commit f6eddb6b42a9548f1298e899ea06a7a042182783
author Vishnu Nair <vishnun@google.com> Wed Jan 27 22:02:11 2021 -0800
committer Vishnu Nair <vishnun@google.com> Thu Jan 28 11:54:57 2021 -0800
tree 3c3cfcc5c4589cc80069a25de8a362f7f5434599
parent dd5bfa93b0c6633b7372c87fc8d7a83a73a5cd1c

Enable backpressure for BufferStateLayer

The default behaviour of buffer state layer is to drop older
buffers if there are newer buffers that are ready to be presented.

When emulating BufferQueue behavior via the adapter, we want
to queue up buffers without any present timestamps. To solve this,
we introduce a layer state flag to keep the buffer in the transaction
queue if there is already a buffer that is ready to be applied.

Test: atest SurfaceViewBufferTests:BufferPresentationTests
Bug: 176967609
Change-Id: I33f6347bd1c7a2d80dc4214e596bb864abe8c6bf

libs/gui/LayerState.cpp

diff --git a/libs/gui/LayerState.cpp b/libs/gui/LayerState.cpp
index e5e10a0..2946aae 100644
--- a/libs/gui/LayerState.cpp
+++ b/libs/gui/LayerState.cpp
@@ -183,12 +183,9 @@
     SAFE_PARCEL(input.readUint32, &layerStack);
     SAFE_PARCEL(input.readFloat, &alpha);
 
-    uint32_t tmpUint32 = 0;
-    SAFE_PARCEL(input.readUint32, &tmpUint32);
-    flags = static_cast<uint8_t>(tmpUint32);
+    SAFE_PARCEL(input.readUint32, &flags);
 
-    SAFE_PARCEL(input.readUint32, &tmpUint32);
-    mask = static_cast<uint8_t>(tmpUint32);
+    SAFE_PARCEL(input.readUint32, &mask);
 
     SAFE_PARCEL(matrix.read, input);
     SAFE_PARCEL(input.read, crop_legacy);
@@ -229,6 +226,7 @@
         SAFE_PARCEL(input.read, *acquireFence);
     }
 
+    uint32_t tmpUint32 = 0;
     SAFE_PARCEL(input.readUint32, &tmpUint32);
     dataspace = static_cast<ui::Dataspace>(tmpUint32);