Hammerspoon script to move/resize window under cursor

hammerspoon-move-resize.lua

-- Inspired by Linux alt-drag or Better Touch Tools move/resize functionality

function get_window_under_mouse()
  -- Invoke `hs.application` because `hs.window.orderedWindows()` doesn't do it
  -- and breaks itself
  local _ = hs.application

  local my_pos = hs.geometry.new(hs.mouse.getAbsolutePosition())
  local my_screen = hs.mouse.getCurrentScreen()

  return hs.fnutils.find(hs.window.orderedWindows(), function(w)
    return my_screen == w:screen() and my_pos:inside(w:frame())
  end)
end

dragging_win = nil
dragging_mode = 1

drag_event = hs.eventtap.new({ hs.eventtap.event.types.mouseMoved }, function(e)
  if dragging_win then
    local dx = e:getProperty(hs.eventtap.event.properties.mouseEventDeltaX)
    local dy = e:getProperty(hs.eventtap.event.properties.mouseEventDeltaY)
    local mods = hs.eventtap.checkKeyboardModifiers()

    -- Ctrl + Shift to move the window under cursor
    if dragging_mode == 1 and mods.ctrl and mods.shift then
      dragging_win:move({dx, dy}, nil, false, 0)

    -- Alt + Shift to resize the window under cursor
    elseif mods.alt and mods.shift then
      local sz = dragging_win:size()
      local w1 = sz.w + dx
      local h1 = sz.h + dy
      dragging_win:setSize(w1, h1)
    end
  end
  return nil
end)

flags_event = hs.eventtap.new({ hs.eventtap.event.types.flagsChanged }, function(e)
  local flags = e:getFlags()
  if flags.ctrl and flags.shift and dragging_win == nil then
    dragging_win = get_window_under_mouse()
    dragging_mode = 1
    drag_event:start()
  elseif flags.alt and flags.shift and dragging_win == nil then
    dragging_win = get_window_under_mouse()
    dragging_mode = 2
    drag_event:start()
  else
    drag_event:stop()
    dragging_win = nil
  end
  return nil
end)
flags_event:start()

Regarding slow FPS when resizing, check out this (closed) issue. Sounds like it needs to be fixed internally somehow: Hammerspoon/hammerspoon#923

Hey all,

I created a spoon that combines some of the techniques here and fixes the slow framerate while resizing:

https://github.com/dbalatero/SkyRocket.spoon

Instead of resizing the window in realtime, I draw an transparent preview box on the screen with hs.canvas, resize that as you drag, then commit the actual resize to the window when you let go of the mouse. It's a compromise for sure, but it's way better than dealing with the laggy framerate when naively trying to resize the window in realtime.

@dbalatero Thanks for the workaround - works like a charm!