[vlc-devel] [PATCH]: fix a CoInitializeEx() issue on Windows
remi at remlab.net
Tue Jul 16 20:22:04 CEST 2019
Le perjantaina 12. heinäkuuta 2019, 15.52.45 EEST Steve Lhomme a écrit :
> On 2019-07-12 14:32, Thomas Guillem wrote:
> > Hello,
> > OK for me.
> > Steve ?
> I think you meant Hugo who's the one who has been playing with that.
> Anyway it seems correct. The CoInitializeEx() calls in our Qt code uses
I don't think it's that simple.
If you create a COM object in the process' multi-thread apartment (MTA), then
you can only access it from a thread that is currently bound to the MTA.
If you create a COM object in a given thread's single-thread apartment (STA)
then you can only access it from _that_ thread while it remains bound to
its STA. That is why it is called "single thread" apartment.
So if you want to access a COM object from the Qt UI's STA-bound thread, you
must have created it on the Qt UI's thread. As such, I don't think changing
the vout display's threading model would fix anything; it would rather break
even more things.
 invoke a function in the object's COM vtable.
Ultimately, the problem is that no conventions were defined in VLC for how to
deal with COM, notably:
1) Can core functions and callbacks be invoked from an STA-bound thread, or
can functions and callbacks assume that binding the MTA will succeed, or
neither? (but not both)
2) Can core functions and callbacks be invoked from an MTA-bound thread, or
can functions and callbacks assume that instantiating an STA will succeed, or
neither? (but also not both)
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