stb_truetype: stbtt_GetPackedQuad doesn't seem to stick to baseline

[forksnd]

@nothings
I am trying out the new texture baking API by first baking the texture, and then dumping the texture and the stbtt_packedchar array in a file. This file gets loaded in another process that uses stbtt_GetPackedQuad to render the characters. When I do this, the characters don't stick to the baseline as can be seen in the image below.

The quad is created and rendered as shown in this example code. The font I am using is this one (the "Regular" variant).

Any idea what I might be doing wrong?

---

The basic code flow I am using is:

1. For baking:

   stbtt_InitFont();
   stbtt_PackBegin();
   stbtt_PackSetOversampling();
   stbtt_PackFontRanges(); // multiple times with different fontdata each time
   stbtt_PackEnd();
   fwrite(packedchar[]); // As a header file full of designated initializers (floats printed as hex using %a)
   fwrite(pixels); // As a header file containing an array of uint8_t (like xxd)

   Font size in stbtt_pack_range is set using the STBTT_POINT_SIZE macro.
2. For rendering:

   #include "pixels.h"
   #include "packedchar.h"
   stbtt_GetPackedQuad();
   render(quad);

[nothings]

Impossible to say without more info. The most likely issues would be in your code: either your packedchar printing code is wrong, or your render() code is wrong.

Obviously the first thing to do is to simplfy and eliminate variables. Run stbtt_ in the same process and make sure that works. Write out the packedchars to a binary file with fwrite not fprintf and make sure that works. If both of those work, then you've narrowed it down to your fprintf. If it fails in the earlier steps, you can diagnose why with fewer things to worry about.

[forksnd]

Thanks, just wanted to confirm that I am not missing a step, to maybe adjust the resulting quad with some font metrics or something. The entire code will be too complex to post here, I'll see what I can debug.

[nothings]

If you're calling stbtt_PackFontRanges multiple times, each call writes out stbtt_packedchar data, so you also need to make sure that's to separate arrays (or non-overlapping parts of the same array).

[forksnd]

Fixed! There were two issues:

1. The floats were getting cast to ints deep in the GPU pipeline. (I forgot that the previous font code dealt with pixel-coordinates)
2. I had set align_to_integer in stbtt_GetPackedQuad to true.

Removing the cast and setting align_to_integer to false seems to have fixed the issue.