceHolder.Callback callback) {
+            surfaceView = new SurfaceView(context);
+            surfaceView.setZOrderMediaOverlay(true);
+            surfaceView.setVisibility(View.VISIBLE);
+            surfaceHolder().setFormat(format);
+            surfaceHolder().addCallback(callback);
+
+            // Set this to UNKNOWN until we get a format back.
+            this.format = PixelFormat.UNKNOWN;
+        }
+
+        public SurfaceHolder surfaceHolder() {
+            return surfaceView.getHolder();
+        }
+
+        public boolean isValid() {
+            return surfaceHolder().getSurface().isValid();
+        }
+
+        // Attach to |parent|, such that isAttached() will be correct immediately.  Otherwise,
+        // attaching and detaching can cause surfaceCreated / surfaceDestroyed callbacks without
+        // View.hasParent being up to date.
+        public void attachTo(ViewGroup parent, FrameLayout.LayoutParams lp) {
+            mParent = parent;
+            mParent.addView(surfaceView, lp);
+        }
+
+        public void detachFromParent() {
+            final ViewGroup parent = mParent;
+            // Since removeView can call surfaceDestroyed before returning, be sure that isAttached
+            // will return false.
+            mParent = null;
+            parent.removeView(surfaceView);
+        }
+
+        public boolean isAttached() {
+            return mParent != null;
+        }
+    }
+
+    // SurfaceView with a translucent PixelFormat.
+    private final SurfaceState mTranslucent;
+
+    // SurfaceView with an opaque PixelFormat.
+    private final SurfaceState mOpaque;
+
+    // Surface that we last gave to the client with surfaceCreated.  Cleared when we call
+    // surfaceDestroyed on |mClient|.  Note that it's not necessary that Android has notified us
+    // the surface has been destroyed; we deliberately keep it around until the client tells us that
+    // it's okay to get rid of it.
+    private SurfaceState mOwnedByClient;
+
+    // Surface that was most recently requested by the client.
+    private SurfaceState mRequestedByClient;
+
+    // Client that we notify about surface change events.
+    private SurfaceHolder.Callback mClient;
+
+    // View to which we'll attach the SurfaceView.
+    private final ViewGroup mParentView;
+
+    public CompositorSurfaceManager(ViewGroup parentView, SurfaceHolder.Callback client) {
+        mParentView = parentView;
+        mClient = client;
+
+        mTranslucent = new SurfaceState(parentView.getContext(), PixelFormat.TRANSLUCENT, this);
+        mOpaque = new SurfaceState(mParentView.getContext(), PixelFormat.OPAQUE, this);
+    }
+
+    /**
+     * Turn off everything.
+     */
+    public void shutDown() {
+        mTranslucent.surfaceHolder().removeCallback(this);
+        mOpaque.surfaceHolder().removeCallback(this);
+    }
+
+    /**
+     * Called by the client to request a surface.  Once called, we guarantee that the next call to
+     * surfaceCreated will match the most recent value of |format|.  If the surface is already
+     * available for use, then we'll send synthetic callbacks as though it were destroyed and
+     * recreated.  Note that |format| must be either OPAQUE or TRANSLUCENT.
+     */
+    public void requestSurface(int format) {
+        mRequestedByClient = (format == PixelFormat.TRANSLUCENT) ? mTranslucent : mOpaque;
+
+        // If destruction is pending, then we must wait for it to complete.  When we're notified
+        // that it is destroyed, we'll re-start construction if the client still wants this surface.
+        // Note that we could send a surfaceDestroyed for the owned surface, if there is one, but we
+        // defer it until later so that the client can still use it until the new one is ready.
+        if (mRequestedByClient.destroyPending) return;
+
+        // The requested surface isn't being torn down.
+
+        // If the surface isn't attached yet, then attach it.  Otherwise, we're still waiting for
+        // the surface to be created, or we've already received surfaceCreated for it.
+        if (!mRequestedByClient.isAttached()) {
+            attachSurfaceNow(mRequestedByClient);
+            assert mRequestedByClient.isAttached();
+            return;
+        }
+
+        // Surface is not pending destroy, and is attached.  See if we need to send any synthetic
+        // callbacks to the client.  If we're expecting a callback from Android, then we'll handle
+        // it when it arrives instead.
+        if (mRequestedByClient.createPending) return;
+
+        // Surface is attached and no create is pending.  Send a synthetic create.  Note that, if
+        // Android destroyed the surface itself, then we'd have set |createPending| at that point.
+        // We don't check |isValid| here, since, technically, there could be a destroy in flight
+        // from Android.  It's okay; we'll just notify the client at that point.  Either way, we
+        // must tell the client that it now owns the surface.
+
+        // Send a notification about any owned surface.  Note that this can be |mRequestedByClient|
+        // which is fine.  We'll send destroy / create for it.  Also note that we don't actually
+        // start tear-down of the owned surface; the client notifies us via doneWithUnownedSurface
+        // when it is safe to do that.
+        disownClientSurface(mOwnedByClient);
+
+        // The client now owns |mRequestedByClient|.  Notify it that it's ready.
+        mOwnedByClient = mRequestedByClient;
+        mClient.surfaceCreated(mOwnedByClient.surfaceHolder());
+
+        // See if we're expecting a surfaceChanged.  If not, then send a synthetic one.
+        if (mOwnedByClient.format != PixelFormat.UNKNOWN) {
+            mClient.surfaceChanged(mOwnedByClient.surfaceHolder(), mOwnedByClient.width,
+                    mOwnedByClient.height, mOwnedByClient.format);
+        }
+    }
+
+    /**
+     * Called to notify us that the client no longer needs the surface that it doesn't own.  This
+     * tells us that we may destroy it.  Note that it's okay if it never had an unowned surface.
+     */
+    public void doneWithUnownedSurface() {
+        if (mOwnedByClient == null) return;
+
+        SurfaceState unowned = (mOwnedByClient == mTranslucent) ? mOpaque : mTranslucent;
+
+        if (mRequestedByClient == unowned) {
+            // Client is giving us back a surface that it's since requested but hasn't gotten yet.
+            // Do nothing.  It will be notified when the new surface is ready, and it can call us
+            // again for the other surface, if it wants.
+            return;
+        }
+
+        // Start destruction of this surface.  To prevent recursive call-backs to the client, we
+        // post this for later.
+        detachSurfaceLater(unowned);
+    }
+
+    /**
+     * Return the currently owned SurfaceHolder, if any.
+     */
+    public SurfaceHolder getHolder() {
+        return mOwnedByClient != null ? mOwnedByClient.surfaceHolder() : null;
+    }
+
+    /**
+     * Destroy and re-create the surface.  Useful for a JB workaround needed by CompositorView.
+     */
+    public void recreateSurfaceForJellyBean() {
+        // If they don't have a surface, then they'll get a new one anyway.
+        if (mOwnedByClient == null) return;
+
+        // Notify the client that it no longer owns this surface, then destroy it.  When destruction
+        // completes, we will recreate it automatically, since it will look like the client since
+        // re-requested it.  That's why we send surfaceDestroyed here rather than letting our
+        // surfaceDestroyed do it when destruction completes.  If we just started destruction while
+        // the client still owns the surface, then our surfaceDestroyed would assume that Android
+        // initiated the destruction, and wait for Android to recreate it.
+
+        mParentView.post(new Runnable() {
+            @Override
+            public void run() {
+                if (mOwnedByClient == null) return;
+                SurfaceState owned = mOwnedByClient;
+                mClient.surfaceDestroyed(mOwnedByClient.surfaceHolder());
+                mOwnedByClient = null;
+                detachSurfaceNow(owned);
+            }
+        });
+    }
+
+    @Override
+    public void surfaceChanged(SurfaceHolder holder, int format, int width, int height) {
+        SurfaceState state = getStateForHolder(holder);
+        assert state != null;
+
+        // If this is the surface that the client currently cares about, then notify the client.
+        // Note that surfaceChanged is guaranteed to come only after surfaceCreated.  Also, if the
+        // client has requested a different surface but hasn't gotten it yet, then skip this.
+        if (state == mOwnedByClient && state == mRequestedByClient) {
+            state.width = width;
+            state.height = height;
+            state.format = format;
+            mClient.surfaceChanged(holder, format, width, height);
+        }
+    }
+
+    @Override
+    public void surfaceCreated(SurfaceHolder holder) {
+        SurfaceState state = getStateForHolder(holder);
+        assert state != null;
+        // Note that |createPending| might not be set, if Android destroyed and recreated this
+        // surface on its own.
+
+        if (state != mRequestedByClient) {
+            // Surface is created, but it's not the one that's been requested most recently.  Just
+            // destroy it again.
+            detachSurfaceLater(state);
+            return;
+        }
+
+        // No create is pending.
+        state.createPending = false;
+
+        // A surfaceChanged should arrive.
+        state.format = PixelFormat.UNKNOWN;
+
+        // The client requested a surface, and it's now available.  If the client owns a surface,
+        // then notify it that it doesn't.  Note that the client can't own |state| at this point,
+        // since we would have removed ownership when we got surfaceDestroyed.  It's okay if the
+        // client doesn't own either surface.
+        assert mOwnedByClient != state;
+        disownClientSurface(mOwnedByClient);
+
+        // The client now owns this surface, so notify it.
+        mOwnedByClient = mRequestedByClient;
+        mClient.surfaceCreated(mOwnedByClient.surfaceHolder());
+    }
+
+    @Override
+    public void surfaceDestroyed(SurfaceHolder holder) {
+        SurfaceState state = getStateForHolder(holder);
+        assert state != null;
+
+        // If no destroy is pending, then Android chose to destroy this surface and will, hopefully,
+        // re-create it at some point.  Otherwise, a destroy is either posted or has already
+        // detached this SurfaceView.  If it's already detached, then the destruction is complete
+        // and we can clear |destroyPending|.  Otherwise, Android has destroyed this surface while
+        // our destroy was posted, and might even return it before it runs.  When the post runs, it
+        // can sort that out based on whether the surface is valid or not.
+        if (!state.destroyPending) {
+            state.createPending = true;
+        } else if (!state.isAttached()) {
+            state.destroyPending = false;
+        }
+
+        state.format = PixelFormat.UNKNOWN;
+
+        // If the client owns this surface, then notify it synchronously that it no longer does.
+        // This can happen if Android destroys the surface on its own.  It's also possible that
+        // we've detached it, if a destroy was pending.  Either way, notify the client.
+        if (state == mOwnedByClient) {
+            disownClientSurface(mOwnedByClient);
+
+            // Do not re-request the surface here.  If android gives the surface back, then we'll
+            // re-signal the client about construction.
+            return;
+        }
+
+        // The client doesn't own this surface, but might want it.
+        // If the client has requested this surface, then start construction on it.  The client will
+        // be notified when it completes.  This can happen if the client re-requests a surface after
+        // we start destruction on it from a previous request, for example.  We post this for later,
+        // since we might be called while removing |state| from the view tree. In general, posting
+        // from here is good.
+        if (state == mRequestedByClient && !state.isAttached()) {
+            attachSurfaceLater(state);
+        } else if (state != mRequestedByClient && state.isAttached()) {
+            // This isn't the requested surface.  If android destroyed it, then also unhook it so
+            // that it isn't recreated later.
+            detachSurfaceLater(state);
+        }
+    }
+
+    /**
+     * Update the background drawable on all surfaces.
+     */
+    public void setBackgroundDrawable(Drawable background) {
+        mTranslucent.surfaceView.setBackgroundDrawable(background);
+        mOpaque.surfaceView.setBackgroundDrawable(background);
+    }
+
+    /**
+     * Set |willNotDraw| on all surfaces.
+     */
+    public void setWillNotDraw(boolean willNotDraw) {
+        mTranslucent.surfaceView.setWillNotDraw(willNotDraw);
+        mOpaque.surfaceView.setWillNotDraw(willNotDraw);
+    }
+
+    public void setVisibility(int visibility) {
+        mTranslucent.surfaceView.setVisibility(visibility);
+        mOpaque.surfaceView.setVisibility(visibility);
+    }
+
+    /**
+     * Return the SurfaceState for |holder|, or null if it isn't either.
+     */
+    private SurfaceState getStateForHolder(SurfaceHolder holder) {
+        if (mTranslucent.surfaceHolder() == holder) return mTranslucent;
+
+        if (mOpaque.surfaceHolder() == holder) return mOpaque;
+
+        return null;
+    }
+
+    /**
+     * Attach |state| to |mParentView| immedaitely.
+     */
+    private void attachSurfaceNow(SurfaceState state) {
+        if (state.isAttached()) return;
+
+        // If there is a destroy in-flight for this surface, then do nothing.
+        if (state.destroyPending) return;
+
+        state.createPending = true;
+        FrameLayout.LayoutParams lp = new FrameLayout.LayoutParams(
+                ViewGroup.LayoutParams.MATCH_PARENT, ViewGroup.LayoutParams.MATCH_PARENT);
+        state.attachTo(mParentView, lp);
+        mParentView.bringChildToFront(state.surfaceView);
+        mParentView.postInvalidateOnAnimation();
+    }
+
+    /**
+     * Post a Runnable to attach |state|.  This is helpful, since one cannot directly interact with
+     * the View heirarchy during Surface callbacks.
+     */
+    private void attachSurfaceLater(final SurfaceState state) {
+        // We shouldn't try to post construction if there's an in-flight destroy.
+        assert !state.destroyPending;
+        state.createPending = true;
+
+        mParentView.post(new Runnable() {
+            @Override
+            public void run() {
+                attachSurfaceNow(state);
+            }
+        });
+    }
+
+    /**
+     * Cause the client to disown |state| if it currently owns it.  This involves notifying it that
+     * the surface has been destroyed (recall that ownership involves getting created).  It's okay
+     * if |state| is null or isn't owned by the client.
+     */
+    private void disownClientSurface(SurfaceState state) {
+        if (mOwnedByClient != state || state == null) return;
+
+        mClient.surfaceDestroyed(mOwnedByClient.surfaceHolder());
+        mOwnedByClient = null;
+    }
+
+    /**
+     * Detach |state| from |mParentView| immediately.
+     */
+    private void detachSurfaceNow(SurfaceState state) {
+        // If we're called while we're not attached, then do nothing.  This makes it easier for the
+        // client, since it doesn't have to keep track of whether the outgoing surface has been
+        // destroyed or not.  The client will be notified (or has already) when the surface is
+        // destroyed, if it currently owns it.
+        if (state.isAttached()) {
+            // We are attached.  If the surface is not valid, then Android has destroyed it for some
+            // other reason, and we should clean up.  Otherwise, just wait for Android to finish.
+            final boolean valid = state.isValid();
+
+            // If the surface is valid, then we expect a callback to surfaceDestroyed eventually.
+            state.destroyPending = valid;
+
+            // Note that this might call back surfaceDestroyed before returning!
+            state.detachFromParent();
+
+            // If the surface was valid before, then we expect a surfaceDestroyed callback, which
+            // might have arrived during removeView.  Either way, that callback will finish cleanup
+            // of |state|.
+            if (valid) return;
+        }
+
+        // The surface isn't attached, or was attached but wasn't currently valid.  Either way,
+        // we're not going to get a destroy, so notify the client now if needed.
+        disownClientSurface(state);
+
+        // If the client has since re-requested the surface, then start construction.
+        if (state == mRequestedByClient) attachSurfaceNow(mRequestedByClient);
+    }
+
+    /**
+     * Post detachment of |state|.  This is safe during Surface callbacks.
+     */
+    private void detachSurfaceLater(final SurfaceState state) {
+        // If |state| is not attached, then do nothing.  There might be a destroy pending from
+        // Android, but in any case leave it be.
+        if (!state.isAttached()) return;
+
+        state.destroyPending = true;
+        mParentView.post(new Runnable() {
+            @Override
+            public void run() {
+                detachSurfaceNow(state);
+            }
+        });
+    }
+}