Improve capheight guessing a bit

We first check if the font have a non-zero os2_capheight and use it,
else we use the height of "X" glyph, else we set capheight to the font's
ascender. The later can be improved by checking certain glyphs in other
scripts (Greek, Cyrillic etc.)

1 files changed, 10 insertions, 8 deletions

diff --git a/luaotfload.dtx b/luaotfload.dtx
index 2be5db8..a593b4e 100644
--- a/luaotfload.dtx
+++ b/luaotfload.dtx
@@ -570,19 +570,21 @@ luaotfload.loadmodule('font-clr.lua')
 local function def_font(...)
     local fontdata = fonts.define.read(...)
     if fontdata then
+        local capheight
         local units     = fontdata.units
         local size      = fontdata.size
         local otfdata   = fontdata.shared.otfdata
 
-        local capheight = otfdata.pfminfo.os2_capheight
-
-        local dimen8 = capheight/units*size
-
-        if capheight <= 0 then
-            dimen8 = fontdata.characters[string.byte("X")].height
+        if otfdata.pfminfo.os2_capheight > 0 then
+            capheight = otfdata.pfminfo.os2_capheight/units*size
+        else
+            if fontdata.characters[string.byte("X")] then
+                capheight = fontdata.characters[string.byte("X")].height
+            else
+                capheight = otfdata.metadata.ascent/units*size
+            end
         end
-
-        fontdata.parameters[8] = dimen8
+        fontdata.parameters[8] = capheight
     end
     return fontdata
 end