switch to lpeg based color expression matching

1 files changed, 27 insertions, 33 deletions

diff --git a/luaotfload-colors.lua b/luaotfload-colors.lua
index 58089dc..5be0a1f 100644
--- a/luaotfload-colors.lua
+++ b/luaotfload-colors.lua
@@ -23,41 +23,37 @@ local registerotffeature    = otffeatures.register
 
 local add_color_callback --[[ this used to be a global‽ ]]
 
-local lpeg = require"lpeg"
-local lpegmatch = lpeg.match
+--[[doc--
+Color string validator / parser.
+--doc]]--
+
+local lpeg           = require"lpeg"
+local lpegmatch      = lpeg.match
 local C, Cg, Ct, P, R, S = lpeg.C, lpeg.Cg, lpeg.Ct, lpeg.P, lpeg.R, lpeg.S
 
-local digit16   = R("09", "af", "AF")
-local octet     = C(digit16 * digit16)
-local p_rgb     = Cg(octet, "red")
-                * Cg(octet, "green")
-                * Cg(octet, "blue")
-local p_rgba    = p_rgb * Cg(octet, "alpha")
-local p_color   = Ct(p_rgba + p_rgb)
-
-local old_sanitize_color_expression = function (value)
-    local sanitized
-    if value then
-        value = tostring(value)
-        local n_value = #value
-        if n_value == 6 or n_value == 8 then
-            sanitized = value
-        elseif n_value == 7 then --> take first six bytes
-            _, _, sanitized = stringsub(value, 1, 6)
-        elseif n_value > 8 then  --> take first eight bytes
-            _, _, sanitized = stringsub(value, 1, 8)
-        else
-            -- broken color code ignored, issue a warning?
-            luaotfload.warning(
-                "“%s” is not a valid rgb[a] color expression", value)
-        end
-    end
-    return sanitized
-end
+local digit16        = R("09", "af", "AF")
+local octet          = C(digit16 * digit16)
+
+local p_rgb          = octet * octet * octet
+local p_rgba         = p_rgb * octet
+local valid_digits   = C(p_rgba + p_rgb) -- matches eight or six hex digits
+
+local p_Crgb         = Cg(octet, "red") --- for captures
+                     * Cg(octet, "green")
+                     * Cg(octet, "blue")
+local p_Crgba        = p_Crgb * Cg(octet, "alpha")
+local extract_color  = Ct(p_Crgba + p_Crgb)
 
+--- string -> (string | nil)
 local sanitize_color_expression = function (digits)
-    local old = old_sanitize_color_expression(digits)
-    return old
+    digits = tostring(digits)
+    local sanitized = lpegmatch(valid_digits, digits)
+    if not sanitized then
+        luaotfload.warning(
+            "“%s” is not a valid rgb[a] color expression", digits)
+        return nil
+    end
+    return sanitized
 end
 
 --[[doc--
@@ -71,8 +67,6 @@ end
 ---         value)
 ---
 local function setcolor (tfmdata, value)
-    print("~~~~~~~~~~~~~")
-    print(value)
     local sanitized  = sanitize_color_expression(value)
     local properties = tfmdata.properties