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Active Forums => QB64 Discussion => Topic started by: FilipeEstima on April 19, 2019, 04:11:36 pm

Title: Ideas on how to implement "ESC will force SYSTEM" at any time?
Post by: FilipeEstima on April 19, 2019, 04:11:36 pm
Is there a simple way to make a LONG program do its duties, while all the time checking if ESC is pressed - and if that's the case, immediately interrupt everything and do SYSTEM? That is, without creating a subroutine to check if INKEY$ equals to ESC and inserting GOSUBs to it, in *every single part* of the code?

I guess it would need a routine that works on interruption.
Title: Re: Ideas on how to implement "ESC will force SYSTEM" at any time?
Post by: Jack002 on April 19, 2019, 04:19:03 pm
Have you looked at the help area for the keyword INTERRUPT? I see there is a provision for it. I've never used it.

Are you a commodore 64 user? The C64 has one, the restore key. It does just what you're asking.
Title: Re: Ideas on how to implement "ESC will force SYSTEM" at any time?
Post by: FellippeHeitor on April 19, 2019, 04:56:10 pm
Use a TIMER:

Code: QB64: [Select]
  1. ON TIMER(.03) checkESC
  3.  
  5.     'this emulates your program doing its thing
  6.     _LIMIT 1
  8.  
  9. SUB checkESC

Also, at any time you can hit Alt+F4 (or just close the window).
Title: Re: Ideas on how to implement "ESC will force SYSTEM" at any time?
Post by: FellippeHeitor on April 19, 2019, 04:58:10 pm
Quote from: Jack002 on April 19, 2019, 04:19:03 pm
Have you looked at the help area for the keyword INTERRUPT? I see there is a provision for it. I've never used it.

Are you a commodore 64 user? The C64 has one, the restore key. It does just what you're asking.

Whatever INTERRUPT usage is accepted by QB64 is emulated and should be avoided in new code. Just makes no sense anymore since we're not directly talking to hardware these days.
Title: Re: Ideas on how to implement "ESC will force SYSTEM" at any time?
Post by: bplus on April 19, 2019, 05:06:55 pm
I worked up an example with ON TIMER
Code: QB64: [Select]
  1. t1 = _FREETIMER 'get a timer number from _FREETIMER ONLY!
  2. ON TIMER(t1, .05) TimerEvent
  3. TIMER(t1) ON
  4.  
  5. 'some old code to keep us occupied
  6.  
  7. 'fully factor.bas SmallBASIC 0.12.6 [B+=MGA] 2016-06-11
  8. m = 2
  10.     n = m
  11.     PRINT "Next n to factor is"; m
  12.     DO
  13.         fd = 0: test = 2
  14.         WHILE test <= n ^ .5
  15.             IF n MOD test = 0 THEN fd = test: EXIT WHILE
  16.             IF test = 2 THEN test = 3 ELSE test = test + 2
  17.         WEND
  18.         IF fd THEN n = n / fd: PRINT fd; " "; ELSE PRINT n
  19.     LOOP UNTIL fd = 0
  20.     m = m + 1
  21.     _LIMIT 10
  23.  
  24.  
  25. SUB TimerEvent
  26.     IF _KEYDOWN(27) THEN END
  28.  
  29.  
ESC does stop the program
Title: Re: Ideas on how to implement "ESC will force SYSTEM" at any time?
Post by: Pete on April 19, 2019, 05:18:12 pm
A good design would have your whole program in a DO/LOOP, so INKEY$ was being constantly polled between events. If that structure isn't easy to do, or impossible, the way to still achieve what you are asking for is to use ON KEY...

Example. Press Esc to terminate this program.

Code: QB64: [Select]
  1. KEY (15), CHR$(1) ' CHR$(1) is the scan code for the escape key. KEY 15 is one of the user defined ON KEYs available.
  2. KEY(15) ON
  3. ON KEY(15) GOSUB trap
  4. PRINT "Press Esc to quit."
  5. DO: _LIMIT 30: LOOP ' Your program code would replace this endless loop.
  6.  
  7. trap:
  9.  

Pete
Title: Re: Ideas on how to implement "ESC will force SYSTEM" at any time?
Post by: Raven_Singularity on April 19, 2019, 05:45:08 pm
CHR$(0) is a NUL byte.  CHR$(27) is Escape.  Hmm?
Title: Re: Ideas on how to implement "ESC will force SYSTEM" at any time?
Post by: Pete on April 19, 2019, 06:38:21 pm
Quote from: Raven_Singularity on April 19, 2019, 05:45:08 pm
CHR$(27) is Escape.  Hmm?

Not in %$%^$^ scan codes it isn't. It's CHR$(1).

Pete
Title: Re: Ideas on how to implement "ESC will force SYSTEM" at any time?
Post by: FilipeEstima on April 19, 2019, 07:16:19 pm
Thanks guys, I'll give these suggestions a shot.
Title: Re: Ideas on how to implement "ESC will force SYSTEM" at any time?
Post by: SMcNeill on April 19, 2019, 09:03:12 pm
One thing to note:  Some commands take *total* control of your program and *can not* be easily interrupted.   From the top of my head, if I’m remembering correctly, INPUT is one of them.  If you need a program to be response to various key/mouse states, at all times, be certain to never use INPUT in that program.  Use INKEY$, _KEYHIT, _DEVICE, INP, or some other method to get input from the program. 

INPUT itself takes total control and waits for that valid ENTER press before it releases control and resumes normal program operation.
Title: Re: Ideas on how to implement "ESC will force SYSTEM" at any time?
Post by: Pete on April 20, 2019, 11:34:08 am
Quote from: SMcNeill on April 19, 2019, 09:03:12 pm
One thing to note:  Some commands take *total* control of your program and *can not* be easily interrupted.   From the top of my head, if I’m remembering correctly, INPUT is one of them.  If you need a program to be response to various key/mouse states, at all times, be certain to never use INPUT in that program.  Use INKEY$, _KEYHIT, _DEVICE, INP, or some other method to get input from the program. 

INPUT itself takes total control and waits for that valid ENTER press before it releases control and resumes normal program operation.

Steve makes a good point, because not even ON KEY will get you out of an INPUT or LINE INPUT wait for user input statements. I've always considered INPUT and LINE INPUT to be beginner statements or just available if you are making a quick and easy utility and you don't want to bother to write just a couple more lines of code.

One thing I will give ON KEY is that even though it uses GOSUB, you can still get the key to respond while you are in a sub.

Code: QB64: [Select]
  1. KEY (15), CHR$(1) ' CHR$(1) is the scan code for the escape key. KEY 15 is one of the user defined ON KEYs available.
  2. KEY(15) ON
  3. ON KEY(15) GOSUB trap
  4. PRINT "Press Esc to quit."
  5. CALL waitforit
  6.  
  7. trap:
  9.  
  10. SUB waitforit
  11. DO: _LIMIT 30: LOOP ' Your program code would replace this endless loop.
  13.  

That was good engineering, but why they didn't make a way to get it to interrupt an input statement is beyond me.

Pete
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