On Wed, 26 Jul 2023 21:14:07 GMT, Alexey Ivanov <aiva...@openjdk.org> wrote:
>>> Probably… But it is still incorrect. Initialising COM on a thread doesn't >>> mean you can call COM object methods from any thread in your application. >> >> Note that "Objects created on a COM thread in a multithread apartment (MTA) >> must be able to receive method calls from other threads at any time", so if >> we initialisethe devices on one thread using COM they will be avaliable on >> other threads as well. But the spec for DirectSoundEnumerate says nothing >> about COM... But from some examples I see ppl wrap it by the >> CoInitializeEx(NULL, COINIT_MULTITHREADED)/CoUninitialize(); >> >> Not sure we can call CoInitializeEx on the main thread. > >> > Probably… But it is still incorrect. Initialising COM on a thread doesn't >> > mean you can call COM object methods from any thread in your application. >> >> Note that "Objects created on a COM thread in a multithread apartment (MTA) >> must be able to receive method calls from other threads at any time", so if >> we initialisethe devices on one thread using COM they will be avaliable on >> other threads as well. > > But from the threads where you initialised COM as MTA. > > The docs for `CoInitializeEx` clearly state you have to initialise COM before > you can use it. Thus, calling methods of COM objects from an arbitrary thread > in your application is wrong, isn't it? > >> But the spec for DirectSoundEnumerate says nothing about COM... But from >> some examples I see ppl wrap it by the CoInitializeEx(NULL, >> COINIT_MULTITHREADED)/CoUninitialize(); >> >> Noe sure we can call CoInitializeEx on the main thread. > > It's for any thread not only the main thread… You can all > `AudioSystem.getMixerInfo` from any thread in a Java app, if > `DirectSoundEnumerate` needs COM to be initialised even though the > documentation doesn't mention it, we have to initalise COM. Thus there are > two options: > > 1. Call `CoInitializeEx`, enumerate devices, and call `CoUninitialize`. > 2. Create an executor service which initialises COM on its worker thread, > enumerate devices on the worker thread and return the devices. The worker > thread may terminate (after it calls `CoUninitialize`) if it doesn't receive > more requests in a period of time. > > > 3. Do another CoInitialize before call :- not a good approach > > > > Yet it does not break the rules: you can initialise COM, call an API and > > then call > > [`CoUninitialize`](https://learn.microsoft.com/en-us/windows/win32/api/combaseapi/nf-combaseapi-couninitialize). > > If you don't keep any references to COM objects, it is valid. > > Tried this approach and it works, we may need to do the similar approach for > another function `DAUDIO_GetDirectAudioDeviceDescription` because this also > calling `DirectSoundEnumerateW `& `DirectSoundCaptureEnumerateW ` Does this approach return full names for devices, without truncating them? ------------- PR Review Comment: https://git.openjdk.org/jdk/pull/14898#discussion_r1275491546
