surface_control.h: Clarify callback documentation

In response to API council feedback we more clearly
document the differences between the OnCommit and the
OnComplete callbacks.

Fixes: 187846583
Test: Doc changes only
Change-Id: Ib0529d7d01de046ccae8f14c8bf8bb9a6110624d

1 files changed, 10 insertions, 0 deletions

diff --git a/include/android/surface_control.h b/include/android/surface_control.h
index f6c2e55c2d..644efd9afa 100644
--- a/include/android/surface_control.h
+++ b/include/android/surface_control.h
@@ -133,6 +133,9 @@ typedef struct ASurfaceTransactionStats ASurfaceTransactionStats;
  * ASurfaceTransaction_OnComplete callback can be used to be notified when a frame
  * including the updates in a transaction was presented.
  *
+ * Buffers which are replaced or removed from the scene in the transaction invoking
+ * this callback may be reused after this point.
+ *
  * \param context Optional context provided by the client that is passed into
  * the callback.
  *
@@ -153,6 +156,13 @@ typedef void (*ASurfaceTransaction_OnComplete)(void* context, ASurfaceTransactio
  * are ready to be presented. This callback will be invoked before the
  * ASurfaceTransaction_OnComplete callback.
  *
+ * This callback does not mean buffers have been released! It simply means that any new
+ * transactions applied will not overwrite the transaction for which we are receiving
+ * a callback and instead will be included in the next frame. If you are trying to avoid
+ * dropping frames (overwriting transactions), and unable to use timestamps (Which provide
+ * a more efficient solution), then this method provides a method to pace your transaction
+ * application.
+ *
  * \param context Optional context provided by the client that is passed into the callback.
  *
  * \param stats Opaque handle that can be passed to ASurfaceTransactionStats functions to query