How to Manage Windows Using Hammerspoon

Intro

I found that the windows management built in macOS is difficult to use. As a result, I always using my mouse to move and resize my window, which is less efficient. We should keep our hands on the keyboard as much as possible. After finishing the MIT-Missing-Semester, I came across the hammerspoon tool. I really like this one :)

What is hammerspoon ?

According to the official site’s introduction, hammerspoon is a tool for powerful automation of OS X, which is just a bridge between the operating system and a Lua scripting engine. The windows management is kind of automation.

To be honest, I once heard the Lua language but I don’t know anything about it. I follow Learn Lua in Y minutes to have a basic understanding of this language.

How to manage windows ?

I would like to have the following features:

1. Move and resize my window to the left/right of screen.
2. The full screen mode
3. Move and resize my window to the top-left/top-right/bottom-left/bottom-right of screen
4. Move current window to the center of screen

My solution consists of 3 *.lua file(I have put this in my dotfiles)

👉config.lua

MACBOOK_MONITOR = 'Built-in Retina Display'

-- disable animations, default value = 0.2
hs.window.animationDuration = 0

👉init.lua

require('config')
require('window')

👉window.lua

This is the main part of windows management.

-- half of screen
-- {frame.x, frame.y, window.w, window.h}
-- First two elements: we decide the position of frame
-- Last two elements: we decide the size of frame
hs.hotkey.bind({'alt', 'cmd'}, 'left', function() hs.window.focusedWindow():moveToUnit({0, 0, 0.5, 1}) end)
hs.hotkey.bind({'alt', 'cmd'}, 'right', function() hs.window.focusedWindow():moveToUnit({0.5, 0, 0.5, 1}) end)
hs.hotkey.bind({'alt', 'cmd'}, 'up', function() hs.window.focusedWindow():moveToUnit({0, 0, 1, 0.5}) end)
hs.hotkey.bind({'alt', 'cmd'}, 'down', function() hs.window.focusedWindow():moveToUnit({0, 0.5, 1, 0.5}) end)

-- quarter of screen
--[[
    u i
    j k
--]]
hs.hotkey.bind({'ctrl', 'alt', 'cmd'}, 'u', function() hs.window.focusedWindow():moveToUnit({0, 0, 0.5, 0.5}) end)
hs.hotkey.bind({'ctrl', 'alt', 'cmd'}, 'k', function() hs.window.focusedWindow():moveToUnit({0.5, 0.5, 0.5, 0.5}) end)
hs.hotkey.bind({'ctrl', 'alt', 'cmd'}, 'i', function() hs.window.focusedWindow():moveToUnit({0.5, 0, 0.5, 0.5}) end)
hs.hotkey.bind({'ctrl', 'alt', 'cmd'}, 'j', function() hs.window.focusedWindow():moveToUnit({0, 0.5, 0.5, 0.5}) end)


-- full screen
hs.hotkey.bind({'alt', 'cmd'}, 'f', function() hs.window.focusedWindow():moveToUnit({0, 0, 1, 1}) end)

-- center screen
hs.hotkey.bind({'alt', 'cmd'}, 'c', function() hs.window.focusedWindow():centerOnScreen() end)

You shoule put these files in ~/.hammerspoon/ and then click on Reload config 🤗

Code Explained

• hs.hotkey.bind(mods, key, pressedfn)
  • This is a simple function to create a new hotkey and bind it to pressedfn.
  • We press and hold mods and use key to enable pressedfn. For example, If we want to make a window full screen. We first press and hold alt(option) and cmd, then we press f.
• pressedfn
  • This is an anonymous function in Lua.
  • The key of this function is hs.window.focusedWindow():moveToUnit({...}). Its job is get the focused window and make some changes of position and size. The parameters are a table in Lua. You may combine the previous comments in window.lua and the image below to understand this.

Ref

1. Anish’s Hammerspoon config