WM_DEVMODECHANGE

  This message is sent to all top-level windows when the mode of an i/o
device changes. Currrently, the ToggleEGA() function will broadcast this
message when you switch between 25-line and 43/50-line modes, and lParam
will point to the string "SCREEN". Handling this message will give your
application the opportunity to resize various windows.

Parameters
  wParam is not used.
  lParam is a far pointer to the name of the device which has changed modes.