TextureView/GLES20Canvas: Support synchronous GLConsumers

Always update to the newest available frame from a GLConsumer.
Otherwise, with a synchronous queue, rendering can fall behind and
eventually deadlock with producer.

Bug: 10830400
Change-Id: I7f1d752c80ae5dac892a26d82e86806c27f5d955

1 files changed, 17 insertions, 0 deletions

diff --git a/core/jni/android_view_GLES20Canvas.cpp b/core/jni/android_view_GLES20Canvas.cpp
index dc90da7..b720e73 100644
--- a/core/jni/android_view_GLES20Canvas.cpp
+++ b/core/jni/android_view_GLES20Canvas.cpp
@@ -878,6 +878,23 @@ static void android_view_GLES20Canvas_updateTextureLayer(JNIEnv* env, jobject cl
     sp<GLConsumer> surfaceTexture(SurfaceTexture_getSurfaceTexture(env, surface));
 
     if (surfaceTexture->updateTexImage() == NO_ERROR) {
+        int64_t frameNumber = surfaceTexture->getFrameNumber();
+        // If the GLConsumer queue is in synchronous mode, need to discard all
+        // but latest frame, using the frame number to tell when we no longer
+        // have newer frames to target. Since we can't tell which mode it is in,
+        // do this unconditionally.
+        int dropCounter = 0;
+        while (surfaceTexture->updateTexImage() == NO_ERROR) {
+            int64_t newFrameNumber = surfaceTexture->getFrameNumber();
+            if (newFrameNumber == frameNumber) break;
+            frameNumber = newFrameNumber;
+            dropCounter++;
+        }
+        #if DEBUG_RENDERER
+        if (dropCounter > 0) {
+            RENDERER_LOGD("Dropped %d frames on texture layer update", dropCounter);
+        }
+        #endif
         surfaceTexture->getTransformMatrix(transform);
         GLenum renderTarget = surfaceTexture->getCurrentTextureTarget();