#!/bin/python

import i3ipc

transparency_val = '0.8';
ipc = i3ipc.Connection()
prev_focused = None
prev_workspace = ipc.get_tree().find_focused().workspace().num

for window in ipc.get_tree():
    if window.focused:
        prev_focused = window
    else:
        window.command('opacity ' + transparency_val)

def on_window_focus(ipc, event):
    global prev_focused
    global prev_workspace

    focused = event.container
    wo =  ipc.get_tree().find_focused()
    if wo == None:
        return
    workspace = wo.workspace().num

    if focused.id != prev_focused.id:
        focused.command('opacity 1')
        if workspace == prev_workspace:
            prev_focused.command('opacity ' + transparency_val)
        prev_focused = focused
        prev_workspace = workspace

ipc.on("window::focus", on_window_focus)
ipc.main()