gears.color: Add much more sophiscated stuff

Signed-off-by: Uli Schlachter <psychon@znc.in>

lib/gears/color.lua.in

@@ -9,15 +9,27 @@ local string = string
 local table = table
 local tonumber = tonumber
 local unpack = unpack
+local pairs = pairs
+local type = type
+local capi = {
+    oocairo = oocairo
+}
 
 module("gears.color")
 
+--- Parse a HTML-color.
+-- This function can parse colors like #rrggbb and #rrggbbaa.
+-- For example, parse_color("#00ff00ff") would return 0, 1, 0, 1.
 -- Thanks to #lua for this. :)
-
+-- @param col The color to parse
+-- @return 4 values which each are in the range [0, 1].
 function parse_color(col)
     local rgb = {}
     for pair in string.gmatch(col, "[^#].") do
-        table.insert(rgb, tonumber(pair, 16) / 255)
+        local i = tonumber(pair, 16)
+        if i then
+            table.insert(rgb, i / 255)
+        end
     end
     while #rgb < 4 do
         table.insert(rgb, 1)
@@ -25,6 +37,117 @@ function parse_color(col)
     return unpack(rgb)
 end
 
-setmetatable(_M, { __call = function (_, ...) return parse_color(...) end })
+--- Find all numbers in a string
+-- @param s The string to parse
+-- @return Each number found as a separate value
+local function parse_numbers(s)
+    local res = {}
+    for k in string.gmatch(s, "-?[0-9]+[.]?[0-9]*") do
+        table.insert(res, tonumber(k))
+    end
+    return unpack(res)
+end
+
+--- Create a solid pattern
+-- @param col The color for the pattern
+-- @return A cairo pattern object
+function create_solid_pattern(col)
+    local col = col
+    if col == nil then
+        col = "#000000"
+    end
+    return capi.oocairo.pattern_create_rgba(parse_color(col))
+end
+
+--- Create an image pattern from a png file
+-- @param file The filename of the file
+-- @return a cairo pattern object
+function create_png_pattern(file)
+    local image = capi.oocairo.image_surface_create_from_png(file)
+    return capi.oocairo.pattern_create_for_surface(image)
+end
+
+--- Add stops to the given pattern.
+-- @param p The cairo pattern to add stops to
+-- @param iterator An iterator that returns strings. Each of those strings
+--                 should be in the form place,color where place is in [0, 1].
+function add_stops(p, iterator)
+    for k in iterator do
+        local sub = string.gmatch(k, "[^,]+")
+        local point, color = sub(), sub()
+        p:add_color_stop_rgba(point, parse_color(color))
+    end
+end
+
+--- Create a linear pattern object.
+-- The pattern is created from a string. This string should have the following
+-- form: "x0,y0:x1,y1:<stops>"
+-- x0,y0 and x1,y1 are the start and stop point of the pattern.
+-- For the explanation of "<stops>", see add_stops().
+-- @param arg The argument describing the pattern
+-- @return a cairo pattern object
+-- @nname create_linear_pattern
+-- @nclass function
+
+--- Create a radial pattern object.
+-- The pattern is created from a string. This string should have the following
+-- form: "x0,y0,r0:x1,y1,r1:<stops>"
+-- x0,y0 and x1,y1 are the start and stop point of the pattern.
+-- r0 and r1 are the radii of the start / stop circle.
+-- For the explanation of "<stops>", see add_stops().
+-- @param arg The argument describing the pattern
+-- @return a cairo pattern object
+-- @nname create_radial_pattern
+-- @nclass function
+
+for k, v in pairs({ linear = capi.oocairo.pattern_create_linear,
+                    radial = capi.oocairo.pattern_create_radial}) do
+    _M["create_" .. k .. "_pattern"] = function(arg)
+        local iterator = string.gmatch(arg, "[^:]+")
+        -- Create a table where each entry is a number from the original string
+        local args = { parse_numbers(iterator()) }
+        local to = { parse_numbers(iterator()) }
+        -- Now merge those two tables
+        for k, v in pairs(to) do
+            table.insert(args, v)
+        end
+        -- And call our creator function with the values
+        local p = v(unpack(args))
+
+        add_stops(p, iterator)
+        return p
+    end
+end
+
+types = {
+    solid = create_solid_pattern,
+    png = create_png_pattern,
+    linear = create_linear_pattern,
+    radial = create_radial_pattern
+}
+
+--- Create a pattern from a given string.
+-- This function can create solid, linear, radial and png patterns. In general,
+-- patterns are specified as "type:arguments". "arguments" is specific to the
+-- pattern used. For example, one can use
+-- "linear:50,50,10:55,55,30:0,#ff0000:0.5,#00ff00:1,#0000ff"
+-- Any argument that cannot be understood is passed to create_solid_pattern().
+-- @see create_solid_pattern, create_png_pattern, create_linear_pattern,
+--      create_radial_pattern
+-- @param col The string describing the pattern.
+-- @return a cairo pattern object
+function create_pattern(col)
+    if type(col) == "string" then
+        local t = string.match(col, "[^:]+")
+        if types[t] then
+            local pos = string.len(t)
+            local arg = string.sub(col, pos + 2)
+            return types[t](arg)
+        end
+    end
+    return create_solid_pattern(col)
+end
+
+setmetatable(_M, { __call = function (_, ...) return create_pattern(...) end })
 
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