[Feature Request] Doom 64 support

[kenbot]

Doom 64 is not as popular as Ultimate Doom & Doom II, but there is still a Doomworld modding community around it. A handful of Doom 64 mods have won Cacowards, like Dreamblood https://www.doomworld.com/forum/topic/144234-wip-dreamblood-64-dreams-for-doom-64-episode-1-updated-v12/

Let's support it in Doom Launcher!

This should be surprisingly straightforward; you can already do this in DoomLauncher, sort of:

• Register your Doom64_x64.exe from Steam as a source port
• Register Doom64.wad from Steam as an IWAD. It will complain about it not being a proper IWAD, but ignore that. It doesn't have a proper title or thumbnail, because Doom64 WADs are a bit different.
• Load the mod (eg Dreamblood) into DoomLauncher in the usual way
• Run it with the Doom64 source port and Doom64 IWAD
• Steam will load up, it will give you an ARE YOU SURE? scare prompt about the extra parameters given the the EXE file, and away you go!

How:

• Improve IWAD parsing to recognise Doom64 WAD structure, so we can have good thumbnails and titles
• Make it so that it recognises Doom64 IWAD as a legit IWAD
• Fix the automatic Steam loader so that it automatically finds the Doom64 exe & wad
• Put a button in some menu to do a Steam check, so it's not just new users that can do it I think
• You can apparently get Doom64 on GOG as well; so we could either be happy with users manually adding it as a "source port", or have a separate menu option for "Add Doom64" so it's not just relying on the Steam loader

[kenbot]

Ohhh.... -iwad is not a thing for Doom 64. The exe file already knows how to find doom64.wad, and you can choose, say Doom2 as an IWAD in DoomLauncher and Doom64 will ignore it and run fine.

Probably best that Doom64 gets treated as its own thing then, separate from Source Ports and IWADs.

[kenbot]

It's a bit more interesting than I thought!

Doom64 mods are sometimes just a WAD file with a properly formatted text file, but sometimes they come with BAT files to install / uninstall the mod. The BATs don't all work the same, but they often replace doom64.kpf with a different file to allow patches, then replace it again with the original file in the UNINSTALL.BAT.

For example, while you can run the Dreamblood mod in DoomLauncher, it won't show the Dreamblood title or background images. If you run the BAT files that swap in the right KPF file, it will.

Good support for Doom64 probably requires a software implementation of the BAT file - I think directly running random BAT files from the internet is unacceptable, and the code in them is pretty simple.