Fix behavior of QAudioSink::resume in push mode

Up to now, a QAudioSink in push mode (ie. started without a QIODevice,
but returning a QIODevice buffer that the client has to push data into)
transitioned to IdleState when resuming after a suspend, even if there
was still data in the buffer or device to play. This resulted in the
sink playing audio even though it was in IdleState, and the client not
getting notified when the audio data was actually drained (as the
stateChanged signal did not get emitted again).

Fix this by storing the state in which the sink gets suspended, and
restore to that state when resuming. If the sink then runs into an
underrun because not enough data is available in the push-buffer, then
it will transition to IdleState with UnderrunError later.

Implement this consistently in all platform implementations, adjust the
test, which previously verified that a push-sink transitions to
IdleState when resuming, and change the documentation accordingly.

[ChangeLog][QtMutimedia][QAudioSink] Calling QAudioSink::resume() now
returns the sink to the state it had when QAudioSink::suspend() was
called, no matter whether the sink operates in pull or push mode.

Pick-to: 6.5
Change-Id: If0c7fe8629627de814276d629d825e469c998d2d
Reviewed-by: Lars Knoll <lars@knoll.priv.no>
Reviewed-by: Artem Dyomin <artem.dyomin@qt.io>

1 files changed, 3 insertions, 4 deletions

diff --git a/src/multimedia/audio/qaudiosink.cpp b/src/multimedia/audio/qaudiosink.cpp
index 5f38bbc98..47d522d2c 100644
--- a/src/multimedia/audio/qaudiosink.cpp
+++ b/src/multimedia/audio/qaudiosink.cpp
@@ -203,10 +203,9 @@ void QAudioSink::suspend()
 /*!
     Resumes processing audio data after a suspend().
 
-    Sets error() to QAudio::NoError.
-    Sets state() to QAudio::ActiveState if you previously called start(QIODevice*).
-    Sets state() to QAudio::IdleState if you previously called start().
-    emits stateChanged() signal.
+    Sets state() to the state the sink had when suspend() was called, and sets
+    error() to QAudioError::NoError. This function does nothing if the audio sink's
+    state is not QAudio::SuspendedState.
 */
 void QAudioSink::resume()
 {