Empty rendering output under windows

[kleinsimon]

Hi tomolt,

Thanks for this library. I'm trying to use it under windows, but I always get an unmodified bitmap, regardless what I do. I used the latest tag 10.2 as well as the current main.

I compiled it with gcc (mingw64) and tested it with the demo from https://github.com/lhf/libschrift-show :

gcc -c -o schrift.o schrift.c
gcc -o schrift.dll -s -shared schrift.o -Wl,--subsystem,windows
gcc -o show.exe show.c -I./ -L./ -lschrift

The program then runs fine, I tried it with different fonts like arial etc, but the resulting image is always plain white. The same happens when I use the library from my own program. One thing I noticed is that populating the image struct with anything other than 0 results in an error. Is this intended?