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