only operate on surface copies

Working with icons is tricky because their surfaces do not use reference counting correctly. If gears.surface(c.icon) is called multiple time on the same icon, it will cause a double-free error and Awesome will crash.

init.lua

@@ -1,16 +1,20 @@
 local gears = require("gears")
 local awful = require("awful")
 local theme = require("beautiful")
+local cairo = require("lgi").cairo
 
 local module = {}
 
+-- luacheck: globals client
 local client = client
 
 local icons, dynamic_icons, dynamic_classes, delay
 
 local function len(T)
     local count = 0
-	for _ in pairs(T) do count = count + 1 end
+    for _ in pairs(T) do
+        count = count + 1
+    end
     return count
 end
 
@@ -23,14 +27,26 @@ local function contains(T, V)
     return false
 end
 
+local function icon_copy(icon)
+    if not icon then
+        return nil
+    end
+    local s = gears.surface(icon)
+    local img = cairo.ImageSurface.create(cairo.Format.ARGB32, s:get_width(), s:get_height())
+    local cr = cairo.Context(img)
+    cr:set_source_surface(s, 0, 0)
+    cr:paint()
+    return img
+end
+
 local function set_icon(c, icon)
     if c and c.valid then
         if not c.icon_backup then
-			c.icon_backup = icons[c.class] and gears.surface(icons[c.class]) or gears.surface(c.icon)
+            c.icon_backup = icon_copy(icons[c.class]) or icon_copy(c.icon)
         end
+        icon = icon_copy(icon)
         if icon then
-			icon = gears.surface(icon)
-			c.icon = icon and icon._native or nil
+            c.icon = icon._native
         end
     end
 end
@@ -46,7 +62,7 @@ local function set_dynamic_icon(c)
     end
 
     if c.icon_backup then
-		c.icon = c.icon_backup and c.icon_backup._native or nil
+        c.icon = c.icon_backup._native or nil
     end
 end
 
@@ -58,10 +74,18 @@ local function setup(config)
     dynamic_classes = cfg.dynamic_classes or theme.ic_dynamic_classes or {}
     delay = cfg.delay or 0.5
 
-	if type(icons) ~= 'table' then icons = {} end
-	if type(dynamic_icons) ~= 'table' then dynamic_icons = {} end
-	if type(dynamic_classes) ~= 'table' then dynamic_classes = {} end
-	if type(delay) ~= 'number' then delay = 0.5 end
+    if type(icons) ~= 'table' then
+        icons = {}
+    end
+    if type(dynamic_icons) ~= 'table' then
+        dynamic_icons = {}
+    end
+    if type(dynamic_classes) ~= 'table' then
+        dynamic_classes = {}
+    end
+    if type(delay) ~= 'number' then
+        delay = 0.5
+    end
 
     client.connect_signal("manage", function(c)
         -- set icon based on c.class
@@ -89,7 +113,8 @@ local function setup(config)
     end)
 end
 
-return setmetatable(module, { __call = function(_, ...)
+return setmetatable(module, {
+    __call = function(_, ...)
         setup(...)
         -- we have to update all clients icons manually when the user restarts awesomewm
         -- since there is no "property::name" signal emitted by already running clients.
@@ -101,4 +126,5 @@ return setmetatable(module, { __call = function(_, ...)
                 end
             end
         end)
-end })
+    end
+})