Dohyun Kim wrote:
Considering current state that we don't know any fonts that has ITLC table,
it would be better than nothing to implement italic correction as follows.
In the following code, "fontdata" is a table returned by the function
"fonts.define.read".
local param = fontdata.parameters
local italicangle = fontdata.shared.otfdata.metadata.italicangle
if italicangle and italicangle < 0 then
local uwidth = fontdata.shared.otfdata.metadata.uwidth or 40
local factor = fontdata.factor or 655.36
param.slant = - math.tan(italicangle*math.pi/180) * param.quad
for i,v in pairs(fontdata.characters) do
local gl = fontdata.descriptions[i]
local it = (gl.boundingbox[3] - gl.width + uwidth*0.5) * factor
if it > 0 then v.italic = it end
end
end
there are seleveral solutions:
- extend the font with this info (faster but then it's always there
which might not be ok as it's an approximation)
- calculate it after loading (which is what you propose)
in the mkiv code we do have a hook for that kind of things so this is
then what i propose. watch how we don't scale here, we just add an entry
to the shared data as that's where we hook in; the real implementation
would look slightly different as an optimization is possible
\starttext
\startluacode
table.insert(fonts.triggers,"itlc")
local function itlc(tfmdata,value)
if value then
-- the magic 40 and it formula come from Dohyun Kim
local fontdata = tfmdata.shared.otfdata or tfmdata.shared.afmdata
local metadata = fontdata and fontdata.metadata
if metadata then
local italicangle = metadata.italicangle
if italicangle and italicangle ~= 0 then
local uwidth = (metadata.uwidth or 40)/2
for unicode, d in next, tfmdata.descriptions do
local it = d.boundingbox[3] - d.width + uwidth
if it ~= 0 then
d.italic = it
end
end
end
end
end
end
fonts.initializers.base.otf.itlc = itlc
fonts.initializers.node.otf.itlc = itlc
fonts.initializers.base.afm.itlc = itlc
fonts.initializers.node.afm.itlc = itlc
\stopluacode
\definedfont[SerifItalic*default at 24pt] test\/test
\definefontfeature[xdefault][default][itlc=yes]
\definedfont[SerifItalic*xdefault at 24pt] test\/test
\stoptext
i could add it to the generic code (although i'm not going to add all
the other context goodies to the generic code definitely not as long as
they're experimental)
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