Fonts do not sit correctly on baseline

[chrisridd]

I tried to draw a single line of text in multiple fonts, aligned at the baseline. The results are not great, using 40pt text just to make it a bit more obvious:

The red line is my baseline. I'm doing:

vst_alignment(handle, 0, 0, &dummy, &dummy); // left, baseline

vst_font(handle, fontid1);
vst_point(handle, 40, &dummy, &dummy, &dummy, &dummy);
v_ftext(handle, xstart, ystart, "DejaVu");

vst_font(handle, fontid2);
vst_point(handle, 40, &dummy, &dummy, &dummy, &dummy);
xstart += (width-of-DejaVu-text);
v_ftext(handle, xstart, ystart, "Bookerly");

vst_font(handle, fontid3);
vst_point(handle, 40, &dummy, &dummy, &dummy, &dummy);
xstart += (width-of-Bookerly-text);
v_ftext(handle, xstart, ystart, "Helvetica");

NVDI 5 does get the vertical alignment correct.

The ft2_text_render() assembles the character bitmaps into a bigger buffer and blits it to the screen using a vertical offset from extra.distance. The computation of the extra.distance fields seems to be OK, but the more I read about metrics and sizes at freetype.org the less I feel I know! Is the bbox the right way to measure things, or just the ascent+descent?

The errors are reasonably significant (up to 16 pixels in my screenshot!), so they can't be just simple rounding errors.

[chrisridd]

After the patch in #26 this is what I get:

[mfro0]

Looks better now for me as well. Thank you for your contribution!

[chrisridd]

Thanks! And it looks like moving a variable declaration down broke on an older compiler - apologies for that.