Add configuration option to call CoInitializeEx with COINIT_APARTMENTTHREADED flag

[tim-depthkit]

Required Info
Camera Model	N/A
Firmware Version	N/A
Operating System & Version	Win (8.1/10)
Kernel Version (Linux Only)
Platform	PC
SDK Version	2.20.0 and up
Language	C
Segment	VR/AR

Issue Description

Currently the WMF backend initialized COM as follows: CoInitializeEx(nullptr, COINIT_MULTITHREADED); // when using COINIT_APARTMENTTHREADED, calling _pISensor->SetEventSink(NULL) to stop sensor can take several seconds

However in applications that have COM initializations on other threads using COINIT_APARTMENTTHREADED (like the Qt framework, for example), this can lead to a deadlock inside COM functions.

As the comment suggests, there is a reason for initializing in this way, but the SDK user should be allowed to configure this if necessary, via a CMake build option or similar.

[dorodnic]

Yep, that make sense. Do you think this can be covered as a CMake parameter or dedicated API?

[tim-depthkit]

A CMake option would be sufficient for my use case.

On Wed, Jun 19, 2019 at 7:50 AM Sergey Dorodnicov notifications@github.com wrote:

Yep, that make sense. Do you think this can be covered as a CMake parameter or dedicated API?

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[RealSenseCustomerSupport]

---

We are planning on implementing this. The rough schedule is Q3. Thanks.

[RealSenseSupport]

The change has been merged into the development branch. Please let us know if there is any concerns. Thank you.

[RealSenseSupport]

This enhancement is included in the v2.40.0 release. Thank you. Release Notes and search for DSO-15197 Closing this case.

[kayychou]

Hi @tim-depthkit, @dorodnic,

I encounter issues using the Qt framework after initializing my Intel camera D415 so reading these posts is really helpful to understand the root cause.

My issue (Main-UI blocked when opening a QFileDialog) seems to be solved by using librealsense compiled with the cmake option COM_MULTITHREADED set to OFF.

Could you please give me more insights regarding the impact this option can have on the SDK behaviour ? The doc mentions that "stop sensor can take several seconds". @tim-depthkit Have you noticed unwanted side effects with the option COM_MULTITHREADED set to OFF ? @RealSenseCustomerSupport to what extent do you recommend to preferably use the SDK with this option set to ON ?

Thanks for your support!

[MartyG-RealSense]

Hi @kayychou The only available RealSense related reference to COM_MULTITHREADED is a line in the lrs_options CMake file that provides for COM_MULTITHREADED the description "Set OFF to initialize COM library with COINIT_APARTMENTTHREADED". It is set to On by default.

https://github.com/IntelRealSense/librealsense/blob/master/CMake/lrs_options.cmake#L8C27-L8C90

A Microsoft reference at the link below suggests that COINT_APARTMENTTHREADED should be used (i.e set to On) when there is a thread that creates a window. So you could interpret that to mean that when COM_MULTITHREADED is set to Off, COINT_APARTMENTTHREADED is On, which is useful in a thread that needs to create a window.

https://learn.microsoft.com/en-us/windows/win32/learnwin32/initializing-the-com-library