On 12/10/2018 4:26 PM, mf wrote:
Hello list, i noticed that setting a different kerning breaks some features of opentype fonts; that is true, for example, for ligatures and fractions (frac feature).
It looks like a modified kerning inserts something between two adjacent character, making them no more adjacent. That way the lookup of opentype tables fails.
"f", "l" => "fl" ligature glyph
"f", [kerning], "l" => distinct "f" and "l" glyphs
"1", "/", "4" => "¼" glyph (with "frac" feature switched on)
"1", [kerning], "/", [kerning], "4" => distinct "1", "/", "4" glyphs (always with "frac" feature switched on)
MWE:
\definecharacterkerning[narrow][factor=-.015] \definecharacterkerning[wide][factor=.015]
\definefontfeature[frac][frac=yes]
\starttext \feature[+][frac]% Some ligatures: float, finance, affine; a fraction: 1/4.
\setcharacterkerning[narrow]Some ligatures: float, finance, affine; a fraction: 1/4.
\setcharacterkerning[wide]Some ligatures: float, finance, affine; a fraction: 1/4.
\stoptext
In my XML to PDF workflow, fractions are marked up, so it's easy to switch the kerning off only for them.
Instead i have no solution for ligatures: parts of text with a modified kerning loose ligatures, and i end up with the same words, once with ligatures, once without, even in the same page. Is there a workaround for this? character kerning is bad anyway ... say that we have:
effe and this is e ff e you definitely don't want to kern like e kern ff kern ff but e kern f kern f kern e so, ligatures are pretty useless with intercharacter kerning (as per definecharacterning) ... just conceptually incomatible (it is possible to turn it on but it really isnot what you want) ----------------------------------------------------------------- Hans Hagen | PRAGMA ADE Ridderstraat 27 | 8061 GH Hasselt | The Netherlands tel: 038 477 53 69 | www.pragma-ade.nl | www.pragma-pod.nl -----------------------------------------------------------------