Graphics Programming Considerations ; of an error number. The code line is: TYPE $ERROR(IOSTAT(lun)) Managing Windows Windows can be: l Hidden (but not deleted) A hidden window is removed from the screen but not from graphics memory, and it can be retrieved at any time: FSET(glun) "/NODISPLAY" ;Hide a window FSET(glun) "/DISPLAY" ;Redisplay a window l Sent behind the parent's window stack: FSET(glun) "/STACK -1" l Brought to the front of the window stack: FSET(glun) "STACK 1" If you will not be reading events from a window, open it in write-only mode to save memory and processing time. Only the task that opened a window in read/write mode can read from it (monitor events).
Multiple tasks can write to an open window. A second task can write to an already open window by executing its own ATTACHand OPEN for the window. The logical units' numbers need not match, but the window name must be the same. If a task has the window Test open, other tasks can write to the window by: ATTACH(lun_1, 4) "GRAPHICS" FOPEN(lun_1) "Test /MAXSIZE 200 200 /WRITEONLY" eV+Language User's Guide, v2.x, 18318-000 Rev A Page 175