gears.color: Add a way to bypass the pattern cache

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

lib/gears/color.lua.in

@@ -170,6 +170,36 @@ color.types = {
     radial = color.create_radial_pattern
 }
 
+--- Create a pattern from a given string.
+-- For full documentation of this function, please refer to create_pattern().
+-- This difference between create_pattern() and this function is that this
+-- function does not insert the generated objects into the pattern cache. Thus,
+-- you are allowed to modify the returned object.
+-- @see create_pattern
+-- @param col The string describing the pattern.
+-- @return a cairo pattern object
+function color.create_pattern_uncached(col)
+    -- If it already is a cairo pattern, just leave it as that
+    if cairo.Pattern:is_type_of(col) then
+        return col
+    end
+    local col = col or "#000000"
+    if type(col) == "string" then
+        local t = string.match(col, "[^:]+")
+        if color.types[t] then
+            local pos = string.len(t)
+            local arg = string.sub(col, pos + 2)
+            return color.types[t](arg)
+        end
+    elseif type(col) == "table" then
+        local t = col.type
+        if color.types[t] then
+            return color.types[t](col)
+        end
+    end
+    return color.create_solid_pattern(col)
+end
+
 --- Create a pattern from a given string.
 -- This function can create solid, linear, radial and png patterns. In general,
 -- patterns are specified as strings formatted as"type:arguments". "arguments"
@@ -180,8 +210,13 @@ color.types = {
 -- { type = "radial", from = { 50, 50, 10 }, to = { 55, 55, 30 },
 --   stops = { { 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
+--
+-- Please note that you MUST NOT modify the returned pattern, for example by
+-- calling :set_matrix() on it, because this function uses a cache and your
+-- changes could thus have unintended side effects. Use create_pattern_uncached
+-- if you need to modify the returned pattern.
+-- @see create_pattern_uncached, 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 color.create_pattern(col)
@@ -191,26 +226,10 @@ function color.create_pattern(col)
     end
     local col = col or "#000000"
     local result = pattern_cache[col]
-    if result then
-        return result
-    end
-    if type(col) == "string" then
-        local t = string.match(col, "[^:]+")
-        if color.types[t] then
-            local pos = string.len(t)
-            local arg = string.sub(col, pos + 2)
-            result = color.types[t](arg)
-        end
-    elseif type(col) == "table" then
-        local t = col.type
-        if color.types[t] then
-            result = color.types[t](col)
-        end
-    end
     if not result then
-        result = color.create_solid_pattern(col)
+        result = color.create_pattern_uncached(col)
+        pattern_cache[col] = result
     end
-    pattern_cache[col] = result
     return result
 end
 

spec/gears/color_spec.lua

@@ -151,17 +151,14 @@ describe("gears.color", function()
             end)
 
             it("with NONE repeat", function()
-                -- XXX: Can't use color() here because else the returned object
-                -- ends up in the pattern cache. What should we do about that?
-                local pattern = color.create_linear_pattern("0,0:0,10:0,#00ff00ff:1,#ff00ffff")
+                local pattern = color.create_pattern_uncached("linear:0,0:0,10:0,#00ff00ff:1,#ff00ffff")
                 pattern:set_extend("NONE")
                 assert.is_not.opaque(pattern)
             end)
         end)
 
         it("opaque linear pattern", function()
-            local pattern = color("linear:0,0:0,10:0,#00ff00ff:1,#ff00ffff")
-            assert.is.opaque(pattern)
+            assert.is.opaque("linear:0,0:0,10:0,#00ff00ff:1,#ff00ffff")
         end)
 
         it("opaque surface pattern", function()
@@ -196,6 +193,18 @@ describe("gears.color", function()
             pending("unsupported pattern type")
         end
     end)
+
+    describe("pattern cache", function()
+        it("caching works", function()
+            assert.is.equal(color("#00ff00"), color("#00ff00"))
+        end)
+
+        it("create_pattern_uncached does not cache", function()
+            -- Since tests run in order, the above test already inserted
+            -- "#00ff00" into the cache
+            assert.is_not.equal(color.create_pattern_uncached("#00ff00"), color.create_pattern_uncached("#00ff00"))
+        end)
+    end)
 end)
 
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