1 files changed, 78 insertions, 0 deletions
diff --git a/tex/context/base/mkiv/font-prv.lua b/tex/context/base/mkiv/font-prv.lua
new file mode 100644
index 000000000..20c06d2e5
--- /dev/null
+++ b/tex/context/base/mkiv/font-prv.lua
@@ -0,0 +1,78 @@
+if not modules then modules = { } end modules ['font-prv'] = {
+    version   = 1.001,
+    comment   = "companion to font-ini.mkiv and hand-ini.mkiv",
+    author    = "Hans Hagen, PRAGMA-ADE, Hasselt NL",
+    copyright = "PRAGMA ADE / ConTeXt Development Team",
+    license   = "see context related readme files"
+}
+
+local type = type
+local formatters = string.formatters
+
+local fonts             = fonts
+local helpers           = fonts.helpers
+local fontdata          = fonts.hashes.identifiers
+
+local setmetatableindex = table.setmetatableindex
+
+local currentprivate    = fonts.privateoffsets.textextrabase
+local maximumprivate    = currentprivate + 0xFFF
+
+local extraprivates     = { }
+helpers.extraprivates   = extraprivates
+
+function fonts.helpers.addextraprivate(name,f)
+    extraprivates[#extraprivates+1] = { name, f }
+end
+
+-- if we run out of space we can think of another range but by sharing we can
+-- use these privates for mechanisms like alignments-on-character and such
+
+local sharedprivates = setmetatableindex(function(t,k)
+    local v = currentprivate
+    if currentprivate < maximumprivate then
+        currentprivate = currentprivate + 1
+    else
+        -- reuse last slot, todo: warning
+    end
+    t[k] = v
+    return v
+end)
+
+function helpers.addprivate(tfmdata,name,characterdata)
+    local properties = tfmdata.properties
+    local characters = tfmdata.characters
+    local privates   = properties.privates
+    if not privates then
+        privates = { }
+        properties.privates = privates
+    end
+    if not name then
+        name = formatters["anonymous_private_0x%05X"](currentprivate)
+    end
+    local usedprivate = sharedprivates[name]
+    privates[name] = usedprivate
+    characters[usedprivate] = characterdata
+    return usedprivate
+end
+
+function helpers.getprivates(tfmdata)
+    if type(tfmdata) == "number" then
+        tfmdata = fontdata[tfmdata]
+    end
+    local properties = tfmdata.properties
+    return properties and properties.privates
+end
+
+function helpers.hasprivate(tfmdata,name)
+    if type(tfmdata) == "number" then
+        tfmdata = fontdata[tfmdata]
+    end
+    local properties = tfmdata.properties
+    local privates = properties and properties.privates
+    return privates and privates[name] or false
+end
+
+function helpers.privateslot(name)
+    return rawget(sharedprivates,name)
+end