gromit-mpx not selectable as XCOMPOSITE source in OBS Studio

[Llammissar]

Is your feature request related to a problem? Please describe.
I want to try using gromit to do telestration for my streams, but OBS studio's Xcomposite capture plugin doesn't detect the annotation window. Since our Twitter discussion, I did some digging into the OBS source, and I'm still not sure whose bug it really ought to be (hence filing it as an FR), but here's what I have for now:

This appears to be the function OBS uses to find all the windows it can capture:
https://github.com/obsproject/obs-studio/blob/master/plugins/linux-capture/xcompcap-helper.cpp#L96

The important X11 details seem to be that it depends on Extended Window Manager Hints and that the window is in the _NET_CLIENT_LIST. I won't pretend to understand the GTK/GDK end of things, but given the scope of that list, my immediate question is if gromit doesn't get parented to the display's root window?

Describe the solution you'd like
At the least, I'd like for OBS to be able to detect and capture the gromit window so I can crop/align it onto my stream preview and composite them together.

Spitballing, a potentially-even-better solution (from my perspective, that is) would be if I could use "windowed gromit" so it only works in a particular window or region. Maybe even go the TransparentPaint route and put it in a WM-managed window that can be resized on the fly... that's probably way more work than is worth for a niche feature, admittedly

Describe alternatives you've considered
Currently, I get this functionality from dewdle, but it's an ugly hack involving nodejs, a browser, painstaking window alignment, and forcing my WM to render the window translucent so I can sort of see what I'm doing. The "nice" solution would put me out about $1000 USD for the NDI software, encoder, and windows machine to run it. Windows users can reach for TransparentPaint, but it's three years unmaintained and also WPF so I couldn't get it running in Wine. I am still considering attempting to write a native telestrator plugin for OBS.

[bk138]

Hi @Wyatts, thanks for reporting here. Can you provide me with a step-by-step description of a simple setup so I can repro?

Is it simply: installing OBS and trying to capture Gromit-MPX annotations? IIRC from twitter it's a bit more complicated...

Just tried OBS:

• with whole-screen capture (XSHM): captures annotations.
• with window-capture (XCOMPOSITE): does not capture annotations, which is expected as OBS just captures (the actually off-screen) contents of the selected window and Gromit-MPX's annotations are in another window.
• I reckon you're selecting multiple OBS sources with one being the Gromit-MPX window?

[bk138]

#75 might be related...

[Llammissar]

Yeah, that's almost my repro. The distinction is when I add an Xcomposite source, I don't even see gromit in the dropdown; it sounds like you do?

[bk138]

Yeah, that's almost my repro. The distinction is when I add an Xcomposite source, I don't even see gromit in the dropdown; it sounds like you do?

Me neither, and that's very likely due to https://github.com/bk138/gromit-mpx/blob/master/src/main.c#L1222

[yassir-a-p]

Hi, I just discovered Gromit MPX, it's really great. Though, I also searched for annotation tool because I want to use it in OBS to be used as separate source, not in whole-screen capture.
Hope this issue can be solved soon.

[flaviobarros]

Any news?

[veroarriola]

Hi. I just had the same issue.

[Pistos]

+1; please implement, if possible.

[nasafix-nasser]

Hi, I just have the same issue! Any news :(