window-configuration-change-hook

window-configuration-change-hook is a variable defined in `C source code'.
Its value is

(erc-window-configuration-change)

• This variable may be risky if used as a file-local variable.

Documentation:
Functions to call when window configuration changes.
The buffer-local part is run once per window, with the relevant window
selected; while the global part is run only once for the modified frame,
with the relevant frame selected.