Question regarding compositing

[Leon Henrik Plickat]

Hi!

I have an x8r8g8b8 mask, a solid fill colour source and an a8r8g8b8
desitnation image. The mask contains rasterized glyphs (using
https://codeberg.org/dnkl/fcft). The destination image is fully
transparent, meaning completely filled with 0x00000000. I now want to
composite the glyph into the destination image using the colour source.

I have tried using pixman_image_composite32(), however I either get no
results (the destination image stays fully transparent, at least
visually), or I get a black box around the glyph (the glyph itself
appears as expected, however the entire area of the mask is no longer
transparent), depending on the operator.

Clearly I am doing something wrong / am missing some crucial bit of
information. So what would be the correct way to composite the glyph
from the mask into the transparent destination image, in a certain
colour?

Any pointers appreciated!

-- 
Friendly Greetings,
Leon Henrik Plickat