Correctly pass screenshot fences to transaction callbacks
In some instances, a screenshot may be captured before a layer has a
release callback registered. This can happen when a new buffer has
not yet been transacted before a screenshot is captured. This causes the
screenshot fence to be dropped and the possibility of tearing when
capturing a screenshot while continuously rendering.
To resolve this, buffer screenshot fences into a list of future fences
when there is no callback registered, and merge those fences when
dispatching the release callback.
Bug: 302703346
Test: SurfaceViewTests#testMovingWhiteSurfaceView 100 times
Change-Id: I91aec3cdb0973092d48cd77e59dd3999e9d9e847
diff --git a/services/surfaceflinger/SurfaceFlinger.cpp b/services/surfaceflinger/SurfaceFlinger.cpp
index 51a11e2..7626fe7 100644
--- a/services/surfaceflinger/SurfaceFlinger.cpp
+++ b/services/surfaceflinger/SurfaceFlinger.cpp
@@ -8152,14 +8152,23 @@
: ftl::yield(present()).share();
for (auto& [layer, layerFE] : layers) {
- layer->onLayerDisplayed(ftl::Future(presentFuture)
- .then([layerFE = std::move(layerFE)](FenceResult) {
- return layerFE->stealCompositionResult()
- .releaseFences.back()
- .first.get();
- })
- .share(),
- ui::INVALID_LAYER_STACK);
+ layer->onLayerDisplayed(presentFuture, ui::INVALID_LAYER_STACK,
+ [layerFE = std::move(layerFE)](FenceResult) {
+ if (FlagManager::getInstance()
+ .screenshot_fence_preservation()) {
+ const auto compositionResult =
+ layerFE->stealCompositionResult();
+ const auto& fences = compositionResult.releaseFences;
+ // CompositionEngine may choose to cull layers that
+ // aren't visible, so pass a non-fence.
+ return fences.empty() ? Fence::NO_FENCE
+ : fences.back().first.get();
+ } else {
+ return layerFE->stealCompositionResult()
+ .releaseFences.back()
+ .first.get();
+ }
+ });
}
return presentFuture;