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|m

[Ted C, 2017/01/31 23:17:51]

there seems to be a trailing m after the final |

[liberato (no reviews please), 2017/02/01 19:19:48]

thanks.  vim column bar @100 is the same color as the syntax-highlighted comment
text.

+        // 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 donwWithUnownedSurface

[Ted C, 2017/01/31 23:17:50]

s/donw/done

[liberato (no reviews please), 2017/02/01 19:19:48]

vim column bar @80 is... maybe i should change the color of those bars.

+        // when it is safe to do that.
+        disownClientSurface(mOwnedByClient);

[Ted C, 2017/01/31 23:17:50]

Would it be better to post this block of code to make the client api more
predictable (by calling this method you're not sure if you'll get an immediate
callback or a posted one).  I don't know if imposing the same async behavior
across both call sites makes this more difficult though (where you then have to
track even more state).

If I understand this correctly, this is purely for the path where low end phones
doesn't actually change their surface format but we need to destroy the native
surface for the changes to take effect.

[liberato (no reviews please), 2017/02/01 19:19:47]

i think that there are other cases, though rare.  if one requests A, B, A
without sending doneWith... for A, then it'll also get here since the surface is
still ready.

i like the idea of a simpler api.  i need to think what happens if
mOwnedByClient is set to null while a posted synthetic surfaceDestroyed is in
flight.  i'd like to avoid cases where some surfaceCreated arrives first at the
client.

it might work as it is, since android sends these things async anyway.  i'm
afraid that we'd end up with 'disownInProgress' and 'ownInProgress' flags to
keep things sorted.

if that turns out to be true, then i'll leave it as is.  otherwise, i'll post
the reply.

update: can't convince myself.  pretty sure that multiple requests could get
confusing.

+
+        // 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);
+    }
+
+    /**
+     * 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.
+

[Ted C, 2017/01/31 23:17:50]

remove blank line

[liberato (no reviews please), 2017/02/01 19:19:48]

Done.

+            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);
+            }
+        });
+    }
+}