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https://github.com/QB64-Phoenix-Edition/QB64pe.git
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65 lines
2.9 KiB
Plaintext
65 lines
2.9 KiB
Plaintext
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The {{KW|_EXIT (function)|_EXIT}} function prevents a program user exit and indicates if a user has clicked the close X window button or CTRL + BREAK.
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{{PageSyntax}}
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:{{Parameter|quit%}} = _EXIT
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{{PageDescription}}
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* Once the _EXIT function is used, the program user can no longer manually exit the program until it ends.
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* _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) box 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 a 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! The user may NOT appreciate that!
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''Example 1:'' Using an ON TIMER check to read the _EXIT request return values.
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{{CodeStart}} '' ''
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q = {{Cl|_EXIT (function)|_EXIT}} 'function read prevents any program exit at start of program
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{{Cl|ON TIMER (n)|ON TIMER}}(5) {{Cl|GOSUB}} quit
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{{Cl|TIMER}} ON
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{{Cl|PRINT}} " The Timer will check for exit request every 5 seconds."
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{{Cl|PRINT}} "Click the X box and/or Ctrl - Break to see the {{Cl|_EXIT (function)|_EXIT}} return!"
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{{Cl|PRINT}} " Any Key Quits"
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{{Cl|PRINT}}
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{{Cl|DO}}: {{Cl|_LIMIT}} 30
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' ' simulated program loop
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{{Cl|LOOP}} {{Cl|UNTIL}} {{Cl|INKEY$}} <> ""
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{{Cl|END}}
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quit:
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q = {{Cl|_EXIT (function)|_EXIT}}
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{{Cl|IF}} q {{Cl|THEN}} {{Cl|PRINT}} q;
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{{Cl|SELECT CASE}} q
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{{Cl|CASE}} 1: {{Cl|PRINT}} "= X button was clicked"
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{{Cl|CASE}} 2: {{Cl|PRINT}} "= Ctrl + Break keypress"
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{{Cl|CASE}} 3: {{Cl|PRINT}} "= Both X and Ctrl + Break!"
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{{Cl|END SELECT}}
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{{Cl|RETURN}} '' ''
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{{CodeEnd}}
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''Example 2:'' Removing temporary files before closing a program upon a user's exit request.
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{{CodeStart}} '' ''
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x = {{Cl|_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 {{Cl|_EXIT}} THEN {{Cl|CLOSE}}: {{Cl|KILL}} "t3mpdata.tmp": {{Cl|_DELAY}} 1: {{Cl|SYSTEM}} '' ''
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LOOP '' ''
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{{CodeEnd}}
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<center>{{text|Note: If you have a file named ''t3mpdata.tmp'' change the file name!|red}}</center>
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{{PageSeeAlso}}
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* [[SYSTEM]] {{text|(ends a program without notice and closes the window in QB64 or a Qbasic program run from the command line.)}}
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* [[END]] {{text|(ends a program displaying "Press any key to continue...".)}}
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* [[EXIT]] {{text|(ends a loop, SUB or FUNCTION)}}
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{{PageNavigation}}
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