Issue with applying kerning from this font

[schombert]

I am attempting to render text using the https://github.com/adobe-fonts/source-serif font via harfbuzz (with the smcp feature turned on), but it doesn't seem handle the kerning correctly. Prior to switching to harfbuzz, I was rendering text via freetype and manually getting kerning data out of the gpos table. This produced the following result, which I have confirmed with the font's creator is the intended result

This, however, is what I am currently getting via harfbuzz shaping and positioning glyphs according to the values in hb_buffer_get_glyph_positions

As you can see, the kerning between the small caps A and small caps V doesn't seem to have been correctly applied. Is there a reference renderer or something along those lines that I can use to help verify whether this is an issue in my code or whether it really is a harfbuzz problem?

[behdad]

Is there a reference renderer or something along those lines that I can use to help verify whether this is an issue in my code or whether it really is a harfbuzz problem?

Are you passing HB_SCRIPT_LATIN to HarfBuzz?

The reference renderers is hb-view. Also useful to inspect output of hb-shape.

[schombert]

I switched everything to a hard-coded

hb_buffer_set_direction(hb_buf, HB_DIRECTION_LTR);
hb_buffer_set_script(hb_buf, HB_SCRIPT_LATIN);
hb_buffer_set_language(hb_buf, hb_language_from_string("en", -1));

and the kerning issue persists

[schombert]

Also, is there a way to turn on smcp for hb-view and hb-shape? without that, I won't be able to check the issue.

[behdad]

Also, is there a way to turn on smcp for hb-view and hb-shape? without that, I won't be able to check the issue.

--features smcp.

[schombert]

Ok, so after rendering it with hb-view, the kerning shows up correctly. So it is definitely something wrong I am doing; I just have no idea what

[behdad]

How are you opening the face? Is this with hb-ft or something?

[schombert]

via this

FT_New_Memory_Face(ft_library, fnt.file_data.get(), file_size, 0, &fnt.font_face);
FT_Select_Charmap(fnt.font_face, FT_ENCODING_UNICODE);
FT_Set_Pixel_Sizes(fnt.font_face, 0, dr_size);
fnt.hb_font_face = hb_ft_font_create(fnt.font_face, nullptr);
hb_font_set_scale(fnt.hb_font_face, dr_size, dr_size);

[behdad]

The problem is probably with dr_size. Try multiplying it by 64.

[behdad]

Or. Not call set_scale at all.

[schombert]

without set scale we get

which appears correct to me
Thank you so much for your time!

[behdad]

Looks good. Glad it worked out.