Fix memory leak in the default config on screen removal

The default config had tables like mywibox and mywibox[s] was the wibox
that is visible on screen s. When a screen is removed, nothing cleans up
these tables and so the screen and the wibox could not be garbage
collected. The same applies to the layoutbox, taglist etc.

This commit removes the global mywibox table and instead saves it as a
property on the screen. This way, the screen is not explicitly
referenced and when it is removed, the screen, its wibox and all of its
widgets become unreachable and can be garbage collected.

This commit also updates the docs and the tests that referenced things
(mostly the wibox) via mywibox[s] to now use s.mywibox.

Fixes: https://github.com/awesomeWM/awesome/issues/1125
Signed-off-by: Uli Schlachter <psychon@znc.in>

awesomerc.lua

@@ -124,12 +124,8 @@ mykeyboardlayout = awful.widget.keyboardlayout()
 mytextclock = wibox.widget.textclock()
 
 -- Create a wibox for each screen and add it
-mywibox = {}
-mypromptbox = {}
-mylayoutbox = {}
-mytaglist = {}
 -- @TAGLIST_BUTTON@
-mytaglist.buttons = awful.util.table.join(
+local taglist_buttons = awful.util.table.join(
                     awful.button({ }, 1, function(t) t:view_only() end),
                     awful.button({ modkey }, 1, function(t)
                                               if client.focus then
@@ -146,9 +142,8 @@ mytaglist.buttons = awful.util.table.join(
                     awful.button({ }, 5, function(t) awful.tag.viewprev(t.screen) end)
                 )
 
-mytasklist = {}
 -- @TASKLIST_BUTTON@
-mytasklist.buttons = awful.util.table.join(
+local tasklist_buttons = awful.util.table.join(
                      awful.button({ }, 1, function (c)
                                               if c == client.focus then
                                                   c.minimized = true
@@ -198,42 +193,42 @@ awful.screen.connect_for_each_screen(function(s)
     awful.tag({ "1", "2", "3", "4", "5", "6", "7", "8", "9" }, s, awful.layout.layouts[1])
 
     -- Create a promptbox for each screen
-    mypromptbox[s] = awful.widget.prompt()
+    s.mypromptbox = awful.widget.prompt()
     -- Create an imagebox widget which will contains an icon indicating which layout we're using.
     -- We need one layoutbox per screen.
-    mylayoutbox[s] = awful.widget.layoutbox(s)
+    s.mylayoutbox = awful.widget.layoutbox(s)
-    mylayoutbox[s]:buttons(awful.util.table.join(
+    s.mylayoutbox:buttons(awful.util.table.join(
                            awful.button({ }, 1, function () awful.layout.inc( 1) end),
                            awful.button({ }, 3, function () awful.layout.inc(-1) end),
                            awful.button({ }, 4, function () awful.layout.inc( 1) end),
                            awful.button({ }, 5, function () awful.layout.inc(-1) end)))
     -- Create a taglist widget
-    mytaglist[s] = awful.widget.taglist(s, awful.widget.taglist.filter.all, mytaglist.buttons)
+    s.mytaglist = awful.widget.taglist(s, awful.widget.taglist.filter.all, taglist_buttons)
 
     -- Create a tasklist widget
-    mytasklist[s] = awful.widget.tasklist(s, awful.widget.tasklist.filter.currenttags, mytasklist.buttons)
+    s.mytasklist = awful.widget.tasklist(s, awful.widget.tasklist.filter.currenttags, tasklist_buttons)
 
     -- @DOC_WIBAR@
     -- Create the wibox
-    mywibox[s] = awful.wibar({ position = "top", screen = s })
+    s.mywibox = awful.wibar({ position = "top", screen = s })
 
     -- @DOC_SETUP_WIDGETS@
     -- Add widgets to the wibox
-    mywibox[s]:setup {
+    s.mywibox:setup {
         layout = wibox.layout.align.horizontal,
         { -- Left widgets
             layout = wibox.layout.fixed.horizontal,
             mylauncher,
-            mytaglist[s],
+            s.mytaglist,
-            mypromptbox[s],
+            s.mypromptbox,
         },
-        mytasklist[s], -- Middle widget
+        s.mytasklist, -- Middle widget
         { -- Right widgets
             layout = wibox.layout.fixed.horizontal,
             mykeyboardlayout,
             wibox.widget.systray(),
             mytextclock,
-            mylayoutbox[s],
+            s.mylayoutbox,
         },
     }
 end)
@@ -332,13 +327,13 @@ globalkeys = awful.util.table.join(
               {description = "restore minimized", group = "client"}),
 
     -- Prompt
-    awful.key({ modkey },            "r",     function () mypromptbox[awful.screen.focused()]:run() end,
+    awful.key({ modkey },            "r",     function () awful.screen.focused().mypromptbox:run() end,
               {description = "run prompt", group = "launcher"}),
 
     awful.key({ modkey }, "x",
               function ()
                   awful.prompt.run({ prompt = "Run Lua code: " },
-                  mypromptbox[awful.screen.focused()].widget,
+                  awful.screen.focused().mypromptbox.widget,
                   awful.util.eval, nil,
                   awful.util.get_cache_dir() .. "/history_eval")
               end,

docs/03-declarative-layout.md

@@ -39,7 +39,7 @@ and usually provide some options.
 
 Code:
 
-    mywibox[s] : setup {
+    s.mywibox : setup {
         s == 1 and my_first_widget, -- Only display on screen 1
         my_second_widget,
         { -- Add a background color/pattern for my_third_widget
@@ -66,7 +66,7 @@ declarative layout, or `nil`.
 
 Code:
 
-    mywibox[s] : setup {
+    s.mywibox : setup {
         {
             -- Force the textbox to always be 300 pixel long
             {
@@ -113,7 +113,7 @@ and `right` can be defined
 
 Code:
 
-    mywibox[s] : setup {
+    s.mywibox : setup {
         my_textbox1, -- Left
         nil,         -- Nothing in the middle
         my_textbox2, -- Right
@@ -129,7 +129,7 @@ is a simple circle widget:
 
 Code:
 
-    mywibox[s] : setup {
+    s.mywibox : setup {
         fit    = function(self, context, width, height)
             return height, height -- A square taking the full height
         end,
@@ -165,7 +165,7 @@ Code:
     tb:set_markup("Hello world! ")
     
     -- Repeat "tb" 3 times
-    mywibox[s] : setup {
+    s.mywibox : setup {
         tb,
         tb,
         tb,
@@ -198,7 +198,7 @@ underscore characters and non-numeric first character)
 
 Code:
 
-    mywibox[s] : setup {
+    s.mywibox : setup {
         {
             id     = "second",
             widget = wibox.widget.textbox
@@ -211,8 +211,8 @@ Code:
         layout = wibox.layout.fixed.horizontal,
     }
     
-    mywibox[s].first.second:set_markup("changed!")
+    s.mywibox.first.second:set_markup("changed!")
-    mywibox[s]:get_children_by_id("third")[1]:set_markup("Also changed!")
+    s.mywibox:get_children_by_id("third")[1]:set_markup("Also changed!")
 
 
 
@@ -234,7 +234,7 @@ Code:
         vicious.register(w, f(args))
     end
 
-    mywibox[s] : setup {
+    s.mywibox : setup {
         {
             vicious = {vicious.widgets.cpu, "CPU: $1%", 3},
             widget  = wibox.widget.textbox
@@ -273,7 +273,7 @@ Code:
     local l = wibox.widget.align()
     
     -- 3 circle
-    mywibox[s] : setup {
+    s.mywibox : setup {
         circle,
         circle,
         circle,
@@ -287,5 +287,5 @@ Code:
         table.insert(three_circle, circle)
     end
     
-    mywibox[s] : setup (three_circle)
+    s.mywibox : setup (three_circle)
 

docs/16-using-cairo.md

@@ -160,4 +160,4 @@ some examples. Here is the most simple example you can get:
 This can then be used as `bgimage` for a `wibox`, `awful.wibar` or
 `wibox.container.background`:
 
-    mywibox[screen.primary].bgimage = img
+    screen.primary.mywibox.bgimage = img

docs/90-FAQ.md

@@ -145,7 +145,7 @@ You can use a `clientkeys` binding.:
 Add the following key binding to your `globalkeys`:
 
     awful.key({ modkey }, "b", function ()
-        mywibox[mouse.screen].visible = not mywibox[mouse.screen].visible
+        mouse.screen.mywibox.visible = not mouse.screen.mywibox.visible
     end),
 
 ### How to toggle clients floating state?

lib/awful/prompt.lua

@@ -236,7 +236,7 @@ end
 --     hooks = {
 --       -- Apply startup notification properties with Shift-Return.
 --       {{"Shift"  }, "Return", function(command)
---         mypromptbox[awful.screen.focused()]:spawn_and_handle_error(
+--         awful.screen.focused().mypromptbox:spawn_and_handle_error(
 --           command, {floating=true})
 --       end},
 --       -- Override default behavior of "Return": launch commands prefixed

lib/awful/widget/watch.lua

@@ -20,7 +20,7 @@
 --     221                 end
 --     222               end
 --     223             end),
---     224             mylayoutbox[s],
+--     224             s.mylayoutbox,
 -- 
 -- ![Example screenshot](../images/awful_widget_watch.png)
 --

tests/test-leaks.lua

@@ -12,13 +12,12 @@ local function emit_refresh()
 end
 
 -- Make the layoutbox in the default config GC'able
--- luacheck: globals mywibox mylayoutbox
 for s in screen do
-    mywibox[s]:set_widget(wibox.widget.textbox())
+    s.mywibox:set_widget(wibox.widget.textbox())
-    mywibox[s].visible = false
+    s.mywibox.visible = false
+    s.mywibox = nil
+    s.mylayoutbox = nil
 end
-mywibox = nil
-mylayoutbox = nil
 emit_refresh()
 
 -- Test if some objects can be garbage collected

tests/test-screen-changes.lua

@@ -47,7 +47,7 @@ local steps = {
         assert(geom.width + 2*bw == 600, geom.width + 2*bw)
         assert(geom.height + 2*bw == 610, geom.height + 2*bw)
 
-        local wb = mywibox[fake_screen]
+        local wb = fake_screen.mywibox
         assert(wb.screen == fake_screen, tostring(wb.screen) .. " ~= " .. tostring(fake_screen))
         assert(wb.x == 100, wb.x)
         assert(wb.y == 110, wb.y)
@@ -58,19 +58,12 @@ local steps = {
 
     -- Step 3: Say goodbye to the screen
     function()
+        local wb = fake_screen.mywibox
         fake_screen:fake_remove()
 
         -- Now that the screen is invalid, the wibox shouldn't refer to it any
         -- more
-        assert(mywibox[fake_screen].screen ~= fake_screen)
+        assert(wb.screen ~= fake_screen)
-
-        -- TODO: This is a hack to make the test work, how to do this so that it
-        -- also works "in the wild"?
-        mypromptbox[fake_screen] = nil
-        mylayoutbox[fake_screen] = nil
-        mytaglist[fake_screen] = nil
-        mytasklist[fake_screen] = nil
-        mywibox[fake_screen] = nil
 
         -- Wrap in a weak table to allow garbage collection
         fake_screen = setmetatable({ fake_screen }, { __mode = "v" })

tests/test-struts.lua

@@ -2,12 +2,11 @@ local placement   = require("awful.placement")
 local wibox       = require("wibox")
 local wibar       = require("awful.wibar")
 
--- luacheck: globals mywibox
 local steps = {}
 
 local parent, small
 
-local twibar, bwibar, lwibar, rwibar = mywibox[screen.primary]
+local twibar, bwibar, lwibar, rwibar = screen.primary.mywibox
 
 -- Test the struts without using wibars
 table.insert(steps, function()