diff options
| -rw-r--r-- | luaotfload-extralibs.lua | 35 |
1 files changed, 33 insertions, 2 deletions
diff --git a/luaotfload-extralibs.lua b/luaotfload-extralibs.lua index 6d486b2..21f738c 100644 --- a/luaotfload-extralibs.lua +++ b/luaotfload-extralibs.lua @@ -411,14 +411,45 @@ end --- feature mechanism otffeatures.register { - name = "letterspace", --"kerncharacters", - description = "letterspace", --"kerncharacters", + name = "kernfactor", + description = "kernfactor", initializers = { base = initializefontkerning, node = initializefontkerning, } } +--[[doc-- + + The “letterspace” feature is essentially identical with the above + “kernfactor” method, but scales the factor to percentages to match + Xetex’s behavior. (See the Xetex reference, page 5, section 1.2.2.) + + Since Xetex doesn’t appear to have a (documented) “max” keyword, we + assume all input values are numeric. + +--doc]]-- + +local initializecompatfontkerning = function (tfmdata, percentage) + local factor = tonumber (percentage) + if not factor then + logs.names_report ("both", 0, "letterspace", + "Invalid argument to letterspace: %s (type %q), was expecting percentage as Lua number instead.", + percentage, type (percentage)) + return + end + return initializefontkerning (tfmdata, factor * 0.01) +end + +otffeatures.register { + name = "letterspace", + description = "letterspace", + initializers = { + base = initializecompatfontkerning, + node = initializecompatfontkerning, + } +} + kerns.set = nil local characterkerning_enabled = false |