Module to apply a ManageHook to an already-mapped window when a property changes. This would commonly be used to match browser windows by title, since the final title will only be set after (a) the window is mapped, (b) its document has been loaded, (c) all load-time scripts have run. (Don't blame browsers for this; it's inherent in HTML and the DOM. And changing title dynamically is explicitly permitted by ICCCM and EWMH; you don't really want to have your editor window umapped/remapped to show the current document and modified state in the titlebar, do you?)

This is a handleEventHook that triggers on a PropertyChange event. It currently ignores properties being removed, in part because you can't do anything useful in a ManageHook involving nonexistence of a property.

This module could also be useful for Electron applications like Spotify which sets its WM_CLASS too late for window manager to map it properly.

You can use this module with the following in your xmonad.hs:

import XMonad.Hooks.OnPropertyChange

Enable it by including in you handleEventHook definition:

 main = xmonad $ def
     { ...
     , handleEventHook = onXPropertyChange "WM_NAME" (title =? "Spotify" --> doShift "5")
     , ...
     }

Or you could create a dynamicManageHook as below:

myDynamicManageHook :: ManageHook
myDynamicManageHook =
 composeAll
   [ className =? "Spotify" --> doShift (myWorkspaces !! 4),
     title =? "maybe_special_terminal" <||> title =? "special_terminal" --> doCenterFloat,
     className =? "dynamicApp" <&&> title =? "dynamic_app" --> doCenterFloat
   ]

And then use it in your handleEventHookDefinition:

 main = xmonad $ def
     { ...
     , handleEventHook = onXPropertyChange "WM_NAME" myDynamicManageHook
     , ...
     }