Ways to trap function key

[eoredson]

This is not a bug report but I was about to declare an error.

This code contains 2 ways to trap the F1 key:

The difference is between soft key and scan key when key is set
  (has nothing to do with Key On or Key Off)..

Code: (Select All)

' Ways to trap function keys.
f$ = "EDIT"
KEY 1, f$ ' activate soft key.
Print "Press F1:"
Do
   x$ = InKey$
   If Len(x$) Then
      q$ = q$ + x$
   Else
      If Len(q$) Then
         Exit Do
      End If
   End If
Loop
If q$ = f$ Then
   Print "F1 pressed. (equals:"; q$; ")"
End If
KEY 1, "" ' decativate soft key.
Print "Press F1:"
Do
   x$ = InKey$
   If x$ = Chr$(0) + Chr$(59) Then
      Print "F1 pressed. (equals:"; Asc(Right$(x$, 1)); ")"
      Exit Do
   End If
Loop
End

[PhilOfPerth]

Maybe I'm missing the point here, but I find it easiest to use the _keyhit funcion, which returns the value 15104 for example, for F1

[SMcNeill]

No worries Phil; I missed whatever point there was as well and thought the same as you.  _KeyHit is your friend!

[bplus]

Don't think I ever used the Key method in Eric's first example. So it was news to me no matter long it's been around. Thanks Eric!

So that makes 4 ways to trap a key:
1. Inkey$
2. KeyHit
3. Keydown
4. Key

SmallBASIC had a way to associate a Key to a subroutine so that routine would execute when the Key was pressed, maybe ON KEY for us?

Just looked it up: Yes! On Key(1) would trap the F1 key and send you to a GoSub or Sub you setup on same command. Numbers 1-10 dedicated to Function keys then 11-14? the arrow keys, this old stuff probably came with QB4.5?

[TerryRitchie]

Don't think I ever used the Key method in Eric's first example. So it was news to me no matter long it's been around. Thanks Eric!

So that makes 4 ways to trap a key:
1. Inkey$
2. KeyHit
3. Keydown
4. Key

SmallBASIC had a way to associate a Key to a subroutine so that routine would  execute when the Key was pressed, maybe ON KEY for us?

Just looked it up: Yes! On Key(1) would trap the F1 key and send you to a GoSub or Sub you setup on same command. Numbers 1-10 dedicated to Function keys then 11-14? the arrow keys, this old stuff probably came with QB4.5?

This goes all the way back to GWBasic. When you start GWBasic you'll see a row of text at the bottom of the screen. Each word equates to an F key. This can be turned on and off using KEY ON/OFF. You as the programmer could also set these to whatever you liked as you have discovered.

That's why in many GWBasic programs the first line usually read:

KEY OFF: CLS

Here's a site with some info:

http://www.antonis.de/qbebooks/gwbasman/key.html

[bplus]

cool, thanks terry (my left shift key is worn out0 damn! Probably got some food stuck under it ;-))

I must of known this when I was using gw back in the late 80's early 90's. Must be the siren call of _KeyHit that made me forget

[SMcNeill]

Don't forget _DEVICES and INP, and PEEK/POKE methods, as well as various DECLARE LIBRARY code and $INCLUDE libraries...   

Wait...   Why is it any harder to read function keys than it is anything else, anyway?  It doesn't seem too limited to me.