if you downloaded the source from github you would have a folder called font if you look in side you will see that there is packer.c, unpacker.c and editor.c.
1) copy font.h from /includes and paste it into /font.
2) compile the editor, unpacker and packer i am not sure how one would do this on windows but on linux it would just be make editor unpacker packer
3) open cmd prompt/terminal and change the directory to /The-Powder-Toy and run linux: ./unpacker >> font.bin windows: not sure it might be similar to linux
4) you would now have a file called font.bin it is a file that /font that is what is needed to run the editor with the current icons tpt use.
5) run the editor via cmd/terminal and then press space/backspace to find an empty character, it may be a thermometer if it is just erase it via right clicking and left clicking in the drawing field. now draw you character and look in cmd/terminal and the last number you will see there is the char id and it corresponds to what icon you drew.
6) close down the editor and delete the font.h then run: linux: ./packer >> font.h windows : not sure
7) copy the new font.h into /includes replacing the old one.
8) for your new menu set the char id to what i told you to remember before. etc: {"\xFF", "new menu ftw", 0, 1}, FF is the char id.
9) recompile and you should be ready to go.
edit: added this to the wiki and simon added information about windows
I asked about this back, you'll have to find my thread, where, for reference, I listed the icon types. The '\x(Hexedecimal number)' controls the images
@ForumTroll(View Post) It looks like a new wiki page was just created that explains how to do this on linux and windows. You need to use command prompt. Maybe I should try using it to create custom icons for my mod, but i'm not very artistic/creative.
I just tried it, and it didn't work for me either. It didn't recoginze the command gcc or something. I also tried using visual studio command prompt and got the same error. After creating a visual studio project and changing some stuff, I got it to compile though. It's too complicated to explain what I did, so I just put the exe's on github here. The font is already unpacked, so you can just start by running editor.exe. When you are done, run packer.exe. You don't need to use command prompt, it will just output to stdout.txt and you can copy it all into font.h from there.