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Commit 53c47d1d authored by Alec Mouri's avatar Alec Mouri
Browse files

Allow for synchronously applying transactions with a SurfaceView 

Exposing this allows for atomically updating a SurfaceControl hierarchy
when new frames arrive as the SurfaceView's content. For instance, a
streaming application can blank out the Surface when switching video
source files to prevent older frames from lingering.

Bug: 187309567
Test: SurfaceViewTests
Change-Id: I9b4df8b3312506f014f97c7f4a890b8242578ede
parent 0eb1f982

core/api/current.txt

+1 −0
Original line number Diff line number Diff line
@@ -51451,6 +51451,7 @@ package android.view { 
    ctor public SurfaceView(android.content.Context, android.util.AttributeSet);

    ctor public SurfaceView(android.content.Context, android.util.AttributeSet, int);

    ctor public SurfaceView(android.content.Context, android.util.AttributeSet, int, int);

    method public void applyTransactionToFrame(@NonNull android.view.SurfaceControl.Transaction);

    method public android.view.SurfaceHolder getHolder();

    method @Nullable public android.os.IBinder getHostToken();

    method public android.view.SurfaceControl getSurfaceControl();

core/java/android/view/SurfaceView.java

+36 −2
Original line number Diff line number Diff line
@@ -1756,8 +1756,14 @@ public class SurfaceView extends View implements ViewRootImpl.SurfaceChangedCall 
    };



    /**

     * Return a SurfaceControl which can be used for parenting Surfaces to

     * this SurfaceView.

     * Return a SurfaceControl which can be used for parenting Surfaces to this SurfaceView.

     *

     * Note that this SurfaceControl is effectively read-only. Its only well-defined usage is in

     * using the SurfaceControl as a parent for an application's hierarchy of SurfaceControls. All

     * other properties of the SurfaceControl, such as its position, may be mutated by the

     * SurfaceView at any time which will override what the application is requesting. Do not apply

     * any {@link SurfaceControl.Transaction} to this SurfaceControl except for reparenting

     * child SurfaceControls. See: {@link SurfaceControl.Transaction#reparent}.

     *

     * @return The SurfaceControl for this SurfaceView.

     */
@@ -1983,4 +1989,32 @@ public class SurfaceView extends View implements ViewRootImpl.SurfaceChangedCall 
    public void syncNextFrame(Consumer<Transaction> t) {

        mBlastBufferQueue.syncNextTransaction(t);

    }



    /**

     * Adds a transaction that would be applied synchronously with displaying the SurfaceView's next

     * frame.

     *

     * Note that the exact frame that the transaction is applied with is only well-defined when

     * SurfaceView rendering is paused prior to calling applyTransactionToFrame(), so that the

     * transaction is applied with the next frame rendered after applyTransactionToFrame() is

     * called. If frames are continuously rendering to the SurfaceView when

     * applyTransactionToFrame() is called, then it is undefined which frame the transaction is

     * applied with. It is also possible for the transaction to not be applied if no new frames are

     * rendered to the SurfaceView after this is called.

     *

     * @param transaction The transaction to apply. The system takes ownership of the transaction

     *                    and promises to eventually apply the transaction.

     * @throws IllegalStateException if the underlying Surface does not exist (and therefore

     *         there is no next frame).

     */

    public void applyTransactionToFrame(@NonNull SurfaceControl.Transaction transaction) {

        synchronized (mSurfaceControlLock) {

            if (mBlastBufferQueue == null) {

                throw new IllegalStateException("Surface does not exist!");

            }



            long frameNumber = mBlastBufferQueue.getLastAcquiredFrameNum() + 1;

            mBlastBufferQueue.mergeWithNextTransaction(transaction, frameNumber);

        }

    }

}