diff --git a/lib/gears/cache.lua b/lib/gears/cache.lua
index 7329a1e7..905f58b0 100644
--- a/lib/gears/cache.lua
+++ b/lib/gears/cache.lua
@@ -7,7 +7,7 @@
 
 local select = select
 local setmetatable = setmetatable
-local unpack = unpack or table.unpack
+local unpack = unpack or table.unpack -- luacheck: globals unpack (compatibility with Lua 5.1)
 
 local cache = {}
 
diff --git a/lib/gears/color.lua b/lib/gears/color.lua
index 63533c48..5454dfc3 100644
--- a/lib/gears/color.lua
+++ b/lib/gears/color.lua
@@ -8,7 +8,7 @@
 local setmetatable = setmetatable
 local string = string
 local table = table
-local unpack = unpack or table.unpack -- v5.1: unpack, v5.2: table.unpack
+local unpack = unpack or table.unpack -- luacheck: globals unpack (compatibility with Lua 5.1)
 local tonumber = tonumber
 local ipairs = ipairs
 local pairs = pairs
@@ -88,7 +88,6 @@ end
 -- @param col The color for the pattern
 -- @return A cairo pattern object
 function color.create_solid_pattern(col)
-    local col = col
     if col == nil then
         col = "#000000"
     elseif type(col) == "table" then
@@ -102,7 +101,6 @@ end
 -- @param file The filename of the file
 -- @return a cairo pattern object
 function color.create_png_pattern(file)
-    local file = file
     if type(file) == "table" then
         file = file.file
     end
@@ -138,7 +136,7 @@ local function string_pattern(creator, arg)
     local args = { parse_numbers(iterator()) }
     local to = { parse_numbers(iterator()) }
     -- Now merge those two tables
-    for k, v in pairs(to) do
+    for _, v in pairs(to) do
         table.insert(args, v)
     end
     -- And call our creator function with the values
@@ -220,7 +218,7 @@ function color.create_pattern_uncached(col)
     if cairo.Pattern:is_type_of(col) then
         return col
     end
-    local col = col or "#000000"
+    col = col or "#000000"
     if type(col) == "string" then
         local t = string.match(col, "[^:]+")
         if color.types[t] then
@@ -271,18 +269,17 @@ end
 -- @return The pattern if it is surely opaque, else nil
 function color.create_opaque_pattern(col)
     local pattern = color.create_pattern(col)
-    local type = pattern:get_type()
-    local extend = pattern:get_extend()
+    local kind = pattern:get_type()
 
-    if type == "SOLID" then
-        local status, r, g, b, a = pattern:get_rgba()
-        if a ~= 1 then
+    if kind == "SOLID" then
+        local _, _, _, _, alpha = pattern:get_rgba()
+        if alpha ~= 1 then
             return
         end
         return pattern
-    elseif type == "SURFACE" then
-        local status, surface = pattern:get_surface()
-        if status ~= "SUCCESS" or surface.content ~= "COLOR" then
+    elseif kind == "SURFACE" then
+        local status, surf = pattern:get_surface()
+        if status ~= "SUCCESS" or surf.content ~= "COLOR" then
             -- The surface has an alpha channel which *might* be non-opaque
             return
         end
@@ -294,8 +291,8 @@ function color.create_opaque_pattern(col)
         end
 
         return pattern
-    elseif type == "LINEAR" then
-        local status, stops = pattern:get_color_stop_count()
+    elseif kind == "LINEAR" then
+        local _, stops = pattern:get_color_stop_count()
 
         -- No color stops or extend NONE -> pattern *might* contain transparency
         if stops == 0 or pattern:get_extend() == "NONE" then
@@ -304,8 +301,8 @@ function color.create_opaque_pattern(col)
 
         -- Now check if any of the color stops contain transparency
         for i = 0, stops - 1 do
-            local status, offset, r, g, b, a = pattern:get_color_stop_rgba(i)
-            if a ~= 1 then
+            local _, _, _, _, _, alpha = pattern:get_color_stop_rgba(i)
+            if alpha ~= 1 then
                 return
             end
         end
@@ -330,7 +327,7 @@ function color.recolor_image(image, new_color)
     return image
 end
 
-function color.mt:__call(...)
+function color.mt.__call(_, ...)
     return color.create_pattern(...)
 end
 
diff --git a/lib/gears/debug.lua b/lib/gears/debug.lua
index af323e2e..ec27ed5d 100644
--- a/lib/gears/debug.lua
+++ b/lib/gears/debug.lua
@@ -5,9 +5,7 @@
 -- @module gears.debug
 ---------------------------------------------------------------------------
 
-local error = error
 local tostring = tostring
-local traceback = debug.traceback
 local print = print
 local type = type
 local pairs = pairs
diff --git a/lib/gears/matrix.lua b/lib/gears/matrix.lua
index 687a4f96..ed91915e 100644
--- a/lib/gears/matrix.lua
+++ b/lib/gears/matrix.lua
@@ -175,7 +175,7 @@ end
 -- @treturn number The x coordinate of the transformed point.
 -- @treturn number The x coordinate of the transformed point.
 function matrix:transform_point(x, y)
-    local x, y = self:transform_distance(x, y)
+    x, y = self:transform_distance(x, y)
     return self.x0 + x, self.y0 + y
 end
 
@@ -195,10 +195,10 @@ function matrix:transform_rectangle(x, y, width, height)
     local x3, y3 = self:transform_point(x + width, y + height)
     local x4, y4 = self:transform_point(x + width, y)
     -- Find the extremal points of the result
-    local x = math.min(x1, x2, x3, x4)
-    local y = math.min(y1, y2, y3, y4)
-    local width = math.max(x1, x2, x3, x4) - x
-    local height = math.max(y1, y2, y3, y4) - y
+    x = math.min(x1, x2, x3, x4)
+    y = math.min(y1, y2, y3, y4)
+    width = math.max(x1, x2, x3, x4) - x
+    height = math.max(y1, y2, y3, y4) - y
 
     return x, y, width, height
 end
diff --git a/lib/gears/object.lua b/lib/gears/object.lua
index e2f9ef02..2eb230cd 100644
--- a/lib/gears/object.lua
+++ b/lib/gears/object.lua
@@ -60,6 +60,7 @@ local function make_the_gc_obey(func)
         -- Lua 5.1 only has the behaviour we want if a userdata is used as the
         -- value in a weak table. Thus, do some magic so that we get a userdata.
 
+        -- luacheck: globals newproxy getfenv setfenv
         local userdata = newproxy(true)
         getmetatable(userdata).__gc = function() end
         -- Now bind the lifetime of userdata to the lifetime of func. For this,
@@ -137,7 +138,7 @@ local function new()
     return ret
 end
 
-function object.mt:__call(...)
+function object.mt.__call(_, ...)
     return new(...)
 end
 
diff --git a/lib/gears/shape.lua b/lib/gears/shape.lua
index 76b16f87..eff81489 100644
--- a/lib/gears/shape.lua
+++ b/lib/gears/shape.lua
@@ -64,9 +64,9 @@ end
 -- @tparam[opt=10] number arrow_size The width and height of the arrow
 -- @tparam[opt=width/2 - arrow_size/2] number arrow_position The position of the arrow
 function module.infobubble(cr, width, height, corner_radius, arrow_size, arrow_position)
-    local corner_radius  = corner_radius  or 5
-    local arrow_size     = arrow_size     or 10
-    local arrow_position = arrow_position or width/2 - arrow_size/2
+    corner_radius  = corner_radius  or 5
+    arrow_size     = arrow_size     or 10
+    arrow_position = arrow_position or width/2 - arrow_size/2
 
     cr:move_to(0 ,corner_radius)
 
@@ -109,9 +109,9 @@ end
 -- @tparam[opt=width /2] number shaft_width The width of the shaft of the arrow
 -- @tparam[opt=height/2] number shaft_length The head_length of the shaft (the rest is the head)
 function module.arrow(cr, width, height, head_width, shaft_width, shaft_length)
-    local shaft_length = shaft_length or height / 2
-    local shaft_width  = shaft_width  or width  / 2
-    local head_width   = head_width   or width
+    shaft_length = shaft_length or height / 2
+    shaft_width  = shaft_width  or width  / 2
+    head_width   = head_width   or width
     local head_length  = height - shaft_length
 
     cr:move_to    ( width/2                     , 0            )
@@ -146,7 +146,7 @@ end
 -- @tparam number height The shape height
 -- @tparam[opt=height/2] number arrow_depth The width of the arrow part of the shape
 function module.powerline(cr, width, height, arrow_depth)
-    local arrow_depth = arrow_depth or height/2
+    arrow_depth = arrow_depth or height/2
     cr:move_to(0                   , 0        )
     cr:line_to(width - arrow_depth , 0        )
     cr:line_to(width               , height/2 )
diff --git a/lib/gears/surface.lua b/lib/gears/surface.lua
index 64afabea..ed9e7b9c 100644
--- a/lib/gears/surface.lua
+++ b/lib/gears/surface.lua
@@ -114,7 +114,7 @@ function surface.load(_surface)
     return do_load_and_handle_errors(_surface, surface.load_silently)
 end
 
-function surface.mt:__call(...)
+function surface.mt.__call(_, ...)
     return surface.load(...)
 end
 
diff --git a/lib/gears/timer.lua b/lib/gears/timer.lua
index 6eee64be..1c50cefe 100644
--- a/lib/gears/timer.lua
+++ b/lib/gears/timer.lua
@@ -14,7 +14,7 @@ local setmetatable = setmetatable
 local table = table
 local tonumber = tonumber
 local traceback = debug.traceback
-local unpack = unpack or table.unpack -- v5.1: unpack, v5.2: table.unpack
+local unpack = unpack or table.unpack -- luacheck: globals unpack (compatibility with Lua 5.1)
 local glib = require("lgi").GLib
 local object = require("gears.object")
 
@@ -43,7 +43,7 @@ function timer:start()
         return
     end
     self.data.source_id = glib.timeout_add(glib.PRIORITY_DEFAULT, self.data.timeout * 1000, function()
-        local success, message = xpcall(function()
+        xpcall(function()
                 self:emit_signal("timeout")
             end, function(err)
                 print(debug.traceback("Error during executing timeout handler: "..tostring(err)))
@@ -160,7 +160,7 @@ end
 local delayed_calls = {}
 capi.awesome.connect_signal("refresh", function()
     for _, callback in ipairs(delayed_calls) do
-        local success, message = xpcall(function()
+        xpcall(function()
                 callback[1](unpack(callback, 2))
             end, function(err)
                 print(debug.traceback("Error during delayed call: "..tostring(err), 2))
@@ -177,7 +177,7 @@ function timer.delayed_call(callback, ...)
     table.insert(delayed_calls, { callback, ... })
 end
 
-function timer.mt:__call(...)
+function timer.mt.__call(_, ...)
     return timer.new(...)
 end
 
diff --git a/lib/gears/wallpaper.lua b/lib/gears/wallpaper.lua
index e09262a9..aba2464e 100644
--- a/lib/gears/wallpaper.lua
+++ b/lib/gears/wallpaper.lua
@@ -58,9 +58,9 @@ function wallpaper.prepare_context(s)
 
         -- Set the wallpaper (delayed)
         timer.delayed_call(function()
-            local wp = pending_wallpaper
+            local paper = pending_wallpaper
             pending_wallpaper = nil
-            wallpaper.set(wp)
+            wallpaper.set(paper)
         end)
     else
         -- Draw to the already-pending wallpaper
@@ -99,8 +99,8 @@ end
 --   gears.color. The default is black.
 function wallpaper.centered(surf, s, background)
     local geom, cr = wallpaper.prepare_context(s)
-    local surf = surface(surf)
-    local background = color(background)
+    surf = surface(surf)
+    background = color(background)
 
     -- Fill the area with the background
     cr.operator = cairo.Operator.SOURCE
@@ -122,7 +122,7 @@ end
 --   all screens are set.
 -- @param offset This can be set to a table with entries x and y.
 function wallpaper.tiled(surf, s, offset)
-    local geom, cr = wallpaper.prepare_context(s)
+    local _, cr = wallpaper.prepare_context(s)
 
     if offset then
         cr:translate(offset.x, offset.y)
@@ -144,7 +144,7 @@ end
 -- @param offset This can be set to a table with entries x and y.
 function wallpaper.maximized(surf, s, ignore_aspect, offset)
     local geom, cr = wallpaper.prepare_context(s)
-    local surf = surface(surf)
+    surf = surface(surf)
     local w, h = surface.get_size(surf)
     local aspect_w = geom.width / w
     local aspect_h = geom.height / h
@@ -176,8 +176,8 @@ end
 --   gears.color. The default is black.
 function wallpaper.fit(surf, s, background)
     local geom, cr = wallpaper.prepare_context(s)
-    local surf = surface(surf)
-    local background = color(background)
+    surf = surface(surf)
+    background = color(background)
 
     -- Fill the area with the background
     cr.operator = cairo.Operator.SOURCE
diff --git a/lib/naughty/core.lua b/lib/naughty/core.lua
index b8bdf8f7..817b81ae 100644
--- a/lib/naughty/core.lua
+++ b/lib/naughty/core.lua
@@ -12,7 +12,6 @@ local pairs = pairs
 local table = table
 local type = type
 local string = string
-local tostring = tostring
 local pcall = pcall
 local capi = { screen = screen,
                awesome = awesome }
@@ -26,11 +25,6 @@ local surface = require("gears.surface")
 local cairo = require("lgi").cairo
 local dpi = require("beautiful").xresources.apply_dpi
 
-local schar = string.char
-local sbyte = string.byte
-local tcat = table.concat
-local tins = table.insert
-
 local naughty = {}
 
 --[[--
@@ -169,7 +163,7 @@ end
 --- Resume notifications
 function naughty.resume()
     suspended = false
-    for i, v in pairs(naughty.notifications.suspended) do
+    for _, v in pairs(naughty.notifications.suspended) do
         v.box.visible = true
         if v.timer then v.timer:start() end
     end
@@ -187,18 +181,18 @@ end
 
 --- Evaluate desired position of the notification by index - internal
 --
--- @param screen Screen to use
+-- @param s Screen to use
 -- @param position top_right | top_left | bottom_right | bottom_left
 --   | top_middle | bottom_middle
 -- @param idx Index of the notification
 -- @param[opt] width Popup width.
 -- @param height Popup height
 -- @return Absolute position and index in { x = X, y = Y, idx = I } table
-local function get_offset(screen, position, idx, width, height)
-    local ws = capi.screen[screen].workarea
+local function get_offset(s, position, idx, width, height)
+    local ws = capi.screen[s].workarea
     local v = {}
-    local idx = idx or #naughty.notifications[screen][position] + 1
-    local width = width or naughty.notifications[screen][position][idx].width
+    idx = idx or #naughty.notifications[s][position] + 1
+    width = width or naughty.notifications[s][position][idx].width
 
     -- calculate x
     if position:match("left") then
@@ -212,7 +206,7 @@ local function get_offset(screen, position, idx, width, height)
     -- calculate existing popups' height
     local existing = 0
     for i = 1, idx-1, 1 do
-        existing = existing + naughty.notifications[screen][position][i].height + naughty.config.spacing
+        existing = existing + naughty.notifications[s][position][i].height + naughty.config.spacing
     end
 
     -- calculate y
@@ -227,20 +221,20 @@ local function get_offset(screen, position, idx, width, height)
     -- e.g. critical ones.
     local find_old_to_replace = function()
         for i = 1, idx-1 do
-            local n = naughty.notifications[screen][position][i]
+            local n = naughty.notifications[s][position][i]
             if n.timeout > 0 then
                 return n
             end
         end
         -- Fallback to first one.
-        return naughty.notifications[screen][position][1]
+        return naughty.notifications[s][position][1]
     end
 
     -- if positioned outside workarea, destroy oldest popup and recalculate
     if v.y + height > ws.y + ws.height or v.y < ws.y then
         naughty.destroy(find_old_to_replace())
         idx = idx - 1
-        v = get_offset(screen, position, idx, width, height)
+        v = get_offset(s, position, idx, width, height)
     end
     if not v.idx then v.idx = idx end
 
@@ -250,10 +244,10 @@ end
 --- Re-arrange notifications according to their position and index - internal
 --
 -- @return None
-local function arrange(screen)
-    for p,pos in pairs(naughty.notifications[screen]) do
-        for i,notification in pairs(naughty.notifications[screen][p]) do
-            local offset = get_offset(screen, p, i, notification.width, notification.height)
+local function arrange(s)
+    for p in pairs(naughty.notifications[s]) do
+        for i,notification in pairs(naughty.notifications[s][p]) do
+            local offset = get_offset(s, p, i, notification.width, notification.height)
             notification.box:geometry({ x = offset.x, y = offset.y })
             notification.idx = offset.idx
         end
@@ -296,8 +290,8 @@ end
 function naughty.getById(id)
     -- iterate the notifications to get the notfications with the correct ID
     for s = 1, capi.screen.count() do
-        for p,pos in pairs(naughty.notifications[s]) do
-            for i,notification in pairs(naughty.notifications[s][p]) do
+        for p in pairs(naughty.notifications[s]) do
+            for _, notification in pairs(naughty.notifications[s][p]) do
                 if notification.id == id then
                     return notification
                  end
@@ -437,7 +431,7 @@ function naughty.notify(args)
     local icon_size = args.icon_size or preset.icon_size
     local text = args.text or preset.text
     local title = args.title or preset.title
-    local screen = args.screen or preset.screen or screen.focused()
+    local s = args.screen or preset.screen or screen.focused()
     local ontop = args.ontop or preset.ontop
     local width = args.width or preset.width
     local height = args.height or preset.height
@@ -455,7 +449,7 @@ function naughty.notify(args)
     local fg = args.fg or preset.fg or beautiful.fg_normal or '#ffffff'
     local bg = args.bg or preset.bg or beautiful.bg_normal or '#535d6c'
     local border_color = args.border_color or preset.border_color or beautiful.bg_focus or '#535d6c'
-    local notification = { screen = screen, destroy_cb = destroy_cb, timeout = timeout }
+    local notification = { screen = s, destroy_cb = destroy_cb, timeout = timeout }
 
     -- replace notification if needed
     if args.replaces_id then
@@ -530,8 +524,8 @@ function naughty.notify(args)
             actiontextbox:set_markup(string.format('<b>%s</b>', action))
             -- calculate the height and width
             local w, h = actiontextbox:get_preferred_size(s)
-            local height = h + 2 * margin
-            local width = w + 2 * margin
+            local action_height = h + 2 * margin
+            local action_width = w + 2 * margin
 
             actionmarginbox:buttons(util.table.join(
                 button({ }, 1, callback),
@@ -539,9 +533,9 @@ function naughty.notify(args)
                 ))
             actionslayout:add(actionmarginbox)
 
-            actions_total_height = actions_total_height + height
-            if actions_max_width < width then
-                actions_max_width = width
+            actions_total_height = actions_total_height + action_height
+            if actions_max_width < action_width then
+                actions_max_width = action_width
             end
         end
     end
@@ -561,7 +555,7 @@ function naughty.notify(args)
         end
 
         -- is the icon file readable?
-        local icon = surface.load_uncached(icon)
+        icon = surface.load_uncached(icon)
 
         -- if we have an icon, use it
         if icon then
@@ -593,7 +587,7 @@ function naughty.notify(args)
 
     -- calculate the width
     if not width then
-        local w, h = textbox:get_preferred_size(s)
+        local w, _ = textbox:get_preferred_size(s)
         width = w + (iconbox and icon_w + 2 * margin or 0) + 2 * margin
     end
 
@@ -615,7 +609,7 @@ function naughty.notify(args)
     height = height + actions_total_height
 
     -- crop to workarea size if too big
-    local workarea = capi.screen[screen].workarea
+    local workarea = capi.screen[s].workarea
     if width > workarea.width - 2 * (border_width or 0) - 2 * (naughty.config.padding or 0) then
         width = workarea.width - 2 * (border_width or 0) - 2 * (naughty.config.padding or 0)
     end
@@ -628,7 +622,7 @@ function naughty.notify(args)
     notification.width = width + 2 * (border_width or 0)
 
     -- position the wibox
-    local offset = get_offset(screen, notification.position, nil, notification.width, notification.height)
+    local offset = get_offset(s, notification.position, nil, notification.width, notification.height)
     notification.box.ontop = ontop
     notification.box:geometry({ width = width,
                                 height = height,
@@ -657,7 +651,7 @@ function naughty.notify(args)
                                     end)))
 
     -- insert the notification to the table
-    table.insert(naughty.notifications[screen][notification.position], notification)
+    table.insert(naughty.notifications[s][notification.position], notification)
 
     if suspended then
         notification.box.visible = false
diff --git a/lib/naughty/dbus.lua b/lib/naughty/dbus.lua
index 9673393a..9f749f9d 100644
--- a/lib/naughty/dbus.lua
+++ b/lib/naughty/dbus.lua
@@ -23,7 +23,7 @@ local schar = string.char
 local sbyte = string.byte
 local tcat = table.concat
 local tins = table.insert
-local unpack = unpack or table.unpack -- v5.1: unpack, v5.2: table.unpack
+local unpack = unpack or table.unpack -- luacheck: globals unpack (compatibility with Lua 5.1)
 local naughty = require("naughty.core")
 
 --- Notification library, dbus bindings
@@ -88,7 +88,7 @@ local function convert_icon(w, h, rowstride, channels, data)
     -- Now convert each row on its own
     local rows = {}
 
-    for y = 1, h do
+    for _ = 1, h do
         local this_row = {}
 
         for i = 1 + offset, w * channels + offset, channels do
@@ -124,8 +124,8 @@ capi.dbus.connect_signal("org.freedesktop.Notifications", function (data, appnam
         if appname ~= "" then
             args.appname = appname
         end
-        for i, obj in pairs(dbus.config.mapping) do
-            local filter, preset, s = obj[1], obj[2], 0
+        for _, obj in pairs(dbus.config.mapping) do
+            local filter, preset = obj[1], obj[2]
             if (not filter.urgency or filter.urgency == hints.urgency) and
                (not filter.category or filter.category == hints.category) and
                (not filter.appname or filter.appname == appname) then
@@ -176,8 +176,8 @@ capi.dbus.connect_signal("org.freedesktop.Notifications", function (data, appnam
                 -- 5 -> bits per sample
                 -- 6 -> channels
                 -- 7 -> data
-                local w, h, rowstride, _, _, channels, data = unpack(hints.icon_data)
-                args.icon = convert_icon(w, h, rowstride, channels, data)
+                local w, h, rowstride, _, _, channels, icon_data = unpack(hints.icon_data)
+                args.icon = convert_icon(w, h, rowstride, channels, icon_data)
             end
             if replaces_id and replaces_id ~= "" and replaces_id ~= 0 then
                 args.replaces_id = replaces_id
@@ -204,7 +204,7 @@ capi.dbus.connect_signal("org.freedesktop.Notifications", function (data, appnam
     end
 end)
 
-capi.dbus.connect_signal("org.freedesktop.DBus.Introspectable", function (data, text)
+capi.dbus.connect_signal("org.freedesktop.DBus.Introspectable", function (data)
     if data.member == "Introspect" then
         local xml = [=[<!DOCTYPE node PUBLIC "-//freedesktop//DTD D-BUS Object
     Introspection 1.0//EN"
diff --git a/lib/wibox/drawable.lua b/lib/wibox/drawable.lua
index b3b6e2dc..59bce59f 100644
--- a/lib/wibox/drawable.lua
+++ b/lib/wibox/drawable.lua
@@ -20,8 +20,7 @@ local surface = require("gears.surface")
 local timer = require("gears.timer")
 local matrix = require("gears.matrix")
 local hierarchy = require("wibox.hierarchy")
-local base = require("wibox.widget.base")
-local unpack = unpack or table.unpack
+local unpack = unpack or table.unpack -- luacheck: globals unpack (compatibility with Lua 5.1)
 
 local drawables = setmetatable({}, { __mode = 'k' })
 local wallpaper = nil
@@ -154,32 +153,32 @@ local function do_redraw(self)
     assert(cr.status == "SUCCESS", "Cairo context entered error state: " .. cr.status)
 end
 
-local function find_widgets(drawable, result, hierarchy, x, y)
-    local m = hierarchy:get_matrix_from_device()
+local function find_widgets(_drawable, result, _hierarchy, x, y)
+    local m = _hierarchy:get_matrix_from_device()
 
     -- Is (x,y) inside of this hierarchy or any child (aka the draw extents)
     local x1, y1 = m:transform_point(x, y)
-    local x2, y2, width, height = hierarchy:get_draw_extents()
-    if x1 < x2 or x1 >= x2 + width then
+    local x2, y2, w2, h2 = _hierarchy:get_draw_extents()
+    if x1 < x2 or x1 >= x2 + w2 then
         return
     end
-    if y1 < y2 or y1 >= y2 + height then
+    if y1 < y2 or y1 >= y2 + h2 then
         return
     end
 
     -- Is (x,y) inside of this widget?
-    local width, height = hierarchy:get_size()
+    local width, height = _hierarchy:get_size()
     if x1 >= 0 and y1 >= 0 and x1 <= width and y1 <= height then
         -- Get the extents of this widget in the device space
-        local x2, y2, w2, h2 = matrix.transform_rectangle(hierarchy:get_matrix_to_device(),
+        local x3, y3, w3, h3 = matrix.transform_rectangle(_hierarchy:get_matrix_to_device(),
             0, 0, width, height)
         table.insert(result, {
-            x = x2, y = y2, width = w2, height = h2,
-            drawable = drawable, widget = hierarchy:get_widget()
+            x = x3, y = y3, width = w3, height = h3,
+            drawable = _drawable, widget = _hierarchy:get_widget()
         })
     end
-    for _, child in ipairs(hierarchy:get_children()) do
-        find_widgets(drawable, result, child, x, y)
+    for _, child in ipairs(_hierarchy:get_children()) do
+        find_widgets(_drawable, result, child, x, y)
     end
 end
 
@@ -211,7 +210,7 @@ end
 -- @param c The background to use. This must either be a cairo pattern object,
 --   nil or a string that gears.color() understands.
 function drawable:set_bg(c)
-    local c = c or "#000000"
+    c = c or "#000000"
     local t = type(c)
 
     if t == "string" or t == "table" then
@@ -255,7 +254,7 @@ end
 -- @param c The foreground to use. This must either be a cairo pattern object,
 --   nil or a string that gears.color() understands.
 function drawable:set_fg(c)
-    local c = c or "#FFFFFF"
+    c = c or "#FFFFFF"
     if type(c) == "string" or type(c) == "table" then
         c = color(c)
     end
@@ -265,7 +264,7 @@ end
 
 local function emit_difference(name, list, skip)
     local function in_table(table, val)
-        for k, v in pairs(table) do
+        for _, v in pairs(table) do
             if v.widget == val.widget then
                 return true
             end
@@ -273,7 +272,7 @@ local function emit_difference(name, list, skip)
         return false
     end
 
-    for k, v in pairs(list) do
+    for _, v in pairs(list) do
         if not in_table(skip, v) then
             v.widget:emit_signal(name,v)
         end
@@ -371,9 +370,9 @@ function drawable.new(d, widget_context_skeleton, drawable_name)
     ret._widgets_under_mouse = {}
 
     local function button_signal(name)
-        d:connect_signal(name, function(d, x, y, button, modifiers)
+        d:connect_signal(name, function(_, x, y, button, modifiers)
             local widgets = ret:find_widgets(x, y)
-            for k, v in pairs(widgets) do
+            for _, v in pairs(widgets) do
                 -- Calculate x/y inside of the widget
                 local lx = x - v.x
                 local ly = y - v.y
@@ -388,12 +387,12 @@ function drawable.new(d, widget_context_skeleton, drawable_name)
     d:connect_signal("mouse::leave", function() handle_leave(ret) end)
 
     -- Set up our callbacks for repaints
-    ret._redraw_callback = function(hierarchy, arg)
+    ret._redraw_callback = function(hierar, arg)
         if ret._widget_hierarchy_callback_arg ~= arg then
             return
         end
-        local m = hierarchy:get_matrix_to_device()
-        local x, y, width, height = matrix.transform_rectangle(m, hierarchy:get_draw_extents())
+        local m = hierar:get_matrix_to_device()
+        local x, y, width, height = matrix.transform_rectangle(m, hierar:get_draw_extents())
         local x1, y1 = math.floor(x), math.floor(y)
         local x2, y2 = math.ceil(x + width), math.ceil(y + height)
         ret._dirty_area:union_rectangle(cairo.RectangleInt{
@@ -401,7 +400,7 @@ function drawable.new(d, widget_context_skeleton, drawable_name)
         })
         ret:draw()
     end
-    ret._layout_callback = function(hierarchy, arg)
+    ret._layout_callback = function(_, arg)
         if ret._widget_hierarchy_callback_arg ~= arg then
             return
         end
@@ -413,7 +412,7 @@ function drawable.new(d, widget_context_skeleton, drawable_name)
     ret.drawable_name = drawable_name or object.modulename(3)
     local mt = {}
     local orig_string = tostring(ret)
-    mt.__tostring = function(o)
+    mt.__tostring = function()
         return string.format("%s (%s)", ret.drawable_name, orig_string)
     end
     ret = setmetatable(ret, mt)
@@ -426,7 +425,6 @@ end
 
 -- Redraw all drawables when the wallpaper changes
 capi.awesome.connect_signal("wallpaper_changed", function()
-    local k
     wallpaper = nil
     for k in pairs(drawables) do
         k()
diff --git a/lib/wibox/hierarchy.lua b/lib/wibox/hierarchy.lua
index feaf9827..502d912f 100644
--- a/lib/wibox/hierarchy.lua
+++ b/lib/wibox/hierarchy.lua
@@ -16,7 +16,7 @@ local no_parent = base.no_parent_I_know_what_I_am_doing
 
 local hierarchy = {}
 
-local function hierarchy_new(widget, redraw_callback, layout_callback, callback_arg)
+local function hierarchy_new(redraw_callback, layout_callback, callback_arg)
     local result = {
         _matrix = matrix.identity,
         _matrix_to_device = matrix.identity,
@@ -107,7 +107,7 @@ function hierarchy_update(self, context, widget, width, height, region, matrix_t
     for _, w in ipairs(layout_result or {}) do
         local r = table.remove(old_children, 1)
         if not r then
-            r = hierarchy_new(w._widget, self._redraw_callback, self._layout_callback, self._callback_arg)
+            r = hierarchy_new(self._redraw_callback, self._layout_callback, self._callback_arg)
             r._parent = self
         end
         hierarchy_update(r, context, w._widget, w._width, w._height, region, w._matrix, matrix_to_device * w._matrix)
@@ -132,12 +132,12 @@ function hierarchy_update(self, context, widget, width, height, region, matrix_t
     -- Check which part needs to be redrawn
 
     -- Are there any children which were removed? Their area needs a redraw.
-    for _, h in ipairs(old_children) do
-        local x, y, width, height = matrix.transform_rectangle(h._matrix_to_device, h:get_draw_extents())
+    for _, child in ipairs(old_children) do
+        local x, y, w, h = matrix.transform_rectangle(child._matrix_to_device, child:get_draw_extents())
         region:union_rectangle(cairo.RectangleInt{
-            x = x, y = y, width = width, height = height
+            x = x, y = y, width = w, height = h
         })
-        h._parent = nil
+        child._parent = nil
     end
 
     -- Did we change and need to be redrawn?
@@ -167,7 +167,7 @@ end
 -- @param callback_arg A second argument that is given to the above callbacks.
 -- @return A new widget hierarchy
 function hierarchy.new(context, widget, width, height, redraw_callback, layout_callback, callback_arg)
-    local result = hierarchy_new(widget, redraw_callback, layout_callback, callback_arg)
+    local result = hierarchy_new(redraw_callback, layout_callback, callback_arg)
     result:update(context, widget, width, height)
     return result
 end
@@ -181,7 +181,7 @@ end
 -- @return A cairo region describing the changed parts (either the `region`
 --   argument or a new, internally created region).
 function hierarchy:update(context, widget, width, height, region)
-    local region = region or cairo.Region.create()
+    region = region or cairo.Region.create()
     hierarchy_update(self, context, widget, width, height, region, self._matrix, self._matrix_to_device)
     return region
 end
@@ -247,7 +247,7 @@ end
 
 --- Does the given cairo context have an empty clip (aka "no drawing possible")?
 local function empty_clip(cr)
-    local x, y, width, height = cr:clip_extents()
+    local _, _, width, height = cr:clip_extents()
     return width == 0 or height == 0
 end
 
diff --git a/lib/wibox/init.lua b/lib/wibox/init.lua
index f7bdfdc9..93f1cb2a 100644
--- a/lib/wibox/init.lua
+++ b/lib/wibox/init.lua
@@ -13,13 +13,8 @@ local capi = {
 local setmetatable = setmetatable
 local pairs = pairs
 local type = type
-local table = table
-local string_format = string.format
-local color = require("gears.color")
 local object = require("gears.object")
 local beautiful = require("beautiful")
-local surface = require("gears.surface")
-local cairo = require("lgi").cairo
 local base = require("wibox.widget.base")
 
 --- This provides widget box windows. Every wibox can also be used as if it were
@@ -82,15 +77,16 @@ for _, k in pairs{ "buttons", "struts", "geometry", "get_xproperty", "set_xprope
 end
 
 local function setup_signals(_wibox)
-    local w = _wibox.drawin
-
+    local obj
     local function clone_signal(name)
         _wibox:add_signal(name)
         -- When "name" is emitted on wibox.drawin, also emit it on wibox
-        w:connect_signal(name, function(_, ...)
+        obj:connect_signal(name, function(_, ...)
             _wibox:emit_signal(name, ...)
         end)
     end
+
+    obj = _wibox.drawin
     clone_signal("property::border_color")
     clone_signal("property::border_width")
     clone_signal("property::buttons")
@@ -104,14 +100,7 @@ local function setup_signals(_wibox)
     clone_signal("property::x")
     clone_signal("property::y")
 
-    local d = _wibox._drawable
-    local function clone_signal(name)
-        _wibox:add_signal(name)
-        -- When "name" is emitted on wibox.drawin, also emit it on wibox
-        d:connect_signal(name, function(_, ...)
-            _wibox:emit_signal(name, ...)
-        end)
-    end
+    obj = _wibox._drawable
     clone_signal("button::press")
     clone_signal("button::release")
     clone_signal("mouse::enter")
@@ -146,7 +135,7 @@ local function new(args)
     -- Add __tostring method to metatable.
     local mt = {}
     local orig_string = tostring(ret)
-    mt.__tostring = function(o)
+    mt.__tostring = function()
         return string.format("wibox: %s (%s)",
                              tostring(ret._drawable), orig_string)
     end
diff --git a/lib/wibox/layout/align.lua b/lib/wibox/layout/align.lua
index 95337aa8..069f4674 100644
--- a/lib/wibox/layout/align.lua
+++ b/lib/wibox/layout/align.lua
@@ -5,7 +5,6 @@
 -- @classmod wibox.layout.align
 ---------------------------------------------------------------------------
 
-local setmetatable = setmetatable
 local table = table
 local pairs = pairs
 local type = type
@@ -125,6 +124,7 @@ function align:layout(context, width, height)
                 x, y = size_first, 0
             end
         else
+            local _
             if self.dir == "y" then
                 _, h = base.fit_widget(self, context, self.second, width, size_second)
                 y = floor( (height - h)/2 )
@@ -192,7 +192,7 @@ function align:fit(context, orig_width, orig_height)
     local used_in_dir = 0
     local used_in_other = 0
 
-    for k, v in pairs{self.first, self.second, self.third} do
+    for _, v in pairs{self.first, self.second, self.third} do
         local w, h = base.fit_widget(self, context, v, orig_width, orig_height)
 
         local max = self.dir == "y" and w or h
@@ -233,7 +233,7 @@ function align:set_expand(mode)
 end
 
 function align:reset()
-    for k, v in pairs({ "first", "second", "third" }) do
+    for _, v in pairs({ "first", "second", "third" }) do
         self[v] = nil
     end
     self:emit_signal("widget::layout_changed")
diff --git a/lib/wibox/layout/constraint.lua b/lib/wibox/layout/constraint.lua
index 9fd4c1d2..99177c1b 100644
--- a/lib/wibox/layout/constraint.lua
+++ b/lib/wibox/layout/constraint.lua
@@ -14,7 +14,7 @@ local math = math
 local constraint = { mt = {} }
 
 --- Layout a constraint layout
-function constraint:layout(context, width, height)
+function constraint:layout(_, width, height)
     if self.widget then
         return { base.place_widget_at(self.widget, 0, 0, width, height) }
     end
@@ -62,14 +62,14 @@ end
 -- 'min' or 'exact'. Throws an error on invalid values.
 function constraint:set_strategy(val)
     local func = {
-        min = function(real_size, constraint)
-            return constraint and math.max(constraint, real_size) or real_size
+        min = function(real_size, limit)
+            return limit and math.max(limit, real_size) or real_size
         end,
-        max = function(real_size, constraint)
-            return constraint and math.min(constraint, real_size) or real_size
+        max = function(real_size, limit)
+            return limit and math.min(limit, real_size) or real_size
         end,
-        exact = function(real_size, constraint)
-            return constraint or real_size
+        exact = function(real_size, limit)
+            return limit or real_size
         end
     }
 
diff --git a/lib/wibox/layout/fixed.lua b/lib/wibox/layout/fixed.lua
index 0611effd..f2de84b8 100644
--- a/lib/wibox/layout/fixed.lua
+++ b/lib/wibox/layout/fixed.lua
@@ -22,7 +22,6 @@ function fixed:layout(context, width, height)
 
     for k, v in pairs(self.widgets) do
         local x, y, w, h, _
-        local in_dir
         if self.dir == "y" then
             x, y = 0, pos
             w, h = width, height - pos
@@ -30,7 +29,6 @@ function fixed:layout(context, width, height)
                 _, h = base.fit_widget(self, context, v, w, h);
             end
             pos = pos + h + spacing
-            in_dir = h
         else
             x, y = pos, 0
             w, h = width - pos, height
@@ -38,7 +36,6 @@ function fixed:layout(context, width, height)
                 w, _ = base.fit_widget(self, context, v, w, h);
             end
             pos = pos + w + spacing
-            in_dir = w
         end
 
         if (self.dir == "y" and pos-spacing > height) or
@@ -213,7 +210,7 @@ function fixed:fit(context, orig_width, orig_height)
     local width, height = orig_width, orig_height
     local used_in_dir, used_max = 0, 0
 
-    for k, v in pairs(self.widgets) do
+    for _, v in pairs(self.widgets) do
         local w, h = base.fit_widget(self, context, v, width, height)
         local in_dir, max
         if self.dir == "y" then
diff --git a/lib/wibox/layout/flex.lua b/lib/wibox/layout/flex.lua
index 9c0a4b54..4417ff7d 100644
--- a/lib/wibox/layout/flex.lua
+++ b/lib/wibox/layout/flex.lua
@@ -107,11 +107,7 @@ local flex = {}
 -- @name insert
 -- @class function
 
---- Layout a flex layout. Each widget gets an equal share of the available space.
--- @param context The context in which we are drawn.
--- @param width The available width.
--- @param height The available height.
-function flex:layout(context, width, height)
+function flex:layout(_, width, height)
     local result = {}
     local pos,spacing = 0, self._spacing
     local num = #self.widgets
@@ -128,7 +124,7 @@ function flex:layout(context, width, height)
         space_per_item = math.min(space_per_item, self._max_widget_size)
     end
 
-    for k, v in pairs(self.widgets) do
+    for _, v in pairs(self.widgets) do
         local x, y, w, h
         if self.dir == "y" then
             x, y = 0, util.round(pos)
@@ -163,7 +159,7 @@ function flex:fit(context, orig_width, orig_height)
     local sub_height = self.dir == "x" and orig_height or orig_height / #self.widgets
     local sub_width  = self.dir == "y" and orig_width  or orig_width / #self.widgets
 
-    for k, v in pairs(self.widgets) do
+    for _, v in pairs(self.widgets) do
         local w, h = base.fit_widget(self, context, v, sub_width, sub_height)
 
         local max = self.dir == "y" and w or h
diff --git a/lib/wibox/layout/margin.lua b/lib/wibox/layout/margin.lua
index e9b97e75..e7629a10 100644
--- a/lib/wibox/layout/margin.lua
+++ b/lib/wibox/layout/margin.lua
@@ -15,7 +15,7 @@ local cairo = require("lgi").cairo
 local margin = { mt = {} }
 
 --- Draw a margin layout
-function margin:draw(context, cr, width, height)
+function margin:draw(_, cr, width, height)
     local x = self.left
     local y = self.top
     local w = self.right
@@ -36,7 +36,7 @@ function margin:draw(context, cr, width, height)
 end
 
 --- Layout a margin layout
-function margin:layout(context, width, height)
+function margin:layout(_, width, height)
     if self.widget then
         local x = self.left
         local y = self.top
@@ -141,7 +141,7 @@ end
 -- @class function
 
 -- Create setters for each direction
-for k, v in pairs({ "left", "right", "top", "bottom" }) do
+for _, v in pairs({ "left", "right", "top", "bottom" }) do
     margin["set_" .. v] = function(layout, val)
         layout[v] = val
         layout:emit_signal("widget::layout_changed")
diff --git a/lib/wibox/layout/ratio.lua b/lib/wibox/layout/ratio.lua
index 201e1de6..baa9b2b4 100644
--- a/lib/wibox/layout/ratio.lua
+++ b/lib/wibox/layout/ratio.lua
@@ -10,7 +10,6 @@
 
 local base  = require("wibox.widget.base" )
 local flex  = require("wibox.layout.flex" )
-local fixed = require("wibox.layout.fixed")
 local table = table
 local pairs = pairs
 local floor = math.floor
@@ -125,21 +124,12 @@ local function normalize(self)
     assert(new_sum > 0.99 and new_sum < 1.01)
 end
 
---- Layout a ratio layout. Each widget gets a share of the size proportional
--- to its ratio
--- @param context The context in which we are drawn.
--- @tparam number width The available width.
--- @tparam number height The available height.
-function ratio:layout(context, width, height)
+function ratio:layout(_, width, height)
     local result = {}
     local pos,spacing = 0, self._spacing
-    local num = #self.widgets
-    local total_spacing = (spacing*(num-1))
-
-    --normalize(self)
 
     for k, v in ipairs(self.widgets) do
-        local space = nil
+        local space
         local x, y, w, h
 
         if self.dir == "y" then
@@ -179,8 +169,6 @@ function ratio:inc_ratio(index, increment)
         return
     end
 
-    local widget = self.widgets[index]
-
     assert(self._ratios[index])
 
     self:set_ratio(index, self._ratios[index] + increment)
@@ -214,7 +202,7 @@ function ratio:set_ratio(index, percent)
     -- Remove what has to be cleared from all widget
     local delta = ( (percent-old) / (#self.widgets-1) )
 
-    for k, v in pairs(self.widgets) do
+    for k in pairs(self.widgets) do
         self._ratios[k] = self._ratios[k] - delta
     end
 
diff --git a/lib/wibox/layout/rotate.lua b/lib/wibox/layout/rotate.lua
index 616d2564..8de9ef7b 100644
--- a/lib/wibox/layout/rotate.lua
+++ b/lib/wibox/layout/rotate.lua
@@ -25,7 +25,7 @@ local function transform(layout, width, height)
 end
 
 --- Layout this layout
-function rotate:layout(context, width, height)
+function rotate:layout(_, width, height)
     if not self.widget or not self.widget.visible then
         return
     end
diff --git a/lib/wibox/layout/scroll.lua b/lib/wibox/layout/scroll.lua
index d443a4a4..1af8f94e 100644
--- a/lib/wibox/layout/scroll.lua
+++ b/lib/wibox/layout/scroll.lua
@@ -6,14 +6,11 @@
 ---------------------------------------------------------------------------
 
 local cache = require("gears.cache")
-local color = require("gears.color")
-local matrix = require("gears.matrix")
 local timer = require("gears.timer")
 local hierarchy = require("wibox.hierarchy")
 local base = require("wibox.widget.base")
 local lgi = require("lgi")
 local GLib = lgi.GLib
-local cairo = lgi.cairo
 
 local scroll = {}
 local scroll_mt = { __index = scroll }
@@ -34,8 +31,7 @@ end
 -- Create a hierarchy (and some more stuff) for drawing the given widget. This
 -- allows "some stuff" to be re-used instead of re-created all the time.
 local hierarchy_cache = cache.new(function(context, widget, width, height)
-    local context = cleanup_context(context)
-    local surface = cairo.ImageSurface(cairo.Format.ARGB32, width, height)
+    context = cleanup_context(context)
     local layouts = setmetatable({}, { __mode = "k" })
 
     -- Create a widget hierarchy and update when needed
@@ -50,10 +46,10 @@ local hierarchy_cache = cache.new(function(context, widget, width, height)
             w:emit_signal(signal)
         end
     end
-    local function redraw_callback(h, arg)
+    local function redraw_callback()
         emit("widget::redraw_needed")
     end
-    local function layout_callback(h, arg)
+    local function layout_callback()
         emit("widget::redraw_needed")
         emit("widget::layout_changed")
     end
@@ -122,11 +118,11 @@ local function calculate_info(self, context, width, height)
         end
         result.first_x, result.first_y = x, y
         -- Was the extra space already included elsewhere?
-        local extra = self.expand and 0 or self.extra_space
+        local extra_spacer = self.expand and 0 or self.extra_space
         if self.dir == "h" then
-            x = x + surface_width + extra
+            x = x + surface_width + extra_spacer
         else
-            y = y + surface_height + extra
+            y = y + surface_height + extra_spacer
         end
         result.second_x, result.second_y = x, y
     else
@@ -135,10 +131,10 @@ local function calculate_info(self, context, width, height)
     result.surface_width, result.surface_height = surface_width, surface_height
 
     -- Get the hierarchy and subscribe ourselves to updates
-    local hier, do_pending_updates, context = hierarchy_cache:get(context,
+    local hier, do_pending_updates, ctx = hierarchy_cache:get(context,
             self.widget, surface_width, surface_height)
     result.hierarchy = hier
-    result.context = context
+    result.context = ctx
     do_pending_updates(self)
 
     return result
@@ -429,19 +425,19 @@ scroll.step_functions = {}
 
 --- A step function that scrolls the widget in an increasing direction with
 -- constant speed.
-function scroll.step_functions.linear_increase(elapsed, size, visible_size, speed, extra_space)
+function scroll.step_functions.linear_increase(elapsed, size, _, speed, extra_space)
     return (elapsed * speed) % (size + extra_space)
 end
 
 --- A step function that scrolls the widget in an decreasing direction with
 -- constant speed.
-function scroll.step_functions.linear_decrease(elapsed, size, visible_size, speed, extra_space)
+function scroll.step_functions.linear_decrease(elapsed, size, _, speed, extra_space)
     return (-elapsed * speed) % (size + extra_space)
 end
 
 --- A step function that scrolls the widget to its end and back to its
 -- beginning, then back to its end, etc. The speed is constant.
-function scroll.step_functions.linear_back_and_forth(elapsed, size, visible_size, speed, extra_space)
+function scroll.step_functions.linear_back_and_forth(elapsed, size, visible_size, speed)
     local state = ((elapsed * speed) % (2 * size)) / size
     state = state <= 1 and state or 2 - state
     return (size - visible_size) * state
@@ -450,7 +446,7 @@ end
 --- A step function that scrolls the widget to its end and back to its
 -- beginning, then back to its end, etc. The speed is null at the ends and
 -- maximal in the middle.
-function scroll.step_functions.nonlinear_back_and_forth(elapsed, size, visible_size, speed, extra_space)
+function scroll.step_functions.nonlinear_back_and_forth(elapsed, size, visible_size, speed)
     local state = ((elapsed * speed) % (2 * size)) / size
     local negate = false
     if state > 1 then
@@ -478,7 +474,7 @@ end
 --- A step function that scrolls the widget to its end and back to its
 -- beginning, then back to its end, etc. The speed is null at the ends and
 -- maximal in the middle. At both ends the widget stands still for a moment.
-function scroll.step_functions.waiting_nonlinear_back_and_forth(elapsed, size, visible_size, speed, extra_space)
+function scroll.step_functions.waiting_nonlinear_back_and_forth(elapsed, size, visible_size, speed)
     local state = ((elapsed * speed) % (2 * size)) / size
     local negate = false
     if state > 1 then
diff --git a/lib/wibox/layout/stack.lua b/lib/wibox/layout/stack.lua
index ec11febc..910270cb 100644
--- a/lib/wibox/layout/stack.lua
+++ b/lib/wibox/layout/stack.lua
@@ -18,7 +18,6 @@ local base  = require("wibox.widget.base" )
 local fixed = require("wibox.layout.fixed")
 local table = table
 local pairs = pairs
-local floor = math.floor
 local util  = require("awful.util")
 
 local stack = {mt={}}
@@ -97,15 +96,11 @@ local stack = {mt={}}
 -- @name set_spacing
 -- @class function
 
---- Layout a stack layout. Each widget get drawn on top of each other
--- @param context The context in which we are drawn.
--- @param width The available width.
--- @param height The available height.
-function stack:layout(context, width, height)
+function stack:layout(_, width, height)
     local result = {}
     local spacing = self._spacing
 
-    for k, v in pairs(self.widgets) do
+    for _, v in pairs(self.widgets) do
         table.insert(result, base.place_widget_at(v, spacing, spacing, width - 2*spacing, height - 2*spacing))
         if self._top_only then break end
     end
@@ -113,15 +108,11 @@ function stack:layout(context, width, height)
     return result
 end
 
---- Fit the stack layout into the given space
--- @param context The context in which we are fit.
--- @param orig_width The available width.
--- @param orig_height The available height.
 function stack:fit(context, orig_width, orig_height)
     local max_w, max_h = 0,0
     local spacing = self._spacing
 
-    for k, v in pairs(self.widgets) do
+    for _, v in pairs(self.widgets) do
         local w, h = base.fit_widget(self, context, v, orig_width, orig_height)
         max_w, max_h = math.max(max_w, w+2*spacing), math.max(max_h, h+2*spacing)
     end
diff --git a/lib/wibox/widget/background.lua b/lib/wibox/widget/background.lua
index 519059f2..274d8024 100644
--- a/lib/wibox/widget/background.lua
+++ b/lib/wibox/widget/background.lua
@@ -13,7 +13,7 @@ local cairo = require("lgi").cairo
 local setmetatable = setmetatable
 local pairs = pairs
 local type = type
-local unpack = unpack or table.unpack
+local unpack = unpack or table.unpack -- luacheck: globals unpack (compatibility with Lua 5.1)
 
 local background = { mt = {} }
 
@@ -55,7 +55,7 @@ function background:draw(context, cr, width, height)
 end
 
 -- Draw the border
-function background:after_draw_children(context, cr, width, height)
+function background:after_draw_children(_, cr)
     -- Draw the border
     if self._path and self._shape_border_width and self._shape_border_width > 0 then
         cr:append_path(self._path)
@@ -68,14 +68,14 @@ function background:after_draw_children(context, cr, width, height)
 end
 
 --- Prepare drawing the children of this widget
-function background:before_draw_children(context, cr, width, height)
+function background:before_draw_children(_, cr)
     if self.foreground then
         cr:set_source(self.foreground)
     end
 end
 
 --- Layout this widget
-function background:layout(context, width, height)
+function background:layout(_, width, height)
     if self.widget then
         return { base.place_widget_at(self.widget, 0, 0, width, height) }
     end
diff --git a/lib/wibox/widget/base.lua b/lib/wibox/widget/base.lua
index 00c25f8f..c528ad1d 100644
--- a/lib/wibox/widget/base.lua
+++ b/lib/wibox/widget/base.lua
@@ -85,13 +85,13 @@ end
 -- The default implementation does nothing, this must be re-implemented by
 -- all layout and container widgets.
 -- @tparam table children A table composed of valid widgets
-function base.widget:set_children(children)
+function base.widget:set_children(children) -- luacheck: no unused
     -- Nothing on purpose
 end
 
 -- It could have been merged into `get_all_children`, but it's not necessary
 local function digg_children(ret, tlw)
-    for k, w in ipairs(tlw:get_children()) do
+    for _, w in ipairs(tlw:get_children()) do
         table.insert(ret, w)
         digg_children(ret, w)
     end
@@ -122,9 +122,9 @@ function base.widget:index(widget, recursive, ...)
         if w == widget then
             return idx, self, {...}
         elseif recursive then
-            local idx, l, path = w:index(widget, true, self, ...)
-            if idx and l then
-                return idx, l, path
+            local child_idx, l, path = w:index(widget, true, self, ...)
+            if child_idx and l then
+                return child_idx, l, path
             end
         end
     end
@@ -206,8 +206,8 @@ function base.fit_widget(parent, context, widget, width, height)
     end
 
     -- Sanitize the input. This also filters out e.g. NaN.
-    local width = math.max(0, width)
-    local height = math.max(0, height)
+    width = math.max(0, width)
+    height = math.max(0, height)
 
     local w, h = 0, 0
     if widget.fit then
@@ -250,8 +250,8 @@ function base.layout_widget(parent, context, widget, width, height)
     end
 
     -- Sanitize the input. This also filters out e.g. NaN.
-    local width = math.max(0, width)
-    local height = math.max(0, height)
+    width = math.max(0, width)
+    height = math.max(0, height)
 
     if widget.layout then
         return get_cache(widget, "layout"):get(context, width, height)
@@ -261,6 +261,7 @@ end
 -- Handle a button event on a widget. This is used internally and should not be
 -- called directly.
 function base.handle_button(event, widget, x, y, button, modifiers, geometry)
+    x = x or y -- luacheck: no unused
     local function is_any(mod)
         return #mod == 1 and mod[1] == "Any"
     end
@@ -279,7 +280,7 @@ function base.handle_button(event, widget, x, y, button, modifiers, geometry)
 
     -- Find all matching button objects
     local matches = {}
-    for k, v in pairs(widget.widget_buttons) do
+    for _, v in pairs(widget.widget_buttons) do
         local match = true
         -- Is it the right button?
         if v.button ~= 0 and v.button ~= button then match = false end
@@ -291,7 +292,7 @@ function base.handle_button(event, widget, x, y, button, modifiers, geometry)
     end
 
     -- Emit the signals
-    for k, v in pairs(matches) do
+    for _, v in pairs(matches) do
         v:emit_signal(event,geometry)
     end
 end
@@ -332,7 +333,6 @@ end
 
 -- Read the table, separate attributes from widgets
 local function parse_table(t, leave_empty)
-    local keys= {}
     local max = 0
     local attributes, widgets = {}, {}
     for k,v in pairs(t) do
@@ -450,12 +450,12 @@ function base.make_widget_declarative(args)
     local w, id = drill(ids, args)
 
     local mt = {}
-    local orig_string = tostring(ret)
+    local orig_string = tostring(w)
 
     rawset(w, "_by_id", ids)
     rawset(w, "get_children_by_id", get_children_by_id)
 
-    mt.__tostring = function(o)
+    mt.__tostring = function()
         return string.format("%s (%s)", id, orig_string)
     end
 
@@ -518,7 +518,7 @@ function base.make_widget(proxy, widget_name)
         ret.fit = function(_, context, width, height)
             return base.fit_widget(ret, context, proxy, width, height)
         end
-        ret.layout = function(_, context, width, height)
+        ret.layout = function(_, _, width, height)
             return { base.place_widget_at(proxy, 0, 0, width, height) }
         end
         proxy:connect_signal("widget::layout_changed", function()
@@ -544,7 +544,7 @@ function base.make_widget(proxy, widget_name)
     ret.widget_name = widget_name or object.modulename(3)
     local mt = {}
     local orig_string = tostring(ret)
-    mt.__tostring = function(o)
+    mt.__tostring = function()
         return string.format("%s (%s)", ret.widget_name, orig_string)
     end
     return setmetatable(ret, mt)
@@ -559,7 +559,7 @@ end
 -- widget is not a valid widget.
 function base.check_widget(widget)
     assert(type(widget) == "table")
-    for k, func in pairs({ "add_signal", "connect_signal", "disconnect_signal" }) do
+    for _, func in pairs({ "add_signal", "connect_signal", "disconnect_signal" }) do
         assert(type(widget[func]) == "function", func .. " is not a function")
     end
 end
diff --git a/lib/wibox/widget/imagebox.lua b/lib/wibox/widget/imagebox.lua
index d30fe5e8..b617724c 100644
--- a/lib/wibox/widget/imagebox.lua
+++ b/lib/wibox/widget/imagebox.lua
@@ -10,14 +10,13 @@ local surface = require("gears.surface")
 local setmetatable = setmetatable
 local pairs = pairs
 local type = type
-local pcall = pcall
 local print = print
-local unpack = unpack or table.unpack
+local unpack = unpack or table.unpack -- luacheck: globals unpack (compatibility with Lua 5.1)
 
 local imagebox = { mt = {} }
 
 --- Draw an imagebox with the given cairo context in the given geometry.
-function imagebox:draw(context, cr, width, height)
+function imagebox:draw(_, cr, width, height)
     if not self._image then return end
     if width == 0 or height == 0 then return end
 
@@ -42,7 +41,7 @@ function imagebox:draw(context, cr, width, height)
 end
 
 --- Fit the imagebox into the given geometry
-function imagebox:fit(context, width, height)
+function imagebox:fit(_, width, height)
     if not self._image then
         return 0, 0
     end
@@ -81,8 +80,6 @@ end
 --   interpreted as the path to a png image file.
 -- @return true on success, false if the image cannot be used
 function imagebox:set_image(image)
-    local image = image
-
     if type(image) == "string" then
         image = surface.load(image)
         if not image then
diff --git a/lib/wibox/widget/systray.lua b/lib/wibox/widget/systray.lua
index e3ecdd04..262c274e 100644
--- a/lib/wibox/widget/systray.lua
+++ b/lib/wibox/widget/systray.lua
@@ -48,7 +48,7 @@ function systray:draw(context, cr, width, height)
                          base, is_rotated, bg, reverse, spacing)
 end
 
-function systray:fit(context, width, height)
+function systray:fit(_, width, height)
     local num_entries = capi.awesome.systray()
     local base = base_size
     local spacing = beautiful.systray_icon_spacing or 0
@@ -76,7 +76,7 @@ local function new(revers)
     ret.draw = systray.draw
     ret.set_base_size = function(_, size) base_size = size end
     ret.set_horizontal = function(_, horiz) horizontal = horiz end
-    ret.set_reverse = function(revers) reverse = revers end
+    ret.set_reverse = function(arg) reverse = arg end
 
     if revers then
         ret:set_reverse(true)
diff --git a/lib/wibox/widget/textbox.lua b/lib/wibox/widget/textbox.lua
index 241ba391..1159359a 100644
--- a/lib/wibox/widget/textbox.lua
+++ b/lib/wibox/widget/textbox.lua
@@ -10,13 +10,11 @@ local base = require("wibox.widget.base")
 local gdebug = require("gears.debug")
 local beautiful = require("beautiful")
 local lgi = require("lgi")
-local cairo = lgi.cairo
 local Pango = lgi.Pango
 local PangoCairo = lgi.PangoCairo
 local type = type
 local setmetatable = setmetatable
 local pairs = pairs
-local error = error
 
 local textbox = { mt = {} }
 
@@ -40,7 +38,7 @@ end
 function textbox:draw(context, cr, width, height)
     setup_layout(self, width, height, context.dpi)
     cr:update_layout(self._layout)
-    local ink, logical = self._layout:get_pixel_extents()
+    local _, logical = self._layout:get_pixel_extents()
     local offset = 0
     if self._valign == "center" then
         offset = (height - logical.height) / 2
@@ -52,7 +50,7 @@ function textbox:draw(context, cr, width, height)
 end
 
 local function do_fit_return(self)
-    local ink, logical = self._layout:get_pixel_extents()
+    local _, logical = self._layout:get_pixel_extents()
     if logical.width == 0 or logical.height == 0 then
         return 0, 0
     end
@@ -110,7 +108,7 @@ function textbox:get_height_for_width_at_dpi(width, dpi)
     setup_dpi(self, dpi)
     self._layout.width = Pango.units_from_double(width)
     self._layout.height = -max_lines -- show this many lines per paragraph
-    local w, h = do_fit_return(self)
+    local _, h = do_fit_return(self)
     return h
 end
 
@@ -261,7 +259,7 @@ local function new(text, ignore_markup)
     return ret
 end
 
-function textbox.mt:__call(...)
+function textbox.mt.__call(_, ...)
     return new(...)
 end
 
diff --git a/tests/_runner.lua b/tests/_runner.lua
index c07490fe..b954c539 100644
--- a/tests/_runner.lua
+++ b/tests/_runner.lua
@@ -1,7 +1,7 @@
 local timer = require("gears.timer")
 local awful = require("awful")
 
-runner = {
+local runner = {
   quit_awesome_on_error = os.getenv('TEST_PAUSE_ON_ERRORS') ~= '1',
   -- quit-on-timeout defaults to false: indicates some problem with the test itself.
   quit_awesome_on_timeout = os.getenv('TEST_QUIT_ON_TIMEOUT') ~= '1',
diff --git a/tests/test-benchmark.lua b/tests/test-benchmark.lua
index 0b09254c..ca35f171 100644
--- a/tests/test-benchmark.lua
+++ b/tests/test-benchmark.lua
@@ -15,7 +15,7 @@ do
     local timer_measure = GLib.Timer()
     measure = function(f, iter)
         timer_measure:start()
-        for i = 1, iter do
+        for _ = 1, iter do
             f()
         end
         local elapsed = timer_measure:elapsed()
@@ -47,7 +47,7 @@ local function create_and_draw_wibox()
     do_pending_repaint()
 end
 
-local wb, textclock = create_wibox()
+local _, textclock = create_wibox()
 
 local function relayout_textclock()
     textclock:emit_signal("widget::layout_changed")
diff --git a/tests/test-focus.lua b/tests/test-focus.lua
index bc8b8673..084be2fb 100644
--- a/tests/test-focus.lua
+++ b/tests/test-focus.lua
@@ -1,10 +1,9 @@
 --- Tests for focus signals / property.
 -- Test for https://github.com/awesomeWM/awesome/issues/134.
 
-awful = require("awful")
-timer = require("gears.timer")
+local awful = require("awful")
 
-beautiful = require("beautiful")
+local beautiful = require("beautiful")
 beautiful.border_normal = "#0000ff"
 beautiful.border_focus  = "#00ff00"
 
diff --git a/tests/test-leaks.lua b/tests/test-leaks.lua
index a7622fbd..e271bc55 100644
--- a/tests/test-leaks.lua
+++ b/tests/test-leaks.lua
@@ -3,17 +3,15 @@
 local awful = require("awful")
 local cairo = require("lgi").cairo
 local create_wibox = require("_wibox_helper").create_wibox
-local gears = require("gears")
 local wibox = require("wibox")
 
-local errors = {}
-
 local prepare_for_collect = nil
 local function emit_refresh()
     awesome.emit_signal("refresh")
 end
 
 -- Make the layoutbox in the default config GC'able
+-- luacheck: globals mywibox mylayoutbox
 mywibox[1].visible = false
 mywibox = nil
 mylayoutbox = nil
@@ -23,7 +21,7 @@ emit_refresh()
 local function collectable(a, b, c, d, e, f, g, h, last)
     assert(last == nil, "got more arguments than supported")
     local objs = setmetatable({ a, b, c, d, e, f, g, h }, { __mode = "v" })
-    a, b, c, d, e, f, g, h = nil, nil, nil, nil, nil, nil, nil, nil
+    a, b, c, d, e, f, g, h = nil, nil, nil, nil, nil, nil, nil, nil -- luacheck: ignore
     if prepare_for_collect then
         prepare_for_collect()
         prepare_for_collect = nil
@@ -31,7 +29,7 @@ local function collectable(a, b, c, d, e, f, g, h, last)
     collectgarbage("collect")
     collectgarbage("collect")
     -- Check if the table is now empty
-    for k, v in pairs(objs) do
+    for _, v in pairs(objs) do
         print("Some object was not garbage collected!")
         error(v)
     end
diff --git a/tests/test-spawn-snid.lua b/tests/test-spawn-snid.lua
index 8438cd19..27738fc2 100644
--- a/tests/test-spawn-snid.lua
+++ b/tests/test-spawn-snid.lua
@@ -16,7 +16,6 @@ local steps = {
     if count == 1 then
       ret, snid = spawn('urxvt', true)
     elseif manage_called then
-      local c = client.get()[1]
       assert(ret)
       assert(snid)
       assert(snid == c_snid)
diff --git a/tests/test-urgent.lua b/tests/test-urgent.lua
index 9e42727f..d51e256e 100644
--- a/tests/test-urgent.lua
+++ b/tests/test-urgent.lua
@@ -1,6 +1,10 @@
 --- Tests for urgent property.
 
-awful = require("awful")
+local awful = require("awful")
+local runner = require("_runner")
+
+-- This uses the global "tags" array set in the default config
+-- luacheck: globals tags
 
 -- Some basic assertion that the tag is not marked "urgent" already.
 assert(awful.tag.getproperty(tags[1][2], "urgent") == nil)
@@ -53,7 +57,7 @@ local steps = {
 
     elseif awful.tag.selectedlist()[1] == tags[1][2] then
       assert(#client.get() == 1)
-      c = client.get()[1]
+      local c = client.get()[1]
       assert(not c.urgent, "Client is not urgent anymore.")
       assert(c == client.focus, "Client is focused.")
       assert(awful.tag.getproperty(tags[1][2], "urgent") == false)
@@ -106,6 +110,6 @@ local steps = {
   end,
 }
 
-require("_runner").run_steps(steps)
+runner.run_steps(steps)
 
 -- vim: filetype=lua:expandtab:shiftwidth=4:tabstop=8:softtabstop=4:textwidth=80