_EXIT (function)
The _EXIT function prevents the user from closing a program and indicates if a user has clicked the close button in the window title (X button) or used CTRL + BREAK.
Contents
Syntax
- exitSignal% = _EXIT
Description
- Once the _EXIT function is used, the user can no longer manually exit the program until it is ended with END or SYSTEM.
- _EXIT returns any exit requests made after the initial call as:
- 0 = no exit request has been made since _EXIT monitoring began in the program.
- 1 = exit attempted by clicking the window X (close) button since last function call. (Bit 0 set)
- 2 = exit attempted with CTRL + BREAK since last call. (Bit 1 set)
- 3 = both CTRL + BREAK and the X box have been used since last call. (Bit 0 and 1 set)
- If a return value is not 0 the program can handle an exit request at a more convenient time if necessary.
- After being read, the _EXIT value is reset to 0 so store the value when a program delays an exit request.
- Note: Once _EXIT has been used once, you must monitor your program by checking it for user _EXIT requests.
- Don't just use _EXIT once to prevent a user from exiting a program early, as that constitutes bad practice.
Examples
Example 1: Using an ON TIMER check to read the _EXIT request return values.
q = _EXIT 'function read prevents any program exit at start of program ON TIMER(5) GOSUB quit TIMER ON PRINT " The Timer will check for exit request every 5 seconds." PRINT "Click the X box and/or Ctrl - Break to see the _EXIT return!" PRINT " Any Key Quits" PRINT DO: _LIMIT 30 ' ' simulated program loop LOOP UNTIL INKEY$ <> "" END quit: q = _EXIT IF q THEN PRINT q; SELECT CASE q CASE 1: PRINT "= X button was clicked" CASE 2: PRINT "= Ctrl + Break keypress" CASE 3: PRINT "= Both X and Ctrl + Break!" END SELECT RETURN
Example 2: Removing temporary files before closing a program upon a user's exit request.
x = _EXIT 'initial function call blocks a user exit OPEN "t3mpdata.tmp" FOR APPEND AS #1 DO IF _EXIT THEN CLOSE: KILL "t3mpdata.tmp": _DELAY 1: SYSTEM LOOP
See also
