Maybe the kerning functions are not implemented yet? The LuaHarfBuzz projects list the full api and there are many kerning related functions:
https://github.com/ufyTeX/luaharfbuzz/blob/abe15fef9f2bbf9e68bc54c7057056bcd73032bb/status/full_api.txt In the file `done.txt` there are no kerning related function. https://github.com/ufyTeX/luaharfbuzz/blob/abe15fef9f2bbf9e68bc54c7057056bcd73032bb/status/done.txt But I’m not an expert in this field .... On 21.07.25 22:51, Keno Wehr via luatex wrote: > For a LuaLaTeX package I need to read the kerning values of certain character > pairs as they are defined by the current font. If the Node renderer is used, > I can use the following code, where first_node and second_node are glyph > nodes: > > local current_font = font.getfont(first_node.font) > local kern = 0 > if current_font and current_font.resources > and current_font.resources.sequences then > for _, t in ipairs(current_font.resources.sequences) do > if t.features and t.features.kern and t.steps and t.steps[1] > and t.steps[1].coverage and t.steps[1].coverage[first_node.char] > and t.steps[1].coverage[first_node.char][second_node.char] then > kern = t.steps[1].coverage[first_node.char][second_node.char] > end > end > end > > However, I cannot be sure that the Node renderer is used, it may be the case > that HarfBuzz is used. But with HarfBuzz the font structure is different and > the above code does not return the kerning value needed. HarfBuzz defines a C > function hb_font_glyph_h_kerning(), but this function does not have a Lua > equivalent (unlike others listed in section 13.1 of the LuaTeX manual). > > Could anyone tell me how to get the kerning values with HarfBuzz? Josef
