Difference between revisions of "EXIT (function)"

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The '''_EXIT''' function indicates if a program user has used the close X button or CTRL + BREAK.
{{DISPLAYTITLE:_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.




{{PageSyntax}}
:{{Parameter|exitSignal%}} = [[_EXIT]]


* Once the function is called, the program user can no longer manually exit the program.
 
* _EXIT returns:
{{PageDescription}}
:: 0 - no exit request made
* Once the [[_EXIT]] function is used, the user can no longer manually exit the program until it is ended with [[END]] or [[SYSTEM]].
:: 1 - exit attempted by clicking the window X (close) box since last function call
* [[_EXIT]] returns any exit requests made after the initial call as:
:: 2 - exit attempted with CTRL + BREAK since last call
:: 0 = no exit request has been made since _EXIT monitoring began in the program.
:: 3 - both CTRL+BREAK and the X box have been used since last call
:: 1 = exit attempted by clicking the window X (close) button since last function call. (Bit 0 set)
* The program can later handle an exit request at a more convenient time
:: 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.
 
 
{{PageExamples}}
''Example 1:'' Using an ON TIMER check to read the _EXIT request return values.
{{CodeStart}} '' ''
q = {{Cl|_EXIT (function)|_EXIT}} 'function read prevents any program exit at start of program
{{Cl|ON TIMER (n)|ON TIMER}}(5) {{Cl|GOSUB}} quit
{{Cl|TIMER}} ON
{{Cl|PRINT}} "  The Timer will check for exit request every 5 seconds."
{{Cl|PRINT}} "Click the X box and/or Ctrl - Break to see the {{Cl|_EXIT (function)|_EXIT}} return!"
{{Cl|PRINT}} "                    Any Key Quits"
{{Cl|PRINT}}
{{Cl|DO}}: {{Cl|_LIMIT}} 30
  '                    ' simulated program loop
{{Cl|LOOP}} {{Cl|UNTIL}} {{Cl|INKEY$}} <> ""
{{Cl|END}}
 
quit:
q = {{Cl|_EXIT (function)|_EXIT}}
{{Cl|IF}} q {{Cl|THEN}} {{Cl|PRINT}} q;
{{Cl|SELECT CASE}} q
  {{Cl|CASE}} 1: {{Cl|PRINT}} "= X button was clicked"
  {{Cl|CASE}} 2: {{Cl|PRINT}} "= Ctrl + Break keypress"
  {{Cl|CASE}} 3: {{Cl|PRINT}} "= Both X and Ctrl + Break!"
{{Cl|END SELECT}}
{{Cl|RETURN}} '' ''
 
{{CodeEnd}}
 
 
''Example 2:'' Removing temporary files before closing a program upon a user's exit request.
{{CodeStart}} '' ''
x = {{Cl|_EXIT}}  'initial function call blocks a user exit
OPEN "t3mpdata.tmp" FOR APPEND AS #1
DO
IF {{Cl|_EXIT}} THEN {{Cl|CLOSE}}: {{Cl|KILL}} "t3mpdata.tmp": {{Cl|_DELAY}} 1: {{Cl|SYSTEM}} '' ''
LOOP '' ''
{{CodeEnd}}
<center>{{text|Note: If you have a file named ''t3mpdata.tmp'' change the file name!|red}}</center>
 
 
{{PageSeeAlso}}
* [[SYSTEM]]
* [[END]]
* [[EXIT]]
 
 
{{PageNavigation}}

Latest revision as of 20:09, 5 September 2017

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.


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

Note: If you have a file named t3mpdata.tmp change the file name!


See also



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