[PATCH v2 1/2] mf: Specify a user queue for presentation clock callbacks.

[Conor McCarthy]

From: Conor McCarthy

Calling MFScheduleWorkItemEx() schedules the operation in the timer
queue, but callback invocation occurs in the standard queue. Execution
of app callbacks in a dedicated thread prevents possible slow execution
from competing with demuxing and decoding. This matches native Windows
behaviour.
---
 dlls/mf/clock.c | 17 ++++++++++++++++-
 1 file changed, 16 insertions(+), 1 deletion(-)

diff --git a/dlls/mf/clock.c b/dlls/mf/clock.c
index e6be05d2794..1fd6b3028a0 100644
--- a/dlls/mf/clock.c
+++ b/dlls/mf/clock.c
@@ -1054,9 +1054,24 @@ static ULONG WINAPI present_clock_sink_callback_Release(IMFAsyncCallback *iface)
     return IMFPresentationClock_Release(&clock->IMFPresentationClock_iface);
 }

+static DWORD mf_get_sink_queue_id(void)
+{
+    static SRWLOCK mf_sink_queue_srw = SRWLOCK_INIT;
+    static DWORD mf_sink_queue_id;
+
+    AcquireSRWLockExclusive(&mf_sink_queue_srw);
+    if (!mf_sink_queue_id)
+        MFAllocateWorkQueue(&mf_sink_queue_id);
+    ReleaseSRWLockExclusive(&mf_sink_queue_srw);
+
+    return mf_sink_queue_id ? mf_sink_queue_id : MFASYNC_CALLBACK_QUEUE_STANDARD;
+}
+
 static HRESULT WINAPI present_clock_callback_GetParameters(IMFAsyncCallback *iface, DWORD *flags, DWORD *queue)
 {
-    return E_NOTIMPL;
+    *flags = 0;
+    *queue = mf_get_sink_queue_id();
+    return S_OK;
 }

static HRESULT WINAPI present_clock_sink_callback_Invoke(IMFAsyncCallback *iface, IMFAsyncResult *result)