feat(dock): initial dock implementation

This commit is more a showcase to demonstrate how we can use the slot
package to build custom UI. It includes a minimal UPower service and
slot's parameters binding and reusable UI modules.

I feel like this is going the right direction. We still have some
improvement margin, but the code is well separated in layers. We can
easily connect to the service in different contexts.

src/awesomerc/init.lua

@@ -59,6 +59,37 @@ slot {
    slot = my_slots.build_desktop_decoration,
 }
 
+---------
+-- Minimum code example to create a UPower service
+local lgi = require "lgi"
+local upower = lgi.require "UPowerGlib"
+local gears = require "gears"
+
+local function create_upower_service()
+   local service = gears.object()
+   service.device = upower.Client():get_display_device()
+   service.device.on_notify = function(d)
+      service:emit_signal("upower::update", d)
+   end
+   gears.timer.delayed_call(service.emit_signal, service, "upower::update", service.device)
+   return service
+end
+
+local upower_service = create_upower_service()
+---------
+-- Load the dock module
+local dock = require "awesomerc.slots.dock"
+
+slot {
+   target = capi.screen,
+   signal = "request::desktop_decoration",
+   slot = dock.create_desktop_decoration,
+   slot_params = {
+      upower_service = upower_service,
+   },
+}
+---------
+
 slot {
    target = capi.client,
    signal = "request::default_mousebindings",

src/awesomerc/slots/dock.lua

@@ -0,0 +1,47 @@
+local battery_widget = require "awesomerc.ui.battery-widget"
+local box = require "awesomerc.ui.box"
+local slot = require "awesome-slot"
+local ui_dock = require "awesomerc.ui.dock"
+local wibox = require "wibox"
+
+local dock = {}
+
+function dock.create_desktop_decoration(params)
+   local upower_service = params.upower_service
+
+   local battery = battery_widget()
+   slot {
+      target = upower_service,
+      signal = "upower::update",
+      slot = function()
+         return function(_, device)
+            battery.battery = device.percentage
+         end
+      end,
+   }
+
+   return function(screen)
+      screen.dock = ui_dock {
+         screen = screen,
+         left_widget = {
+            box {
+               screen = screen,
+               bg = "#FF0000",
+               fg = "#FFFFFF",
+               widget = battery,
+            },
+            layout = wibox.layout.fixed.horizontal,
+         },
+         middle_widget = {
+            markup = "<b>middle</b>",
+            widget = wibox.widget.textbox,
+         },
+         right_widget = {
+            markup = "<b>right</b>",
+            widget = wibox.widget.textbox,
+         },
+      }
+   end
+end
+
+return dock

src/awesomerc/ui/battery-widget.lua

@@ -0,0 +1,22 @@
+local gears = require "gears"
+local wibox = require "wibox"
+
+local battery_widget = {}
+
+function battery_widget:set_battery(percentage)
+   self.markup = percentage
+end
+
+function battery_widget.create()
+   local self = wibox.widget {
+      widget = wibox.widget.textbox,
+   }
+
+   return gears.table.crush(self, battery_widget)
+end
+
+return setmetatable(battery_widget, {
+   __call = function(_)
+      return battery_widget.create()
+   end,
+})

src/awesomerc/ui/box.lua

@@ -0,0 +1,45 @@
+local background = require "wibox.container.background"
+local beautiful = require "beautiful"
+local margin = require "wibox.container.margin"
+local shape = require "gears.shape"
+local widget = require "wibox.widget"
+
+local abs = math.abs
+local dpi = beautiful.xresources.apply_dpi
+
+local box = {}
+
+-- 10 is an arbitrary value I found after some tests :shrug:
+local CIRCLE_TO_BAR_THRESHOLD = 10
+
+function box.shape(cr, width, height)
+   local s = abs(width - height) > CIRCLE_TO_BAR_THRESHOLD and shape.rounded_bar or shape.circle
+
+   return s(cr, width, height)
+end
+
+function box.new(args)
+   local box_widget = widget {
+      {
+         widget = margin,
+         draw_empty = false,
+         top = dpi(beautiful.bar_box_padding_y, args.screen),
+         bottom = dpi(beautiful.bar_box_padding_y, args.screen),
+         right = dpi(beautiful.bar_box_padding_x, args.screen),
+         left = dpi(beautiful.bar_box_padding_x, args.screen),
+         args.widget,
+      },
+      bg = args.bg,
+      fg = args.fg,
+      shape = box.shape,
+      widget = background,
+   }
+
+   return box_widget
+end
+
+return setmetatable(box, {
+   __call = function(_, ...)
+      return box.new(...)
+   end,
+})

src/awesomerc/ui/dock.lua

@@ -0,0 +1,38 @@
+local beautiful = require "beautiful"
+local wibar = require "awful.wibar"
+local wibox = require "wibox"
+
+local dpi = beautiful.xresources.apply_dpi
+
+local dock = {}
+
+function dock.new(args)
+   local self = wibar {
+      screen = args.screen,
+      position = "top",
+      height = dpi(beautiful.bar_height, args.screen),
+      width = beautiful.bar_width, -- Width is a percentage of the screen size
+      margins = {
+         top = dpi(4),
+         bottom = dpi(4),
+         left = dpi(4),
+         right = dpi(4),
+      },
+      bg = "#000000",
+      fg = "#FFFFFF",
+      widget = {
+         args.left_widget,
+         args.middle_widget,
+         args.right_widget,
+         layout = wibox.layout.align.horizontal,
+      },
+   }
+
+   return self
+end
+
+return setmetatable(dock, {
+   __call = function(_, ...)
+      return dock.new(...)
+   end,
+})