SurfaceFlinger: fix early latching of buffers

Use the FrameTimeline::SurfaceFrame predicted present time
to avoid latching a buffer too early (i.e. before the time
SurfaceFlinger planned to latch this buffer when the app requested
a vsync callback).

Bug: 169901895
Test: expand notification shade and observe systrace
Change-Id: I823546992c89f88c0c29b839ce21c79ff1ffcfbd

1 files changed, 15 insertions, 0 deletions

diff --git a/services/surfaceflinger/BufferQueueLayer.cpp b/services/surfaceflinger/BufferQueueLayer.cpp
index 56d874258e..e8e31db236 100644
--- a/services/surfaceflinger/BufferQueueLayer.cpp
+++ b/services/surfaceflinger/BufferQueueLayer.cpp
@@ -222,6 +222,21 @@ bool BufferQueueLayer::hasFrameUpdate() const {
     return mQueuedFrames > 0;
 }
 
+nsecs_t BufferQueueLayer::nextPredictedPresentTime() const {
+    Mutex::Autolock lock(mQueueItemLock);
+    if (mQueueItems.empty()) {
+        return 0;
+    }
+
+    const auto& bufferData = mQueueItems[0];
+
+    if (!bufferData.item.mIsAutoTimestamp || !bufferData.surfaceFrame) {
+        return 0;
+    }
+
+    return bufferData.surfaceFrame->getPredictions().presentTime;
+}
+
 status_t BufferQueueLayer::updateTexImage(bool& recomputeVisibleRegions, nsecs_t latchTime,
                                           nsecs_t expectedPresentTime) {
     // This boolean is used to make sure that SurfaceFlinger's shadow copy