I was able to achieve a 21:9 resolution (2560x1080) by manually editing the System.ini file which you mentioned before.

This however uncovered another problem - the Field Of View.

Without adjusting the FOV, changing resultion from 4:3 is counterproductive - you actually see less of the game world than in 4:3. An adjustment is needed. This can be done in-game with "fov x" or in the User.ini file (see attached files).

The correct fovs are as follows:

4:3 - 90

16:9 - 106.2

16:10 - 100.3

21:9 - 121.1

I think it wouldn't hurt to automatically add this correction to the presets in you wrapper. I imagine playing the game with a wrong FOV for the given aspect ratio could be a different experience than it should.

Thanks for posting your findings; this is very interesting. So it seems that the widescreen fix is partially the cause of the issue, in that it has issues when set to resolutions above 1920x1200 (which is my display resolution/what I had it set to when I played through the game... I didn't think the crosshair & fonts were too small though).

The next time I update the wrapper I'll add a warning about not setting it above 1920x1200. Also I'll add an option to the menu for setting the FOV and will see about having it automatically set the initial resolution based on either matching the full resolution up to 1920x1200 or the aspect ratio if it's greater than that.

I strongly suggest to follow my advice of keeping the ingame res to 1280x720 for 16:9 (the actuall resolution of the 3D world will still be whatever set in nGlide). It's possible you didn't think that the crosshair or font is to small because you got used to it and played it on a bigger screen. Some people that wear glasses and people playing on smaller screens (example: laptop) could have a dramatically different experience. Besides that, the game was clearly not designed to play with a dot sized crosshair and tiny ammo amount indicator (which is hard to read even on my 23,8 inch screen, so imagine what will happen on a 1080p laptop). The default widescreen setting should be optimal and closest to the intended look of the game.

You don't need to detect resolution. The nGlide adjusts the resolution. The ingame res settings only influence the aspect ratio and the font/crosshair size. Giving presets like the below is enough:

16:9 - in-game res 1280x720; User.ini FOV - 106.2 ; nGlide res "By Destop", Aspect Ratio: Preserve original. (this one should be default)

16:10 - in-game res 1280x800; User.ini FOV - 100.3 ; nGlide res "By Destop", Aspect Ratio: Preserve original.

21:9 - in-game res 1280x540; User.ini FOV - 121.1 ; nGlide res "By Destop", Aspect Ratio: Preserve original.

4.3 - in-game res 1280x1024; User.ini FOV - 90 ; nGlide res "By Destop", Aspect Ratio: Preserve original.

Creating an additional res detection script for this specific game (and possibly for many nGlide games with similar interface problems) will be overdoing it, can negatively alter the experience for many users, and may simply cause problems like it did before.

There's nothing stopping people from simply changing it according to their preference if they find it too small; there will be information about it in the release notes.

As for resolution detection, that is part of the wrapper framework & I'm going to need to rework it a bit anyway (because from what I've learned here using the desktop resolution is unreliable for multi-monitor setups; unfortunately I don't have such a setup myself to test with and they don't seem to be all that common).

Resolution setting is a bit more specific, but since this uses plain text files for its configuration it's easy enough to do. Same for setting the FOV (which I've already created a menu option for).

Well, there is also nothing stopping people from changing it according to their preference if they find it too big (which is far less likely. as it's hard to find someone complaining that something is easier to read). This was also the intended look, which is an equally strong argument in my opinion. However, the decision is obviously ultimately yours and yours only - even if I may find it a little bit odd - and I'll stop suggesting it:)

I won't agree that dual monitor setups are uncommon, though. It may be uncommon in selected groups of people, but almost a default config in others (thus, this is an auto-epistemic fallacy). Most professional programmers and artists, generally game developers I know use dual monitor setups, and basically every one of them is a person that started their adventure with games in the 90's or early 2000's (thus, the main target of gog). They use the home PC for productivity and gaming alike.

As for the detection script, I suggest not using xrandr -q.

Use xrandr | grep -w connected | awk -F'[ \+]' '{print $1,$3,$4}' instead.

You get this at my machine:

HDMI-A-0 primary 2560x1440
DisplayPort-1 1920x1080 2560

The Primary Display is what we are aiming for.

Well, I'll think about it - there are other changes I need to make anyway (as well as some other projects I'm working on atm) so it'll probably be a while before I release the update.

I already started work on making the scripts use the primary display resolution last night :)

I've got similar issue with displaced screen; sometimes there was also no mouse control in main menu. It's exactly the same problem I always get when running under POL/Wine. No idea what was the reason, because such issue appears a day after the game worked perfectly fine. For now I solved the problem using:
./start.sh play desktop=1366x768
but I'm not sure it really worked or I've just got some random effect.