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Why arrowKey is not very useful
Posted: Tue Jul 14, 2020 8:51 pm
by richmond62
I have a set of online pupils/students just now who are trying to make simple games where the 'hero'
is controlled by the arrow keys on the computer keyboard a bit like this;
Code: Select all
on arrowKey AK
put item 1 of the loc of grc "ANT" into LR
put item 2 of the loc of grc "ANT" into UD
switch AK
case "up"
set the backgroundpattern of grc "ANT" to the ID of img "A1.png"
move grc "ANT" to LR,(UD-12)
break
---and so on and so forth
end switch
end arrowKey
BUT . . . the main problem is that if an end-user keeps pressing an arrow key the key keeps sending
keyDown signals
which is not desirable.
This has been an ongoing problem for some years.
If we change our control keys to, let us say the W, A, S & Z keys we can overcome that problem by using
keyUp rather than
keyDown.
But
arrowKey is a sort of kinky
keyDown confined to the arrow keys, there is not the possibility of either
(pseudoCode)
arrowKeyDown or
arrowKeyUp
I have been chewing over this one for a long, long time (well, about 5 years on and off) and, reluctantly reached
the conclusion that using
arrowKeywhen one wants to use the arrow keys is not very useful at all.
And doing this sort of thing when I want to use the arrow keys:
Code: Select all
on rawKeyUp XXX
put item 1 of the loc of grc "ANT" into LR
put item 2 of the loc of grc "ANT" into UD
switch XXX
case "65362" --- this is the rawKey code for the 'up' arrow key
set the backgroundpattern of grc "ANT" to the ID of img "A1.png"
move grc "ANT" to LR,(UD-12)
break
---and so on and so forth
end switch
end rawKeyUp
Re: Why arrowKey is not very useful
Posted: Tue Jul 14, 2020 9:11 pm
by richmond62
It's time for a
COMPARE & CONTRAST session:
-
Re: Why arrowKey is not very useful
Posted: Tue Jul 14, 2020 9:55 pm
by bogs
richmond62 wrote: ↑Tue Jul 14, 2020 8:51 pm
BUT . . . the main problem is that if an end-user keeps pressing an arrow key the key keeps sending keyDown signals
which is not desirable
I forget who it was, but someone (probably Craig, might even have been you!) had a solution for that.
I forgot now what it was, though, might have been to silently drop further key repeats that had piled up or some such. There were a variety of other ways to handle it listed in
this topic... including a very bad example by yours truly.
Re: Why arrowKey is not very useful
Posted: Wed Jul 15, 2020 2:37 am
by dunbarx
Richmond.
I don't understand. Trapping an arrowKey message will not also invoke a "keyDown" message.Add this to your script;
Code: Select all
on keydown tkey
put tkey
end keydown
When I press the arrowKey, the image goes up. When I press, say "k", I get a "k" in msg. Where are you getting yours?
Craig
Re: Why arrowKey is not very useful
Posted: Wed Jul 15, 2020 2:40 pm
by richmond62
When I press the arrowKey, the image goes up. When I press, say "k", I get a "k" in msg. Where are you getting yours?
The problem is not the
arrow keys Ding an Sich, it is the generic problem that when a user keeps a key depressed
it sends repeated signals.
If one wishes to avoid one's stack getting more than a single key signal one has to use
keyUp/rawKeyUp as in:
Code: Select all
on keyUp KUP
-- do something
end keyUp
The inherent problem about
arrowKey is that it is really a cloaked
keyDown, so to guarantee that
a user cannot send repeated signals (thus 'avoiding' later code) one must use
rawKeyUp with the
raw key values for the arrow keys rather than using
arrowKey at all.
Re: Why arrowKey is not very useful
Posted: Wed Jul 15, 2020 5:02 pm
by dunbarx
Ah.
So you meant "when the user keeps holding the arrowKey down" not "keeps pressing an arrow key".
OK.
The question is simply whether it is nobler in the mind to make kludges. This in the card script, on a card with a single button:
Code: Select all
on rawKeyup tkey
if tkey = 65362 then set the stopMoving of this cd to ""
end rawKeyup
on rawKeyDown tkey
if tkey = 65362 and the stopMoving of this cd ="" then set the top of btn 1 to the top of btn 1 -5
set the stopMoving of this cd to "true"
end rawKeyDown
Add the other values for the other arrowKeys.
Craig
Re: Why arrowKey is not very useful
Posted: Wed Jul 15, 2020 5:51 pm
by jacque
I'd probably use a script local instead of a custom property, but either way Craig's method works. I had some bad experiences with custom props accidentally stored in the wrong state on save, so I avoid them for transient storage.
Another method would be to track the milliseconds and only respond if the interval is long enough. That would function more like a throttle to slow down the ant's movement.
The arrowKey message isn't really a cloaked keyDown, it's just that you get all the keypress messages of which arrowKey is just one.
Re: Why arrowKey is not very useful
Posted: Wed Jul 15, 2020 6:32 pm
by dunbarx
Jacque.
I like that better as well.
Richard:
Code: Select all
local stopMoving
on rawKeyup tkey
if tkey = 65362 then put "" into stopMoving
end rawKeyup
on rawKeyDown tkey
if tkey = 65362 and stopMoving ="" then set the top of btn 1 to the top of btn 1 -5
put "true" into stopMoving
end rawKeyDown
Craig