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-rw-r--r--luaotfload-extralibs.lua35
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