On Wed, 26 Jul 2023 21:16:11 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 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? But if that code requare com my expectation would be that they call CoInitialize/CoUninitialize. This CoInitialize initially was added here https://bugs.openjdk.org/browse/JDK-6950553 (check the stack trace), https://github.com/openjdk/jdk/commit/b8b9c35567919f9f375cc3610d823524cf5b8582 can we check that the DAUDIO_GetDirectAudioDeviceDescription is really uses that com object w/o initialisation? >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. We can try reuse the "Filechooser.invokeCom" machinery, but I do not think I like it. ------------- PR Review Comment: https://git.openjdk.org/jdk/pull/14898#discussion_r1275574660
