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https://github.com/QB64-Phoenix-Edition/QB64pe.git
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6e01fc8dce
Added new _STRCMP and _STRICMP commands for quick string comparisons. Cleaned up QB64 to finish removing the QUI (quick user insert) code and folders. Altered UCASE and LCASE routines to be faster in some situations for us.
65 lines
2.9 KiB
Plaintext
65 lines
2.9 KiB
Plaintext
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}} |