1 files changed, 74 insertions, 0 deletions
diff --git a/tex/context/base/mkiv/typo-lan.lua b/tex/context/base/mkiv/typo-lan.lua
new file mode 100644
index 000000000..c42d2119e
--- /dev/null
+++ b/tex/context/base/mkiv/typo-lan.lua
@@ -0,0 +1,74 @@
+if not modules then modules = { } end modules ['typo-lan'] = {
+    version   = 1.001,
+    comment   = "companion to typo-lan.mkiv",
+    author    = "Hans Hagen, PRAGMA-ADE, Hasselt NL",
+    copyright = "PRAGMA ADE / ConTeXt Development Team",
+    license   = "see context related readme files"
+}
+
+local type, next = type, next
+
+local currentfont       = font.current
+local setmetatableindex = table.setmetatableindex
+local utfbyte           = utf.byte
+
+local hashes            = fonts.hashes
+local fontdata          = hashes.characters
+local emwidths          = hashes.emwidths
+
+local frequencies       = languages.frequencies or { }
+languages.frequencies   = frequencies
+
+local frequencydata     = { }
+local frequencyfile     = string.formatters["lang-frq-%s.lua"]
+local frequencycache    = { }
+
+setmetatableindex(frequencydata, function(t,language)
+    local fullname = resolvers.findfile(frequencyfile(language))
+    local v = fullname ~= "" and dofile(fullname)
+    if not v or not v.frequencies then
+        v = t.en
+    end
+    t[language] = v
+    return v
+end)
+
+setmetatableindex(frequencycache, function(t,language)
+    local dataset = frequencydata[language]
+    local frequencies = dataset.frequencies
+    if not frequencies then
+        return t.en
+    end
+    local v = { }
+    setmetatableindex(v, function(t,font)
+        local average = emwidths[font] / 2
+        if frequencies then
+            local characters = fontdata[font]
+            local sum, tot = 0, 0
+            for k, v in next, frequencies do
+                local character = characters[k] -- characters[type(k) == "number" and k or utfbyte(k)]
+                tot = tot + v
+                sum = sum + v * (character and character.width or average)
+            end
+            average = sum / tot -- widths
+        end
+        t[font] = average
+        return average
+    end)
+    t[language] = v
+    return v
+end)
+
+function frequencies.getdata(language)
+    return frequencydata[language]
+end
+
+function frequencies.averagecharwidth(language,font)
+    return frequencycache[language or "en"][font or currentfont()]
+end
+
+interfaces.implement {
+    name      = "averagecharwidth",
+    actions   = { frequencies.averagecharwidth, context },
+    arguments = "string"
+}