SurfaceFlinger: expose vsync id extra buffers
Expose a function for clients to call and query the number
of extra buffers needed when vsync id is passed with the buffer.
Test: launch an app and observe systrace
Test: SF unit tests
Bug: 178148035
Change-Id: Icbeec66073feeae9768f0dcc45831b26144ab6f6
diff --git a/libs/gui/include/gui/ISurfaceComposer.h b/libs/gui/include/gui/ISurfaceComposer.h
index 81ff6b0..e56670d 100644
--- a/libs/gui/include/gui/ISurfaceComposer.h
+++ b/libs/gui/include/gui/ISurfaceComposer.h
@@ -508,6 +508,24 @@
* Gets priority of the RenderEngine in SurfaceFlinger.
*/
virtual int getGPUContextPriority() = 0;
+
+ /**
+ * Gets the extra buffers a client would need to allocate if it passes
+ * the Choreographer#getVsyncId with its buffers.
+ *
+ * When Choreographer#getVsyncId is passed to SurfaceFlinger, it is used
+ * as an indication of when to latch the buffer. SurfaceFlinger will make
+ * sure that it will give the app at least the time configured as the
+ * 'appDuration' before trying to latch the buffer.
+ *
+ * The total buffers needed for a given configuration is basically the
+ * numbers of vsyncs a single buffer is used across the stack. For the default
+ * configuration a buffer is held ~1 vsync by the app, ~1 vsync by SurfaceFlinger
+ * and 1 vsync by the display. The extra buffers are calculated as the
+ * number of additional buffers on top of the 3 buffers already allocated
+ * by the app.
+ */
+ virtual status_t getExtraBufferCount(int* extraBuffers) const = 0;
};
// ----------------------------------------------------------------------------
@@ -570,6 +588,7 @@
SET_FRAME_TIMELINE_INFO,
ADD_TRANSACTION_TRACE_LISTENER,
GET_GPU_CONTEXT_PRIORITY,
+ GET_EXTRA_BUFFER_COUNT,
// Always append new enum to the end.
};