The history of luaTEX 2006–2009 / v 0.50 - Pragma ADE

local function hyphenation(head,tail)
return head, tail, lang.hyphenate(head,tail) -- returns done
end
local function ligaturing(head,tail)
return node.ligaturing(head,tail) -- returns head,tail,done
end
local function kerning(head,tail)
return node.kerning(head,tail) -- returns head,tail,done
end
filters.add(hyphenation)
filters.add(ligaturing)
filters.add(kerning)
callback.register("pre_linebreak_filter", run_filters)
callback.register("hpack_filter", run_filters)
Although one can inject extra lters by using the add function it may be clear that this
can be dangerous due to interference. Therefore a slightly more secure variant is the
following, where main is reserved for macro package actions and the others can be used
by add--ons.
filters = { } -- global namespace
local list = {
pre = { }, main = { }, post = { },
}
local order = {
"pre", "main", "post"
}
local function somewhere(where)
if not where then
texio.write_nl("error: invalid filter category")
elseif not list[where] then
texio.write_nl(string.format("error: invalid filter category
'%s'",where))
else
return list[where]
end
return false
274 The order of things