I've suggested this before on the Discord, but I've talked about this before, and I know stuff like this can get forgotten easily, so it's probably a good idea to suggest it here.

Currently, the windowed resolutions list in JJ2+ doesn't include the highest-resolution 16:9 resolution possible, 800x450. This resolution is possible in fullscreen mode if you set your graphics card settings to specifically include it as a mode, but you can't do this in windowed mode at the moment.

This makes a lot of sense. Intuitively I want to suggest the game should read the list of windowed resolutions from the list of fullscreen resolutions, rather than have them be hardcoded, but I welcome people to point out reasons that would be a bad idea.

It should also be quite easy to add this feature to a jazz2.exe on one's own with a hex editor, while waiting for the next JJ2+ to come around. I'll post instructions later if no one beats me to it.

Originally Posted by Violet CLM

This makes a lot of sense. Intuitively I want to suggest the game should read the list of windowed resolutions from the list of fullscreen resolutions, rather than have them be hardcoded, but I welcome people to point out reasons that would be a bad idea.

If the windowed resolutions were solely read from the fullscreen resolutions list, I would worry about some graphics cards potentially having issues with a lot of the lower-res sizes, so you might then not be able to play at windowed 320x200, for instance.

I don't suppose it would be possible for it to do both, would it? Like, read from the fullscreen ones, but then force several particular ones to also show up?... Maybe that's a bit silly.

That's a good point. There are also sometimes circumstances when the game doesn't load any fullscreen resolutions at all, either because you ask it to via command line arguments or because graphics cards are weird.

Let's talk hex editors! If you're even the least bit unsure of what you're doing, make a backup of your file first. In either case you're going to be opening Jazz2.exe and overwriting a series of four bytes with the hex sequence 20 03 C2 01.
In 1.23, overwrite the four bytes at 0xD3824.
In 1.24, overwrite the four bytes at 0xD16B0.
You should know you have the right place if the four bytes are all zeroes and they follow the sequence 20 03 58 02. Make sure you are overwriting, not inserting: the file should not change size.

This will be available in 5.8.