Optimize menubar.icon_theme.lookup_icon: do not look twice

lib/menubar/icon_theme.lua

@@ -147,6 +147,7 @@ local directory_size_distance = function(self, subdirectory, icon_size)
 end
 
 local lookup_icon = function(self, icon_name, icon_size)
+    local checked_already = {}
     for _, subdir in ipairs(self.index_theme:get_subdirectories()) do
         for _, basedir in ipairs(self.base_directories) do
             for _, ext in ipairs(self.extensions) do
@@ -156,6 +157,8 @@ local lookup_icon = function(self, icon_name, icon_size)
                                                    icon_name, ext)
                     if awful.util.file_readable(filename) then
                         return filename
+                    else
+                        checked_already[filename] = true
                     end
                 end
             end
@@ -170,6 +173,7 @@ local lookup_icon = function(self, icon_name, icon_size)
                 local filename = string.format("%s/%s/%s/%s.%s",
                                                basedir, self.icon_theme_name, subdir,
                                                icon_name, ext)
+                if not checked_already[filename] then
                     local dist = directory_size_distance(self, subdir, icon_size)
                     if awful.util.file_readable(filename) and  dist < minimal_size then
                         closest_filename = filename
@@ -178,11 +182,8 @@ local lookup_icon = function(self, icon_name, icon_size)
                 end
             end
         end
-    if closest_filename then
-        return closest_filename
     end
-
+    return closest_filename
-    return nil
 end
 
 local find_icon_path_helper  -- Gets called recursively.