[PATCH 0/1] MR4133: mfmediaengine: Don't send event notify when engine is shutdown.

[PATCH 1/1] mfmediaengine: Don't send event notify when engine is shutdown.

[Yuxuan Shui]

From: Yuxuan Shui

I've also tried saving a cancel cookie from `BeginCreateObject*` and using it to cancel the
operation in engine shutdown. However there are 2 problems:

1. Callback might still get called after `CancelObjectCreation`. Microsoft's
     [own documentation](https://learn.microsoft.com/en-us/windows/win32/api/mfidl/nf-mfidl-imfsource...)
     says as much:
       > Because these methods are asynchronous, however, they might be completed before the
       > operation can be canceled. Therefore, your callback might still be invoked after you
       > call this method.
  2. Our implementations of `BeginCreateObject*` are not cancellable. They call either
     `MFPutWorkItem` or `IMFByteStream_BeginRead`, neight of which provides cancellation.
     (and our `CancelObjectCreation` doesn't actually work. AsyncResult objects aren't added to
     `handler->results` list until they are completed, which means any attempts to cancel an
     yet-to-be-completed object creation will always fail with `MF_E_UNEXPECTED`)
---
 dlls/mfmediaengine/main.c | 20 ++++++++++++++------
 1 file changed, 14 insertions(+), 6 deletions(-)

diff --git a/dlls/mfmediaengine/main.c b/dlls/mfmediaengine/main.c
index 5a63974967d..77c7b2bd745 100644
--- a/dlls/mfmediaengine/main.c
+++ b/dlls/mfmediaengine/main.c
@@ -1356,12 +1356,6 @@ static HRESULT WINAPI media_engine_load_handler_Invoke(IMFAsyncCallback *iface,

EnterCriticalSection(&engine->cs);

-    engine->network_state = MF_MEDIA_ENGINE_NETWORK_LOADING;
-    IMFMediaEngineNotify_EventNotify(engine->callback, MF_MEDIA_ENGINE_EVENT_LOADSTART, 0, 0);
-
-    start_playback = engine->flags & FLAGS_ENGINE_PLAY_PENDING;
-    media_engine_set_flag(engine, FLAGS_ENGINE_SOURCE_PENDING | FLAGS_ENGINE_PLAY_PENDING, FALSE);
-
     if (SUCCEEDED(IMFAsyncResult_GetState(result, &state)))
     {
         hr = IMFSourceResolver_EndCreateObjectFromByteStream(engine->resolver, result, &obj_type, &object);
@@ -1373,6 +1367,20 @@ static HRESULT WINAPI media_engine_load_handler_Invoke(IMFAsyncCallback *iface,
     if (FAILED(hr))
         WARN("Failed to create source object, hr %#lx.\n", hr);

+    if (engine->flags & FLAGS_ENGINE_SHUT_DOWN)
+    {
+        LeaveCriticalSection(&engine->cs);
+        TRACE("Engine is shut down, stopping...\n");
+        IUnknown_Release(object);
+        return S_OK;
+    }
+
+    engine->network_state = MF_MEDIA_ENGINE_NETWORK_LOADING;
+    IMFMediaEngineNotify_EventNotify(engine->callback, MF_MEDIA_ENGINE_EVENT_LOADSTART, 0, 0);
+
+    start_playback = engine->flags & FLAGS_ENGINE_PLAY_PENDING;
+    media_engine_set_flag(engine, FLAGS_ENGINE_SOURCE_PENDING | FLAGS_ENGINE_PLAY_PENDING, FALSE);
+
     if (object)
     {
         if (SUCCEEDED(hr = IUnknown_QueryInterface(object, &IID_IMFMediaSource, (void **)&source)))

[Nikolay Sivov (＠nsivov)]

According to my experiments with media extension instance, I don't think there is a need to call EndCreate*() if the engine was shut down. What we'll need to do instead is to release the resolver/extension on Shutdown() as well, as a separate fix. This also implies that on Invoke() you'll have nothing to call EndCreate* on.

Cancellation call is also not used with the extension, so I don't think it's a requirement to cancel it.