Pay attention to buffer timestamps
When acquiring a buffer, SurfaceFlinger now computes the expected
presentation time and passes it to the BufferQueue acquireBuffer()
method. If it's not yet time to display the buffer, acquireBuffer()
returns PRESENT_LATER instead of a buffer.
The current implementation of the expected-present-time computation
uses approximations and guesswork.
Bug 7900302
Change-Id: If9345611c5983a11a811935aaf27d6388a5036f1
diff --git a/include/gui/BufferQueue.h b/include/gui/BufferQueue.h
index 766fa0f..0143be3 100644
--- a/include/gui/BufferQueue.h
+++ b/include/gui/BufferQueue.h
@@ -39,7 +39,7 @@
enum { NUM_BUFFER_SLOTS = 32 };
enum { NO_CONNECTED_API = 0 };
enum { INVALID_BUFFER_SLOT = -1 };
- enum { STALE_BUFFER_SLOT = 1, NO_BUFFER_AVAILABLE };
+ enum { STALE_BUFFER_SLOT = 1, NO_BUFFER_AVAILABLE, PRESENT_LATER };
// When in async mode we reserve two slots in order to guarantee that the
// producer and consumer can run asynchronously.
@@ -284,7 +284,13 @@
// acquired then the BufferItem::mGraphicBuffer field of buffer is set to
// NULL and it is assumed that the consumer still holds a reference to the
// buffer.
- status_t acquireBuffer(BufferItem *buffer);
+ //
+ // If presentWhen is nonzero, it indicates the time when the buffer will
+ // be displayed on screen. If the buffer's timestamp is farther in the
+ // future, the buffer won't be acquired, and PRESENT_LATER will be
+ // returned. The presentation time is in nanoseconds, and the time base
+ // is CLOCK_MONOTONIC.
+ status_t acquireBuffer(BufferItem *buffer, nsecs_t presentWhen);
// releaseBuffer releases a buffer slot from the consumer back to the
// BufferQueue. This may be done while the buffer's contents are still