Fix luacheck warnings in tests/_multi_screen.lua

This is a partial revert of commit 7901a1c647. The end result is the
same, but the change from that commit is reverted and instead the same
thing is done in a different way.

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

tests/_multi_screen.lua

@@ -1,3 +1,6 @@
+-- FIXME See commit 7901a1c6479aea
+local skip_wallpapers_due_to_weird_slowdowns = true
+
 -- Helper module to replicate a set of steps across multiple screen scenarios
 -- Ideas for improvements:
 --  * Export an iterator so the suits can call the screen change step by step
@@ -348,58 +351,60 @@ local colors = {
 
 -- Paint it black
 local function clear_screen()
---     for s in screen do --FIXME very, very slow on Travis
---         local sur = surface.widget_to_surface(
---             wibox.widget {
---                 bg     = "#000000",
---                 widget = wibox.container.background
---             },
---             s.geometry.width,
---             s.geometry.height
---         )
---         wallpaper.fit(sur, s, "#000000")
---     end
+    if skip_wallpapers_due_to_weird_slowdowns then
+        return
+    end
+    for s in screen do
+         local sur = surface.widget_to_surface(
+             wibox.widget {
+                 bg     = "#000000",
+                 widget = wibox.container.background
+             },
+             s.geometry.width,
+             s.geometry.height
+         )
+         wallpaper.fit(sur, s, "#000000")
+     end
 end
 
 -- Make it easier to debug the tests by showing the screen geometry when the
 -- tests are executed.
 local function show_screens()
-    --FIXME very, very slow on Travis
---     wallpaper.set(color("#000000")) -- Should this clear the wallpaper? It doesn't
--- 
---     -- Add a wallpaper on each screen
---     for i=1, screen.count() do
---         local s = screen[i]
--- 
---         local w = wibox.widget {
---             {
---                 text   = table.concat{
---                     "Screen: ",i,"\n",
---                     s.geometry.width,"x",s.geometry.height,
---                     "+",s.geometry.x,",",s.geometry.y
---                 },
---                 valign = "center",
---                 align  = "center",
---                 widget = wibox.widget.textbox,
---             },
---             bg                 = colors[i],
---             fg                 = "#ffffff",
---             shape_border_color = "#ff0000",
---             shape_border_width = 1,
---             shape              = shape.rectangle,
---             widget             = wibox.container.background
---         }
---         local sur = surface.widget_to_surface(
---             w,
---             s.geometry.width,
---             s.geometry.height
---         )
---         wallpaper.fit(sur, s)
---     end
+    if skip_wallpapers_due_to_weird_slowdowns then
+        wallpaper.maximized = function() end
+        return
+    end
+    wallpaper.set(color("#000000")) -- Should this clear the wallpaper? It doesn't
 
-    --TODO remove this line, all it does it saving some time in the tests until
-    -- the bug is fixed.
-    wallpaper.maximized = function() end
+    -- Add a wallpaper on each screen
+    for i=1, screen.count() do
+        local s = screen[i]
+
+        local w = wibox.widget {
+            {
+                text   = table.concat{
+                    "Screen: ",i,"\n",
+                    s.geometry.width,"x",s.geometry.height,
+                    "+",s.geometry.x,",",s.geometry.y
+                },
+                valign = "center",
+                align  = "center",
+                widget = wibox.widget.textbox,
+            },
+            bg                 = colors[i],
+            fg                 = "#ffffff",
+            shape_border_color = "#ff0000",
+            shape_border_width = 1,
+            shape              = shape.rectangle,
+            widget             = wibox.container.background
+        }
+        local sur = surface.widget_to_surface(
+            w,
+            s.geometry.width,
+            s.geometry.height
+        )
+        wallpaper.fit(sur, s)
+    end
 end
 
 local function add_steps(real_steps, new_steps)