Look for icons in all directories from the specification

According to Icon Theme Specification Version 0.11[1], "apps
should look [for icons] in $HOME/.icons (for backwards compatibility),
in $XDG_DATA_DIRS/icons and in /usr/share/pixmaps (in that order)."

Fix icon size handling. The assignment of icon_sizes to isizes in
the lookup_icon() function, is not necessary and caused the former
table to grow rapidly.

[1] http://standards.freedesktop.org/icon-theme-spec/icon-theme-spec-0.11.html

freedesktop/dirs.lua

@@ -0,0 +1,85 @@
+-- -*- lua-indent-level: 4; indent-tabs-mode: nil -*-
+-- Grab environment
+
+local string = string
+local io = io
+local os = os
+local table = table
+local type = type
+local ipairs = ipairs
+local pairs = pairs
+
+module("freedesktop.dirs")
+
+local _xdg_dirs = {}
+local _xdg_home = {}
+
+local xdg_default_dirs = {
+    DATA   = "/usr/local/share:/usr/share",
+    CONFIG = "/etc/xdg",
+}
+
+local xdg_default_home = {
+    CACHE  = ".cache/",
+    CONFIG = ".config/",
+    DATA   = ".local/share/",
+}
+
+local function xdg_dirs(d)
+    local env = os.getenv('XDG_' .. d .. '_DIRS')
+    local ret = {}
+    if not env or env == "" then
+        env = xdg_default_dirs[d]
+    end
+    for i in string.gmatch(env, "[^:]+") do
+        i = string.gsub(i,'/*$', '')
+        table.insert(ret, i .. '/')
+    end
+    _xdg_dirs[d] = ret
+    return ret
+end    
+
+function xdg_config_dirs()
+    if _xdg_dirs['CONFIG'] then
+        return _xdg_dirs['CONFIG']
+    end
+    return xdg_dirs('CONFIG')
+end
+
+function xdg_data_dirs()
+    if _xdg_dirs['DATA'] then
+        return _xdg_dirs['DATA']
+    end
+    return xdg_dirs("DATA")
+end
+
+local function xdg_home(d)
+    local ret = os.getenv('XDG_' .. d .. '_HOME')
+    if not ret or ret == "" then
+        local home = string.gsub(os.getenv('HOME'),'/*$', '')
+        ret = home .. '/' .. xdg_default_home[d]
+    end
+    _xdg_home[d] = ret
+    return ret
+end
+
+function xdg_cache_home()
+    if _xdg_home['CACHE'] then
+        return _xdg_home['CACHE']
+    end
+    return xdg_home('CACHE')
+end
+
+function xdg_config_home()
+    if _xdg_home['CONFIG'] then
+        return _xdg_home['CONFIG']
+    end
+    return xdg_home('CONFIG')
+end
+
+function xdg_data_home()
+    if _xdg_home['DATA'] then
+        return _xdg_home['DATA']
+    end
+    return xdg_home('DATA')
+end

freedesktop/utils.lua

@@ -1,3 +1,4 @@
+-- -*- lua-indent-level: 4; indent-tabs-mode: nil -*-
 -- Grab environment
 
 local io = io
@@ -6,6 +7,7 @@ local table = table
 local type = type
 local ipairs = ipairs
 local pairs = pairs
+local dirs = require("freedesktop.dirs")
 
 module("freedesktop.utils")
 
@@ -34,12 +36,24 @@ all_icon_types = {
     'status',
     'mimetypes'
 }
-all_icon_paths = { os.getenv("HOME") .. '/.icons/', '/usr/share/icons/' }
-
-icon_sizes = {}
+all_icon_paths = {}
 
 local mime_types = {}
 
+local function _init_all_icon_paths()
+    for _,dir in ipairs({ os.getenv("HOME") .. '/.icons/',
+                          dirs.xdg_data_home() .. 'icons/'}) do
+        if directory_exists(dir) then
+            table.insert(all_icon_paths, dir)
+        end
+    end
+    for _,dir in ipairs(dirs.xdg_data_dirs()) do
+        if directory_exists(dir .. 'icons/') then
+            table.insert(all_icon_paths, dir .. 'icons/')
+        end
+    end
+end
+
 function get_lines(...)
     local f = io.popen(...)
     return function () -- iterator
@@ -49,6 +63,17 @@ function get_lines(...)
     end
 end
 
+function directory_exists(filename)
+    local file = io.open(filename)
+    local result = (file ~= nil)
+    if result then
+        local a,b,c = file:read(0)
+        file:close()
+        result = (c == 21)
+    end
+    return result
+end
+
 function file_exists(filename)
     local file = io.open(filename, 'r')
     local result = (file ~= nil)
@@ -67,34 +92,42 @@ function lookup_icon(arg)
         local icon_themes = {}
         local icon_theme_paths = {}
         if icon_theme and type(icon_theme) == 'table' then
-            icon_themes = icon_theme
+            icon_themes = {}
+            for k,v in pairs(icon_theme) do
+                icon_themes[k] = v
+            end
         elseif icon_theme then
             icon_themes = { icon_theme }
         end
+        table.insert(icon_themes, 'hicolor')
         for i, theme in ipairs(icon_themes) do
             for j, path in ipairs(all_icon_paths) do
-                table.insert(icon_theme_paths, path .. theme .. '/')
+                if directory_exists(path .. theme) then
+                    table.insert(icon_theme_paths, path .. theme .. '/')
+                end
             end
             -- TODO also look in parent icon themes, as in freedesktop.org specification
         end
-        table.insert(icon_theme_paths, '/usr/share/icons/hicolor/') -- fallback theme cf spec
 
-        local isizes = icon_sizes
+        local isizes = {}
         for i, sz in ipairs(all_icon_sizes) do
             table.insert(isizes, sz)
         end
 
         for i, icon_theme_directory in ipairs(icon_theme_paths) do
             for j, size in ipairs(arg.icon_sizes or isizes) do
-                for k, icon_type in ipairs(all_icon_types) do
-                    table.insert(icon_path, icon_theme_directory .. size .. '/' .. icon_type .. '/')
+                if directory_exists(icon_theme_directory .. size) then
+                    for k, icon_type in ipairs(all_icon_types) do
+                        local p = icon_theme_directory .. size .. '/' .. icon_type
+                        if directory_exists(p) then
+                            table.insert(icon_path, p .. '/')
+                        end
+                    end
                 end
             end
         end
-        -- lowest priority fallbacks
+        -- lowest priority fallback
         table.insert(icon_path,  '/usr/share/pixmaps/')
-        table.insert(icon_path,  '/usr/share/icons/')
-        table.insert(icon_path,  '/usr/share/app-install/icons/')
 
         for i, directory in ipairs(icon_path) do
             if (arg.icon:find('.+%.png') or arg.icon:find('.+%.xpm')) and file_exists(directory .. arg.icon) then
@@ -253,3 +286,4 @@ function parse_dirs_and_files(arg)
     return files
 end
 
+_init_all_icon_paths()