fgl_window_clear() clears the contents of a window even if it is not the current window. The function takes a window name as its argument, which can be any window that is open.
For example, if two windows are opened as follows:
OPEN WINDOW win1 AT 3,3 WITH 20 ROWS, 70 COLUMNS ATTRIBUTES(BORDER)
OPEN WINDOW win2 AT 6,10 WITH 10 ROWS, 60 COLUMNS ATTRIBUTES(BORDER)
Assuming both windows have contents, make win2 the current window as follows:
CURRENT WINDOW IS win2
Then clear the contents of win1:
fgl_window_clear("win1")
This would keep the window open and win2 would still be current, but the contents of win1 would have been erased.