DosFreak said:
It is possible. In fact there's a patch somewhere on the forum, I haven't checked it out in a long time but IIRC it requires having to manually synchronize the guest with the host.
Here's a link to that patch-
Vertical retrace sync patch
I was sort of laughing to myself as I added the manual calibration. I couldn't find a way to reliably read the retrace status in a cross-platform way.. then momentarily considered using a webcam or something unusual.. and then decided that the combination of the users' eyes plus keyboard is cross-platform (you likely have a keyboard.. and if you care about vsync, you've got eyes). I apologize for that, as it is rather silly.
The patch got applied to at least one unofficial build, but it wasn't fully functional because it requires two keys (to tweak period and offset) to be made available, but this apparently wasn't done for that build. (I think I made a bad typo in one of my posts and said F8 twice instead of F9 or something..). Anyway, if you want to apply this patch yourself, I wish you luck 😀. I've been meaning to come back to it at some point and do a proper patch that automatically syncs perfectly on Windows.. and then in theory someone who is more familiar with other platforms would take a liking to it after playing a silky smooth game of pinball or two, and find a way to make it crossplatform. I should have done that in the first place.
Here's another thread in which I talked about the issues a bit as I was beginning to implement it (could potentially waste a bit of your time reading it, as there is a lot of text):
Screen tearing in DOS games running through DOSBox
As for Dark Forces in particular.. I remember someone mentioning that the game Tie Fighter always had a lot of shearing and there's nothing you can do about it. I believe both Dark Forces and Tie Fighter were developed by Lucasarts, so I wonder if the developers of both shared similar ideas about screen updates (perhaps Dark Forces is another game that shears, with nothing you can do about it).