feat: Make Tied DSKs visible in Preview

[djordje-mancic]

When enabling "Tie" for a downstream key, it would be helpful to have the DSK show on the Preview display while in Studio mode, since most modern video switchers function this way.
Another possibility would be to make this a togglable option on a per-DSK basis.

[exeldro]

At the moment I don't know any OBS API that allows me to do that. So it would require changes in OBS itself to make it possible.

[dunronet]

While the OBS API does not permit overlaying DSK onto the Preview, I've been exploring a workaround by creating a "dummy" scene that is wiped out and then re-assembled on every scene/DSK item change. The dummy scene can be shown in a projector window.

The drawbacks are:

• potential memory leaks, particularly when using websocket vendor and/or changing scenes/dsk items quickly
• • previewing the dummy scene directly would also make things unstable, plus there's a risk of the end-user adding the dummy scene to a DSK...
• the projector window isn't in the same window as OBS (i.e. isn't in a dock) -- I have another program that allows me to keep it always on top.

The amount of "user-mistake proofing" needed to avoid such memory leaks was why I tossed out this idea originally... but the lack of a true preview is such a thorn in our side that I'm close to risking it.

Screen shot of my initial attempt below... it's from a church service context (although I have very old overlays loaded on my personal machine)

@djordje-mancic I would love to hear if this would fit what you're trying to achieve.

[djordje-mancic]

@dunronet Yes, that's exactly something I would like to achieve, except with it being visible inside of the OBS window as well as the multiview. It's a really a shame that the OBS API doesn't have a feature similar to output channels but for preview instead of program only.
My guess is that it would be best to implement preview channels inside of the OBS API itself, making it easy to implement this feature into the DSK plugin afterwards.