simple_switcher.lua: simple mac window switcher with hammerspoon

_readme.md

simple_switcher.lua

I've been using numbered Spaces a lot more lately, and it's helpful for me to only see the apps/windows that I'm currently focused on, instead of all 30 apps I happen to have open. I wanted something similar to hs.window.switcher, but I don't care about window thumbnails and I wanted to be able to see more than just a few characters of the window title.

I cribbed heavily from the window_switcher.lua source but removed a lot of configurability, logging, backwards compatibility, and other good ideas.

Screencast/demo: (I have this new switcher bound to option+tab, and can still use the regular macos cmd-tab switcher)

init.lua

simple_switcher = require("simple_switcher")
switcher = simple_switcher.new({title_width = 1000, item_height = 32,})
local function mapAltTab(event)
   local flags = event:getFlags()
   local chars = event:getCharacters()
   if chars == "\t" and flags:containExactly{'alt'} then
      switcher:next()
      return true
   elseif chars == string.char(25) and flags:containExactly{'alt','shift'} then
      switcher:previous()
      return true
   end
end
tapAltTab = hs.eventtap.new({hs.eventtap.event.types.keyDown}, mapAltTab)
tapAltTab:start()

simple_switcher.lua

-- TODO: uses hs.window.filter right now but would it be better to watch window creation / deletion / space-moving / etc with hs.uielement.watcher and keep some internal table up to date with that?
-- TODO: notice when a window gets sent to another space and rebuild the window list

local hsdrawing = require('hs.drawing')
local hseventtap = require('hs.eventtap')
local hsgeom = require('hs.geometry')
local hsimage = require('hs.image')
local hsscreen = require('hs.screen')
local hstimer = require('hs.timer')

local min = math.min
local max = math.max
local checkMods = hseventtap.checkKeyboardModifiers
hs.window.animationDuration = 0
local UNAVAILABLE=hsimage.imageFromName('NSStopProgressTemplate')

local simple_switcher = {}

local icons=setmetatable({},{__mode='kv'})
local function getIcon(bundle)
   if not bundle then return UNAVAILABLE
   elseif not icons[bundle] then icons[bundle]=hsimage.imageFromAppBundle(bundle) or UNAVAILABLE end
   return icons[bundle]
end

local function rgba(r, g, b, a) return {red = r, green = g, blue = b, alpha = a} end
local function rgb(r, g, b, a) return rgba(r, g, b, 1) end

local function gc(self)
   self.screen_watcher:stop()
end

local function set_frames(nwindows, drawings, ui)
   if not drawings.screen_frame then
      drawings.screen_frame = hsscreen.mainScreen():frame()
   end
   local screen_frame = drawings.screen_frame
   local padding = ui.item_height * 0.1
   local size = min(
      ui.item_height,
      (screen_frame.h - padding*(nwindows+1))/nwindows
   )
   drawings.size = size
   -- TODO: pin to some corner (top-left) + padding, or center?
   -- TODO: expand in x to longest title?
   drawings.background = hsdrawing.rectangle(hsgeom(0,0,1,1))
   local bg_frame = hsgeom(0,0,
			   size+padding+ui.title_width+padding,
			   (size+padding)*nwindows+padding)
      :setcenter(screen_frame.center)
   drawings.background
      :setFillColor(ui.background_color)
      :setStroke(false)
      :setFrame(bg_frame)
      :setRoundedRectRadii(padding, padding)

   drawings.highlight_rect = hsdrawing.rectangle(hsgeom(0,0,1,1))
      :setFillColor(ui.highlight_color)
      :setStroke(false)
      :setRoundedRectRadii(padding, padding)

   local title_height = hsdrawing.getTextDrawingSize(
      'O', ui.title_text_style).h
   
   for i = 1,nwindows do
      local dr = drawings[i]
      local icon_frame = hsgeom(bg_frame.x, bg_frame.y, size, size)
	 :move(padding, padding + (size+padding)*(i-1))
      dr.icon:setFrame(icon_frame)
      dr.title_frame = hsgeom.copy(icon_frame)
	 :move(padding*2 + size, max(0,size - title_height)/2)
	 :setw(ui.title_width)
      local sel_frame = hsgeom.copy(icon_frame)
	 :setw(size + ui.title_width)
      dr.sel_frame = sel_frame
   end
end

local function show_selected(selected, drawings)
   local dr = drawings[selected]
   drawings.highlight_rect:setFrame(dr.sel_frame)
end

local function draw(windows, drawings, ui)
   drawings.background:show()
   drawings.highlight_rect:show()
   for i = 1,#windows do
      local win = windows[i]
      local dr = drawings[i]
      dr.icon:setImage(getIcon(win:application():bundleID())):show()
      local title = win:title() or ' '
      dr.title_text:setFrame(dr.title_frame)
      dr.title_text:setText(title):show()
   end
end

local MODS_INTERVAL=0.05 -- recheck for (lack of) mod keys after this interval
local function mods_pressed()
  local mods = checkMods(true)._raw
  return mods>0 and mods ~= 65536 -- caps lock
end

local function exit(self)
   local selected = self.selected
   local windows = self.windows
   local drawings = self.drawings
   local ui = self.ui
   self.windows = nil
   self.selected = nil
   self.modsTimer = nil
   drawings.background:hide()
   drawings.highlight_rect:hide()
   for i = 1,#windows do
      local dr = drawings[i]
      dr.icon:hide()
      dr.title_text:hide()
   end
   windows[selected]:focus()
end

local function show(self, direction)
   local windows = self.windows
   local drawings = self.drawings
   local ui = self.ui

   if not windows then
      windows = self.window_filter:getWindows(hs.window.filter.sortByFocusedLast)
      self.windows = windows
   end
   local nwindows = #windows or 0
   if nwindows == 0 then return end

   self.ui.title_text_style = {
      font = ui.font_name,
      size = ui.font_size,
      color = ui.text_color,
      lineBreak = 'truncateTail',
   }
   
   local selected = self.selected
   if not selected then
      local temp_frame = hsgeom(0,0,1,1)
      for n = 1,nwindows do
	 local dr = {}
	 dr.icon = hsdrawing.image(temp_frame, UNAVAILABLE)
	 dr.title_rect = hsdrawing.rectangle(temp_frame)
	    :setFillColor(ui.title_background_color)
	    :setStroke(false)
	 dr.title_text = hsdrawing.text(temp_frame, ' ')
	    :setTextStyle(self.ui.title_text_style)
	 drawings[n] = dr
      end
      set_frames(nwindows, drawings, ui)
      draw(windows, drawings, ui)
      selected = 1
      self.modsTimer = hstimer.waitWhile(
	 mods_pressed,
	 function() exit(self) end,
	 MODS_INTERVAL
      )
   end

   selected = selected + direction
   if selected <= 0 then
      selected = nwindows
   elseif selected > nwindows then
      selected = 1
   end
   self.selected = selected
   show_selected(selected, drawings)
end

function simple_switcher:next() return show(self, 1) end
function simple_switcher:previous() return show(self, -1) end

local ui_defaults = {
   text_color = rgb(1,1,1),
   font_name = "Monaco",
   font_size = 22,

   background_color = rgba(0.2, 0.2, 0.08, 0.8),
   highlight_color = rgba(0.6, 0.6, 0.3, 0.5),

   title_background_color = rgb(0,0,0),

   item_height = 64,
   title_width = 600,
   -- TODO: thumbnails
}

function simple_switcher.new(ui)
   if not ui then ui = {} end
   local self = setmetatable(
      {drawings={}},
      {__index=simple_switcher,__gc=gc}
   )
   self.window_filter = hs.window.filter.new():setCurrentSpace(true)
   self.drawings.screen_frame = nil
   self.screen_watcher = hs.screen.watcher.new(
      function() self.drawings.screen_frame = nil end
   ):start()
   self.ui = setmetatable(ui, {__index=ui_defaults})
   return self
end

return simple_switcher