---------------------------------------------------------------------------
--- Popup widget which shows current hotkeys and their descriptions.
--
-- It's easy to add hotkeys for your favorite application. Below is how to add
-- hotkeys for firefox to the previously created `hotkeys_popup` in `rc.lua`.
--
--    -- Create the rule that we will use to match for the application.
--    local fire_rule = { class = { "firefox", "Firefox" } }
--    for group_name, group_data in pairs({
--        ["Firefox: tabs"] = { color = "#009F00", rule_any = fire_rule }
--    }) do
--        hotkeys_popup.add_group_rules(group_name, group_data)
--    end
--
--    -- Table with all of our hotkeys
--    local firefox_keys = {
--
--        ["Firefox: tabs"] = {{
--            modifiers = { "Mod1" },
--            keys = {
--                ["1..9"] = "go to tab"
--            }
--        }, {
--            modifiers = { "Ctrl" },
--            keys = {
--                t = "new tab",
--                w = 'close tab',
--                ['Tab'] = "next tab"
--            }
--        }, {
--            modifiers = { "Ctrl", "Shift" },
--            keys = {
--              ['Tab'] = "previous tab"
--            }
--        }}
--    }
--
--    hotkeys_popup.add_hotkeys(firefox_keys)
--
--
-- Example of having different types of hotkey popups:
--
--    awful.keyboard.append_global_keybindings({
--        awful.key({modkey}, "/", function()
--          hotkeys_popup.show_help()
--        end, nil, {
--          description = "show help (all)", group="HELP"
--        }),
--        awful.key({"Shift", modkey}, "/", function()
--          hotkeys_popup.show_help(nil, nil, {show_awesome_keys=false})
--        end, nil, {
--          description = "show help for current app", group="HELP"
--        }),
--        awful.key({altkey, modkey}, "/", function()
--          hotkeys_popup.show_help({}, nil, {show_awesome_keys=true})
--        end, nil, {
--          description = "show help for awesome only", group="HELP"
--        })
--        -- (more hotkeys go here)
--    })
--
--
-- @author Yauheni Kirylau &lt;yawghen@gmail.com&gt;
-- @copyright 2014-2015 Yauheni Kirylau
-- @popupmod awful.hotkeys_popup.widget
---------------------------------------------------------------------------

local capi = {
    screen = screen,
    client = client,
}
local awful = require("awful")
local gtable = require("gears.table")
local gstring = require("gears.string")
local wibox = require("wibox")
local beautiful = require("beautiful")
local rgba = require("gears.color").to_rgba_string
local dpi = beautiful.xresources.apply_dpi

local matcher = require("gears.matcher")()

-- Stripped copy of this module https://github.com/copycat-killer/lain/blob/master/util/markup.lua:
local markup = {}
-- Set the font.
function markup.font(font, text)
    return '<span font="'    .. tostring(font)    .. '">' .. tostring(text) ..'</span>'
end
-- Set the foreground.
function markup.fg(color, text)
    return '<span foreground="' .. rgba(color, beautiful.fg_normal) .. '">' .. tostring(text) .. '</span>'
end
-- Set the background.
function markup.bg(color, text)
    return '<span background="' .. rgba(color, beautiful.bg_normal) .. '">' .. tostring(text) .. '</span>'
end

local function join_plus_sort(modifiers)
    if #modifiers<1 then return "none" end
    table.sort(modifiers)
    return table.concat(modifiers, '+')
end

local function get_screen(s)
    return s and capi.screen[s]
end


local widget = {
    group_rules = {},
}

--- Sort order for the hotkey modifiers
--
-- @tfield table awful.hotkeys_popup.widget.modifier_sort_order
-- @tfield int Alt Alt key priority
-- @tfield int Ctrl Ctrl key priority
-- @tfield int Shift Shift key priority
-- @tfield int Super Super key priority
--
-- @usage
-- To use change the sorting order for hotkey modifiers, add the following line
-- to your rc.lua file, after require("awful.hotkeys_popup"):
--
--     hotkeys_popup.widget.modifier_sort_order = {
--         Shift = 1,
--         Ctrl  = 2,
--         Super = 3,
--         Alt   = 4,
--     }
--
-- Setting 2 or more modifiers to the same number will cause their relative
-- sorting order to be undefined.
widget.modifier_sort_order = {
    Alt   = 1,
    Ctrl  = 2,
    Shift = 3,
    Super = 4,
}

--- Don't show hotkeys without descriptions.
-- @tfield boolean widget.hide_without_description
-- @param boolean
widget.hide_without_description = true

local function modifier_join_plus_sort(modifiers)
    if #modifiers<1 then return "none" end
    table.sort(modifiers, function(a,b)
            return widget.modifier_sort_order[a] < widget.modifier_sort_order[b]
        end)
    return table.concat(modifiers, '+')
end

--- Merge hotkey records into one if they have the same modifiers and
-- description. Records with five or more keys will abbreviate them.
--
-- This property only affects hotkey records added via `awful.key` keybindings.
-- Cheatsheets for external programs are static and will present merged records
-- regardless of the value of this property.
-- @tfield boolean widget.merge_duplicates
-- @param boolean
widget.merge_duplicates = true

--- Labels used for displaying human-readable keynames.
-- @tfield table awful.hotkeys_popup.widget.labels
-- @tfield[opt="Ctrl"] string Control
-- @tfield[opt="Alt"] string Mod1
-- @tfield[opt="Alt Gr"] string ISO_Level3_Shift
-- @tfield[opt="Super"] string Mod4
-- @tfield[opt="Ins"] string Insert
-- @tfield[opt="Del"] string Delete
-- @tfield[opt="PgDn"] string Next
-- @tfield[opt="PgUp"] string Prior
-- @tfield[opt="←"] string Left
-- @tfield[opt="↑"] string Up
-- @tfield[opt="→"] string Right
-- @tfield[opt="↓"] string Down
-- @tfield[opt="Num1"] string KP_End
-- @tfield[opt="Num2"] string KP_Down
-- @tfield[opt="Num3"] string KP_Next
-- @tfield[opt="Num4"] string KP_Left
-- @tfield[opt="Num5"] string KP_Begin
-- @tfield[opt="Num6"] string KP_Right
-- @tfield[opt="Num7"] string KP_Home
-- @tfield[opt="Num8"] string KP_Up
-- @tfield[opt="Num9"] string KP_Prior
-- @tfield[opt="Num0"] string KP_Insert
-- @tfield[opt="Num."] string KP_Delete
-- @tfield[opt="Num/"] string KP_Divide
-- @tfield[opt="Num*"] string KP_Multiply
-- @tfield[opt="Num-"] string KP_Subtract
-- @tfield[opt="Num+"] string KP_Add
-- @tfield[opt="NumEnter"] string KP_Enter
-- @tfield[opt="Esc"] string Escape
-- @tfield[opt="Tab"] string Tab
-- @tfield[opt="Space"] string space
-- @tfield[opt="Enter"] string Return
-- @tfield[opt="´"] string dead_acute
-- @tfield[opt="^"] string dead_circumflex
-- @tfield[opt="`"] string dead_grave
-- @tfield[opt="🔆+"] string XF86MonBrightnessUp
-- @tfield[opt="🔅-"] string XF86MonBrightnessDown
-- @tfield[opt="🕩+"] string XF86AudioRaiseVolume
-- @tfield[opt="🕩-"] string XF86AudioLowerVolume
-- @tfield[opt="🔇"] string XF86AudioMute
-- @tfield[opt="⏯"] string XF86AudioPlay
-- @tfield[opt="⏮"] string XF86AudioPrev
-- @tfield[opt="⏭"] string XF86AudioNext
-- @tfield[opt="⏹"] string XF86AudioStop
widget.labels = {
    Control          = "Ctrl",
    Mod1             = "Alt",
    ISO_Level3_Shift = "Alt Gr",
    Mod4             = "Super",
    Insert           = "Ins",
    Delete           = "Del",
    Next             = "PgDn",
    Prior            = "PgUp",
    Left             = "←",
    Up               = "↑",
    Right            = "→",
    Down             = "↓",
    KP_End           = "Num1",
    KP_Down          = "Num2",
    KP_Next          = "Num3",
    KP_Left          = "Num4",
    KP_Begin         = "Num5",
    KP_Right         = "Num6",
    KP_Home          = "Num7",
    KP_Up            = "Num8",
    KP_Prior         = "Num9",
    KP_Insert        = "Num0",
    KP_Delete        = "Num.",
    KP_Divide        = "Num/",
    KP_Multiply      = "Num*",
    KP_Subtract      = "Num-",
    KP_Add           = "Num+",
    KP_Enter         = "NumEnter",
    -- Some "obvious" entries are necessary for the Escape sequence
    -- and whitespace characters:
    Escape           = "Esc",
    Tab              = "Tab",
    space            = "Space",
    Return           = "Enter",
    -- Dead keys aren't distinct from non-dead keys because no sane
    -- layout should have both of the same kind:
    dead_acute       = "´",
    dead_circumflex  = "^",
    dead_grave       = "`",
    -- Basic multimedia keys:
    XF86MonBrightnessUp   = "🔆+",
    XF86MonBrightnessDown = "🔅-",
    XF86AudioRaiseVolume = "🕩+",
    XF86AudioLowerVolume = "🕩-",
    XF86AudioMute = "🔇",
    XF86AudioPlay = "⏯",
    XF86AudioPrev = "⏮",
    XF86AudioNext = "⏭",
    XF86AudioStop = "⏹",
}
--- Hotkeys widget background color.
-- @beautiful beautiful.hotkeys_bg
-- @tparam color hotkeys_bg

--- Hotkeys widget foreground color.
-- @beautiful beautiful.hotkeys_fg
-- @tparam color hotkeys_fg

--- Hotkeys widget border width.
-- @beautiful beautiful.hotkeys_border_width
-- @tparam int hotkeys_border_width

--- Hotkeys widget border color.
-- @beautiful beautiful.hotkeys_border_color
-- @tparam color hotkeys_border_color

--- Hotkeys widget shape.
-- @beautiful beautiful.hotkeys_shape
-- @tparam[opt] gears.shape hotkeys_shape
-- @see gears.shape

--- Foreground color used for hotkey modifiers (Ctrl, Alt, Super, etc).
-- @beautiful beautiful.hotkeys_modifiers_fg
-- @tparam color hotkeys_modifiers_fg

--- Background color used for miscellaneous labels of hotkeys widget.
-- @beautiful beautiful.hotkeys_label_bg
-- @tparam color hotkeys_label_bg

--- Foreground color used for hotkey groups and other labels.
-- @beautiful beautiful.hotkeys_label_fg
-- @tparam color hotkeys_label_fg

--- Override label background colors instead of cycling through xresources colors.
-- @beautiful beautiful.hotkeys_override_label_bgs
-- @tparam boolean hotkeys_override_label_bgs

--- Main hotkeys widget font.
-- @beautiful beautiful.hotkeys_font
-- @tparam string|lgi.Pango.FontDescription hotkeys_font

--- Font used for hotkeys' descriptions.
-- @beautiful beautiful.hotkeys_description_font
-- @tparam string|lgi.Pango.FontDescription hotkeys_description_font

--- Margin between hotkeys groups.
-- @beautiful beautiful.hotkeys_group_margin
-- @tparam int hotkeys_group_margin


--- Create an instance of widget with hotkeys help.
-- @tparam[opt] table args Configuration options for the widget.
-- @tparam[opt] boolean args.hide_without_description Don't show hotkeys without descriptions.
-- @tparam[opt] boolean args.merge_duplicates Merge hotkey records into one if
-- they have the same modifiers and description. Records with five keys or more
-- will abbreviate them.
-- @tparam[opt] int args.width Widget width.
-- @tparam[opt] int args.height Widget height.
-- @tparam[opt] color args.bg Widget background color.
-- @tparam[opt] color args.fg Widget foreground color.
-- @tparam[opt] int args.border_width Border width.
-- @tparam[opt] color args.border_color Border color.
-- @tparam[opt] gears.shape args.shape Widget shape.
-- @tparam[opt] string|lgi.Pango.FontDescription args.font Main widget font.
-- @tparam[opt] string|lgi.Pango.FontDescription args.description_font Font used for hotkeys' descriptions.
-- @tparam[opt] color args.modifiers_fg Foreground color used for hotkey
-- modifiers (Ctrl, Alt, Super, etc).
-- @tparam[opt] color args.label_bg Background color used for miscellaneous labels.
-- @tparam[opt] color args.label_fg Foreground color used for group and other
-- labels.
-- @tparam[opt] boolean args.override_label_bgs Override label background colors instead
-- of cycling through xresources colors.
-- @tparam[opt] int args.group_margin Margin between hotkeys groups.
-- @tparam[opt] table args.labels Labels used for displaying human-readable keynames.
-- @tparam[opt] table args.group_rules Rules for showing 3rd-party hotkeys. @see `awful.hotkeys_popup.keys.vim`.
-- @return Widget instance.
-- @constructorfct awful.widget.hotkeys_popup.widget.new
-- @usebeautiful beautiful.hotkeys_fg
-- @usebeautiful beautiful.hotkeys_bg
-- @usebeautiful beautiful.hotkeys_border_width
-- @usebeautiful beautiful.hotkeys_border_color
-- @usebeautiful beautiful.hotkeys_shape
-- @usebeautiful beautiful.hotkeys_modifiers_fg
-- @usebeautiful beautiful.hotkeys_label_bg
-- @usebeautiful beautiful.hotkeys_label_fg
-- @usebeautiful beautiful.hotkeys_override_label_bgs
-- @usebeautiful beautiful.hotkeys_font
-- @usebeautiful beautiful.hotkeys_description_font
-- @usebeautiful beautiful.hotkeys_group_margin
-- @usebeautiful beautiful.bg_normal Fallback.
-- @usebeautiful beautiful.fg_normal Fallback.
-- @usebeautiful beautiful.fg_minimize Fallback.
-- @usebeautiful beautiful.border_width Fallback.
function widget.new(args)
    args = args or {}
    local widget_instance = {
        hide_without_description = (
            args.hide_without_description == nil
        ) and widget.hide_without_description or args.hide_without_description,
        merge_duplicates = (
            args.merge_duplicates == nil
        ) and widget.merge_duplicates or args.merge_duplicates,
        group_rules = args.group_rules or gtable.clone(widget.group_rules),
        -- For every key in every `awful.key` binding, the first non-nil result
        -- in this lists is chosen as a human-readable name:
        -- * the value corresponding to its keysym in this table;
        -- * the UTF-8 representation as decided by awful.keyboard.get_key_name();
        -- * the keysym name itself;
        -- If no match is found, the key name will not be translated, and will
        -- be presented to the user as-is. (This is useful for cheatsheets for
        -- external programs.)
        labels = args.labels or widget.labels,
        _additional_hotkeys = {},
        _cached_wiboxes = {},
        _cached_awful_keys = {},
        _colors_counter = {},
        _group_list = {},
        _widget_settings_loaded = false,
        _keygroups = {},
    }
    for k, v in pairs(awful.key.keygroups) do
        widget_instance._keygroups[k] = {}
        for k2, v2 in pairs(v) do
            local keysym, keyprint = awful.keyboard.get_key_name(v2[1])
            widget_instance._keygroups[k][k2] =
                widget_instance.labels[keysym] or keyprint or keysym or v2[1]
        end
    end


    function widget_instance:_load_widget_settings()
        if self._widget_settings_loaded then return end
        self.width = args.width or dpi(1200)
        self.height = args.height or dpi(800)
        self.bg = args.bg or
            beautiful.hotkeys_bg or beautiful.bg_normal
        self.fg = args.fg or
            beautiful.hotkeys_fg or beautiful.fg_normal
        self.border_width = args.border_width or
            beautiful.hotkeys_border_width or beautiful.border_width
        self.border_color = args.border_color or
            beautiful.hotkeys_border_color or self.fg
        self.shape = args.shape or beautiful.hotkeys_shape
        self.modifiers_fg = args.modifiers_fg or
            beautiful.hotkeys_modifiers_fg or beautiful.bg_minimize or "#555555"
        self.label_bg = args.label_bg or
            beautiful.hotkeys_label_bg or self.fg
        self.label_fg = args.label_fg or
            beautiful.hotkeys_label_fg or self.bg
        self.override_label_bgs = args.override_label_bgs or
            beautiful.hotkeys_override_label_bgs or false
        self.opacity = args.opacity or
            beautiful.hotkeys_opacity or 1
        self.font = args.font or
            beautiful.hotkeys_font or "Monospace Bold 9"
        self.description_font = args.description_font or
            beautiful.hotkeys_description_font or "Monospace 8"
        self.group_margin = args.group_margin or
            beautiful.hotkeys_group_margin or dpi(6)
        self.label_colors = beautiful.xresources.get_current_theme()
        self._widget_settings_loaded = true
    end


    function widget_instance:_get_next_color(id)
        id = id or "default"
        if self._colors_counter[id] then
            self._colors_counter[id] = math.fmod(self._colors_counter[id] + 1, 15) + 1
        else
            self._colors_counter[id] = 1
        end
        return self.label_colors["color"..tostring(self._colors_counter[id], 15)]
    end


    function widget_instance:_add_hotkey(key, data, target)
        if self.hide_without_description and not data.description then return end

        local readable_mods = {}
        for _, mod in ipairs(data.mod) do
            table.insert(readable_mods, self.labels[mod] or mod)
        end
        local joined_mods = modifier_join_plus_sort(readable_mods)

        local group = data.group or "none"
        self._group_list[group] = true
        if not target[group] then target[group] = {} end
        local keysym, keyprint = awful.keyboard.get_key_name(key)
        local keylabel = self.labels[keysym] or keyprint or keysym or key
        local new_key = {
            key = keylabel,
            keylist = {keylabel},
            mod = joined_mods,
            description = data.description
        }
        local index = data.description or "none"  -- or use its hash?
        if not target[group][index] then
            target[group][index] = new_key
        else
            if self.merge_duplicates and joined_mods == target[group][index].mod then
                target[group][index].key = target[group][index].key .. "/" .. new_key.key
                table.insert(target[group][index].keylist, new_key.key)
            else
                while target[group][index] do
                    index = index .. " "
                end
                target[group][index] = new_key
            end
        end
    end


    function widget_instance:_sort_hotkeys(target)
        for group, _ in pairs(self._group_list) do
            if target[group] then
                local sorted_table = {}
                for _, key in pairs(target[group]) do
                    table.insert(sorted_table, key)
                end
                table.sort(
                    sorted_table,
                    function(a,b)
                        local k1, k2 = a.key or a.keys[1][1], b.key or b.keys[1][1]
                        return (a.mod or '')..k1<(b.mod or '')..k2 end
                )
                target[group] = sorted_table
            end
        end
    end


    function widget_instance:_abbreviate_awful_keys()
        -- This method is intended to abbreviate the keys of a merged entry (not
        -- the modifiers) if and only if the entry consists of five or more
        -- correlative keys from the same keygroup.
        --
        -- For simplicity, it checks only the first keygroup which contains the
        -- first key. If any of the keys in the merged entry is not in this
        -- keygroup, or there are any gaps between the keys (e.g. the entry
        -- contains the 2nd, 3rd, 5th, 6th, and 7th key in
        -- awful.key.keygroups.numrow, but not the 4th) this method does not try
        -- to abbreviate the entry.
        --
        -- Cheatsheets for external programs are abbreviated by hand where
        -- applicable: they do not need this method.
        for _, keys in pairs(self._cached_awful_keys) do
            for _, params in pairs(keys) do
                if #params.keylist > 4 then
                    -- assuming here keygroups will never overlap;
                    -- if they ever do, another for loop will be necessary:
                    local keygroup = gtable.find_first_key(self._keygroups, function(_, v)
                        return not not gtable.hasitem(v, params.keylist[1])
                    end)
                    local first, last, count, tally = nil, nil, 0, {}
                    for _, k in ipairs(params.keylist) do
                        local i = gtable.hasitem(self._keygroups[keygroup], k)
                        if i and not tally[i] then
                            tally[i] = k
                            if (not first) or (i < first) then first = i end
                            if (not last) or (i > last) then last = i end
                            count = count + 1
                        elseif not i then
                            count = 0
                            break
                        end
                    end
                    -- this conditional can only be true if there are more than
                    -- four actual keys (discounting duplicates) and ALL of
                    -- these keys can be found one after another in a keygroup:
                    if count > 4 and last - first + 1 == count then
                        params.key = tally[first] .. "…" .. tally[last]
                    end
                end
            end
        end
    end


    function widget_instance:_import_awful_keys()
        if next(self._cached_awful_keys) then
            return
        end
        for _, data in pairs(awful.key.hotkeys) do
            for _, key_pair in ipairs(data.keys) do
                self:_add_hotkey(key_pair[1], data, self._cached_awful_keys)
            end
        end
        self:_sort_hotkeys(self._cached_awful_keys)
        if self.merge_duplicates then
            self:_abbreviate_awful_keys()
        end
    end


    function widget_instance:_group_label(group, color)
        local bg_color = color
        if not bg_color then
            if self.override_label_bgs then
                bg_color = self.label_bg
            else
                bg_color = self.group_rules[group] and
                    self.group_rules[group].color or self:_get_next_color("group_title")
            end
        end
        local textbox = wibox.widget.textbox(
            markup.font(self.font,
                markup.bg(
                    bg_color,
                    markup.fg(self.label_fg, " "..group.." ")
                )
            )
        )
        local margin = wibox.container.margin()
        margin:set_widget(textbox)
        margin:set_top(self.group_margin)
        return margin
    end

    function widget_instance:_create_group_columns(column_layouts, group, keys, s, wibox_height)
        local line_height = math.max(
            beautiful.get_font_height(self.font),
            beautiful.get_font_height(self.description_font)
        )
        local group_label_height = line_height + self.group_margin
        -- -1 for possible pagination:
        local max_height_px = wibox_height - group_label_height

        local joined_descriptions = ""
        for i, key in ipairs(keys) do
            joined_descriptions = joined_descriptions .. key.description .. (i~=#keys and "\n" or "")
        end
        -- +1 for group label:
        local items_height = gstring.linecount(joined_descriptions) * line_height + group_label_height
        local current_column
        local available_height_px = max_height_px
        local add_new_column = true
        for i, column in ipairs(column_layouts) do
            if ((column.height_px + items_height) < max_height_px) or
                (i == #column_layouts and column.height_px < max_height_px / 2)
            then
                current_column = column
                add_new_column = false
                available_height_px = max_height_px - current_column.height_px
                break
            end
        end
        local overlap_leftovers
        if items_height > available_height_px then
            local new_keys = {}
            overlap_leftovers = {}
            -- +1 for group title and +1 for possible hyphen (v):
            local available_height_items = (available_height_px - group_label_height*2) / line_height
            for i=1,#keys do
                table.insert(((i<available_height_items) and new_keys or overlap_leftovers), keys[i])
            end
            keys = new_keys
            table.insert(keys, {key="▽", description=""})
        end
        if not current_column then
            current_column = {layout=wibox.layout.fixed.vertical()}
        end
        current_column.layout:add(self:_group_label(group))

        local function insert_keys(ik_keys, ik_add_new_column)
            local max_label_width = 0
            local joined_labels = ""
            for i, key in ipairs(ik_keys) do
                local modifiers = key.mod
                if not modifiers or modifiers == "none" then
                    modifiers = ""
                else
                    modifiers = markup.fg(self.modifiers_fg, modifiers.."+")
                end
                local key_label = ""
                if key.keylist and #key.keylist > 1 then
                    for each_key_idx, each_key in ipairs(key.keylist) do
                        key_label = key_label .. gstring.xml_escape(each_key)
                        if each_key_idx ~= #key.keylist then
                            key_label = key_label .. markup.fg(self.modifiers_fg, '/')
                        end
                    end
                elseif key.key then
                    key_label = gstring.xml_escape(key.key)
                end
                local rendered_hotkey = markup.font(self.font,
                    modifiers .. key_label .. " "
                ) .. markup.font(self.description_font,
                    key.description or ""
                )
                local label_width = wibox.widget.textbox.get_markup_geometry(rendered_hotkey, s).width
                if label_width > max_label_width then
                    max_label_width = label_width
                end
                joined_labels = joined_labels .. rendered_hotkey .. (i~=#ik_keys and "\n" or "")
                end
            current_column.layout:add(wibox.widget.textbox(joined_labels))
            local max_width = max_label_width + self.group_margin
            if not current_column.max_width or (max_width > current_column.max_width) then
                current_column.max_width = max_width
            end
            -- +1 for group label:
            current_column.height_px = (current_column.height_px or 0) +
                gstring.linecount(joined_labels)*line_height + group_label_height
            if ik_add_new_column then
                table.insert(column_layouts, current_column)
            end
        end

        insert_keys(keys, add_new_column)
        if overlap_leftovers then
            current_column = {layout=wibox.layout.fixed.vertical()}
            insert_keys(overlap_leftovers, true)
        end
    end

    function widget_instance:_create_wibox(s, available_groups, show_awesome_keys)
        s = get_screen(s)
        local wa = s.workarea
        local wibox_height = (self.height < wa.height) and self.height or
            (wa.height - self.border_width * 2)
        local wibox_width = (self.width < wa.width) and self.width or
            (wa.width - self.border_width * 2)

        -- arrange hotkey groups into columns
        local column_layouts = {}
        for _, group in ipairs(available_groups) do
            local keys = gtable.join(
                show_awesome_keys and self._cached_awful_keys[group] or nil,
                self._additional_hotkeys[group]
            )
            if #keys > 0 then
                self:_create_group_columns(column_layouts, group, keys, s, wibox_height)
            end
        end

        -- arrange columns into pages
        local available_width_px = wibox_width
        local pages = {}
        local columns = wibox.layout.fixed.horizontal()
        local previous_page_last_layout
        for _, item in ipairs(column_layouts) do
            if item.max_width > available_width_px then
                previous_page_last_layout:add(
                    self:_group_label("PgDn - Next Page", self.label_bg)
                )
                table.insert(pages, columns)
                columns = wibox.layout.fixed.horizontal()
                available_width_px = wibox_width - item.max_width
                item.layout:insert(
                    1, self:_group_label("PgUp - Prev Page", self.label_bg)
                )
            else
                available_width_px = available_width_px - item.max_width
            end
            local column_margin = wibox.container.margin()
            column_margin:set_widget(item.layout)
            column_margin:set_left(self.group_margin)
            columns:add(column_margin)
            previous_page_last_layout = item.layout
        end
        table.insert(pages, columns)

        -- Function to place the widget in the center and account for the
        -- workarea. This will be called in the placement field of the
        -- awful.popup constructor.
        local place_func = function(c)
            awful.placement.centered(c, {honor_workarea = true})
        end

        -- Construct the popup with the widget
        local mypopup = awful.popup {
            widget = pages[1],
            ontop = true,
            bg=self.bg,
            fg=self.fg,
            opacity = self.opacity,
            border_width = self.border_width,
            border_color = self.border_color,
            shape = self.shape,
            placement = place_func,
            minimum_width = wibox_width,
            minimum_height = wibox_height,
            screen = s,
        }

        local widget_obj = {
            current_page = 1,
            popup = mypopup,
        }

        -- Set up the mouse buttons to hide the popup
        -- Any keybinding except what the keygrabber wants wil hide the popup
        -- too
        mypopup.buttons = {
            awful.button({ }, 1, function () widget_obj:hide() end),
            awful.button({ }, 3, function () widget_obj:hide() end)
        }

        function widget_obj.page_next(w_self)
            if w_self.current_page == #pages then return end
            w_self.current_page = w_self.current_page + 1
            w_self.popup:set_widget(pages[w_self.current_page])
        end
        function widget_obj.page_prev(w_self)
            if w_self.current_page == 1 then return end
            w_self.current_page = w_self.current_page - 1
            w_self.popup:set_widget(pages[w_self.current_page])
        end
        function widget_obj.show(w_self)
            w_self.popup.visible = true
        end
        function widget_obj.hide(w_self)
            w_self.popup.visible = false
            if w_self.keygrabber then
                awful.keygrabber.stop(w_self.keygrabber)
            end
        end

        return widget_obj
    end


    --- Show popup with hotkeys help.
    -- @tparam[opt=client.focus] client c Client.
    -- @tparam[opt=c.screen] screen s Screen.
    -- @tparam[opt={}] table show_args Additional arguments.
    -- @tparam[opt=true] boolean show_args.show_awesome_keys Show AwesomeWM hotkeys.
    -- When set to `false` only app-specific hotkeys will be shown.
    -- @treturn awful.keygrabber The keybrabber used to detect when the key is
    --  released.
    -- @method show_help
    function widget_instance:show_help(c, s, show_args)
        show_args = show_args or {}
        local show_awesome_keys = show_args.show_awesome_keys ~= false

        self:_import_awful_keys()
        self:_load_widget_settings()

        c = c or capi.client.focus
        s = s or (c and c.screen or awful.screen.focused())

        local available_groups = {}
        for group, _ in pairs(self._group_list) do
            local need_match
            for group_name, data in pairs(self.group_rules) do
                if group_name==group and (
                    data.rule or data.rule_any or data.except or data.except_any
                ) then
                    if not c or not matcher:matches_rule(c, {
                        rule=data.rule,
                        rule_any=data.rule_any,
                        except=data.except,
                        except_any=data.except_any
                    }) then
                        need_match = true
                        break
                    end
                end
            end
            if not need_match then table.insert(available_groups, group) end
        end

        local joined_groups = join_plus_sort(available_groups)..tostring(show_awesome_keys)
        if not self._cached_wiboxes[s] then
            self._cached_wiboxes[s] = {}
        end
        if not self._cached_wiboxes[s][joined_groups] then
            self._cached_wiboxes[s][joined_groups] = self:_create_wibox(s, available_groups, show_awesome_keys)
        end
        local help_wibox = self._cached_wiboxes[s][joined_groups]
        help_wibox:show()

        help_wibox.keygrabber = awful.keygrabber.run(function(_, key, event)
            if event == "release" then return end
            if key then
                if key == "Next" then
                    help_wibox:page_next()
                elseif key == "Prior" then
                    help_wibox:page_prev()
                else
                    help_wibox:hide()
                end
            end
        end)
        return help_wibox.keygrabber
    end

    --- Add hotkey descriptions for third-party applications.
    -- @tparam table hotkeys Table with bindings,
    -- see `awful.hotkeys_popup.key.vim` as an example.
    -- @noreturn
    -- @method add_hotkeys
    function widget_instance:add_hotkeys(hotkeys)
        for group, bindings in pairs(hotkeys) do
            for _, binding in ipairs(bindings) do
                local modifiers = binding.modifiers
                local keys = binding.keys
                for key, description in pairs(keys) do
                    self:_add_hotkey(key, {
                        mod=modifiers,
                        description=description,
                        group=group},
                    self._additional_hotkeys
                )
                end
            end
        end
        self:_sort_hotkeys(self._additional_hotkeys)
    end

    --- Add hotkey group rules for third-party applications.
    -- @tparam string group Hotkeys group name,
    -- @tparam table data Rule data for the group
    -- see `awful.hotkeys_popup.key.vim` as an example.
    -- @noreturn
    -- @method add_group_rules
    function widget_instance:add_group_rules(group, data)
        self.group_rules[group] = data
    end

    return widget_instance
end

local function get_default_widget()
    if not widget.default_widget then
        widget.default_widget = widget.new()
    end
    return widget.default_widget
end

--- Show popup with hotkeys help (default widget instance will be used).
-- @tparam[opt] client c Client.
-- @tparam[opt] screen s Screen.
-- @tparam[opt] table args Additional arguments.
-- @tparam[opt=true] boolean args.show_awesome_keys Show AwesomeWM hotkeys.
-- When set to `false` only app-specific hotkeys will be shown.
-- @treturn awful.keygrabber The keybrabber used to detect when the key is
--  released.
-- @staticfct awful.hotkeys_popup.widget.show_help
function widget.show_help(...)
    return get_default_widget():show_help(...)
end

--- Add hotkey descriptions for third-party applications
-- (default widget instance will be used).
-- @tparam table hotkeys Table with bindings,
-- see `awful.hotkeys_popup.key.vim` as an example.
-- @noreturn
-- @staticfct awful.hotkeys_popup.widget.add_hotkeys
function widget.add_hotkeys(...)
    get_default_widget():add_hotkeys(...)
end

--- Add hotkey group rules for third-party applications
-- (default widget instance will be used).
-- @tparam string group Rule group name,
-- @tparam table data Rule data for the group
-- see `awful.hotkeys_popup.key.vim` as an example.
-- @noreturn
-- @staticfct awful.hotkeys_popup.widget.add_group_rules
function widget.add_group_rules(group, data)
    get_default_widget():add_group_rules(group, data)
end

return widget

-- vim: filetype=lua:expandtab:shiftwidth=4:tabstop=8:softtabstop=4:textwidth=80
