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
diff --git a/libs/gui/BLASTBufferQueue.cpp b/libs/gui/BLASTBufferQueue.cpp
index 0a3d44d..4904955 100644
--- a/libs/gui/BLASTBufferQueue.cpp
+++ b/libs/gui/BLASTBufferQueue.cpp
@@ -146,6 +146,10 @@
mTransformHint = mSurfaceControl->getTransformHint();
mBufferItemConsumer->setTransformHint(mTransformHint);
+ SurfaceComposerClient::Transaction()
+ .setFlags(surface, layer_state_t::eEnableBackpressure,
+ layer_state_t::eEnableBackpressure)
+ .apply();
mNumAcquired = 0;
mNumFrameAvailable = 0;
@@ -169,13 +173,20 @@
void BLASTBufferQueue::update(const sp<SurfaceControl>& surface, uint32_t width, uint32_t height,
int32_t format) {
std::unique_lock _lock{mMutex};
- mSurfaceControl = surface;
-
if (mFormat != format) {
mFormat = format;
mBufferItemConsumer->setDefaultBufferFormat(format);
}
+ SurfaceComposerClient::Transaction t;
+ bool applyTransaction = false;
+ if (!SurfaceControl::isSameSurface(mSurfaceControl, surface)) {
+ mSurfaceControl = surface;
+ t.setFlags(mSurfaceControl, layer_state_t::eEnableBackpressure,
+ layer_state_t::eEnableBackpressure);
+ applyTransaction = true;
+ }
+
ui::Size newSize(width, height);
if (mRequestedSize != newSize) {
mRequestedSize.set(newSize);
@@ -184,13 +195,15 @@
// If the buffer supports scaling, update the frame immediately since the client may
// want to scale the existing buffer to the new size.
mSize = mRequestedSize;
- SurfaceComposerClient::Transaction t;
t.setFrame(mSurfaceControl,
{0, 0, static_cast<int32_t>(mSize.width),
static_cast<int32_t>(mSize.height)});
- t.apply();
+ applyTransaction = true;
}
}
+ if (applyTransaction) {
+ t.apply();
+ }
}
static void transactionCallbackThunk(void* context, nsecs_t latchTime,
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);
diff --git a/libs/gui/SurfaceComposerClient.cpp b/libs/gui/SurfaceComposerClient.cpp
index 78f655a..96c099b 100644
--- a/libs/gui/SurfaceComposerClient.cpp
+++ b/libs/gui/SurfaceComposerClient.cpp
@@ -934,7 +934,8 @@
return *this;
}
if ((mask & layer_state_t::eLayerOpaque) || (mask & layer_state_t::eLayerHidden) ||
- (mask & layer_state_t::eLayerSecure) || (mask & layer_state_t::eLayerSkipScreenshot)) {
+ (mask & layer_state_t::eLayerSecure) || (mask & layer_state_t::eLayerSkipScreenshot) ||
+ (mask & layer_state_t::eEnableBackpressure)) {
s->what |= layer_state_t::eFlagsChanged;
}
s->flags &= ~mask;
diff --git a/libs/gui/include/gui/LayerState.h b/libs/gui/include/gui/LayerState.h
index 83a9d33..b1305c6 100644
--- a/libs/gui/include/gui/LayerState.h
+++ b/libs/gui/include/gui/LayerState.h
@@ -82,6 +82,10 @@
eLayerOpaque = 0x02, // SURFACE_OPAQUE
eLayerSkipScreenshot = 0x40, // SKIP_SCREENSHOT
eLayerSecure = 0x80, // SECURE
+ // Queue up BufferStateLayer buffers instead of dropping the oldest buffer when this flag is
+ // set. This blocks the client until all the buffers have been presented. If the buffers
+ // have presentation timestamps, then we may drop buffers.
+ eEnableBackpressure = 0x100, // ENABLE_BACKPRESSURE
};
enum {
@@ -157,8 +161,8 @@
uint32_t h;
uint32_t layerStack;
float alpha;
- uint8_t flags;
- uint8_t mask;
+ uint32_t flags;
+ uint32_t mask;
uint8_t reserved;
matrix22_t matrix;
Rect crop_legacy;