Hammerspoon + Alacritty

alacritty.lua

-- Hammerspoon Spaces Management Library
-- https://github.com/asmagill/hs._asm.spaces
local spaces = require('hs.spaces')

local ALACRITTY_NAME = 'Alacritty'
local ALACRITTY_SELECTOR = 'org.alacritty'
local ALACRITTY_TOGGLE_FULLSCREEN_KEYBIND = {'cmd', 'return'}

-- Configuration options for the Alacritty script
local CONFIG = {
    WIDTH_SCALE = 0.9,
    HEIGHT_SCALE = 0.9,
    HIDE_ON_FOCUS_LOST = false,
}

-- Handle triggering the Alacritty application's fullscreen keybind
--
-- @param app The Alacritty application
function toggleAlacrittyFullscreen(app)
    hs.eventtap.keyStroke(table.unpack(ALACRITTY_TOGGLE_FULLSCREEN_KEYBIND), 0, app)
end

-- Handle moving the Alacritty application to the specified space and screen
--
-- @param app The Alacritty application
-- @param space The currently active space
-- @param screen The currently active screen
-- @param widthScale The desired width scaling factor for the application
-- @param heightScale The desired height scaling factor for the application
function moveAlacritty(app, space, screen, widthScale, heightScale)
    widthScale = widthScale or CONFIG['WIDTH_SCALE']
    heightScale = heightScale or CONFIG['HEIGHT_SCALE']

    -- Discover the provided application's main window
    -- Note the while-loop as calls to `mainWindow` could return `nil`
    local window = nil
    while window == nil do
        window = app:mainWindow()
    end

    if window:isFullscreen() then
        toggleAlacrittyFullscreen(app)
    end

    local windowFrame = window:frame()
    local screenFrame = screen:fullFrame()

    if not window:isFullscreen() then
        -- Scale the application's window according to the provided modifiers
        windowFrame.w = screenFrame.w * widthScale
        windowFrame.h = screenFrame.h * heightScale
        window:setFrame(windowFrame)

        -- Center the application on the current screen
        window:centerOnScreen(screen)
    end

    -- Attempt to move the application to the active space
    spaces.moveWindowToSpace(window, space)

    if window:isFullscreen() then
        toggleAlacrittyFullscreen(app)
    end
  
    -- Draw focus to the applications main window
    window:focus()
end

-- Handle toggling the visibility of the Alacritty application
function toggleAlacritty()
    local alacritty = hs.application.get(ALACRITTY_SELECTOR)

    if alacritty ~= nil and alacritty:isFrontmost() then
        -- If Alacritty is running and is the frontmost application, hide it
        alacritty:hide()
    else
        local focusedSpace = spaces.focusedSpace()
        local mainScreen = hs.screen.find(spaces.spaceDisplay(focusedSpace))

        -- If Alacritty is not running, attempt to launch the application
        if alacritty == nil and hs.application.launchOrFocus(ALACRITTY_NAME) then
            local appWatcher = nil
            appWatcher = hs.application.watcher.new(function (name, event, app)
                if event == hs.application.watcher.launched and name == ALACRITTY_NAME then
                    app:hide()
                    moveAlacritty(app, focusedSpace, mainScreen)
                    appWatcher:stop()
                end
            end)
            appWatcher:start()
        end

        if alacritty ~= nil then
            moveAlacritty(alacritty, focusedSpace, mainScreen)
        end
    end
end

-- Bind toggling the Alacritty application
hs.hotkey.bind({"alt"}, ".", toggleAlacritty)

-- Subscribe to events in order to hide the Alacritty application if focus is lost
if CONFIG['HIDE_ON_FOCUS_LOST'] then
    hs.window.filter.default:subscribe(hs.window.filter.windowUnfocused, function(window, app)
        local alacritty = hs.application.get(ALACRITTY_SELECTOR)
        if alacritty ~= nil then
            alacritty:hide()
        end
    end)
end

init.lua

require "alacritty"