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Topic: Detecting a key release? (Read 360 times) |
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Monkfish
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Re: Detecting a key release?
« Reply #7 on: Feb 5th, 2018, 11:37am » |
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I'm not doing anything special, just detecting how many times the UP_ARROW key is pressed while the SHIFT key is being held down. Something like this...
Code:
print #main.gfx, "when characterInput [keypressed]"
'otherstuff
wait
'check if shift key or up_arrow pressed
[keypressed]
key$ = left$(Inkey$,2): a$ = right$(key$,1)
if len(key$) = 2 then
if a$ = chr$(_VK_SHIFT) then keycount = 0
if a$ = chr$(_VK_UP) then goto [up_pressed]
end if
'other stuff
wait
[up_pressed]
calldll #user32,"GetKeyState", _VK_SHIFT as long, r as long
if (r and 32768) then keycount = keycount + 1
'other stuff
wait
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Rod
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Re: Detecting a key release?
« Reply #8 on: Feb 5th, 2018, 4:23pm » |
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If you want to react to Shift Up Arrow then Inkey$ should contain chr$(4)+chr$(38). It will be chr$(0)+chr$(38) if the shift key is not down.
I would not bother about key releases. You can always check the keystate or check for the specific combination as above.
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Richard Russell
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Re: Detecting a key release?
« Reply #9 on: Feb 5th, 2018, 4:34pm » |
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on Feb 5th, 2018, 11:37am, Monkfish wrote:| I'm not doing anything special, just detecting how many times the UP_ARROW key is pressed while the SHIFT key is being held down. |
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Testing for Shift+UpArrow is surely just a case of comparing Inkey$ with chr$(4)+chr$(38):
Code: open "Test" for graphics as #main
print #main, "when characterInput [keypressed]"
'otherstuff
wait
'check if shift + up_arrow pressed
[keypressed]
if Inkey$ = chr$(4) + chr$(38) then
keycount = keycount + 1
print keycount
end if
wait
I don't see the need to use an API call to test the state of the Shift key when that information is conveyed in Inkey$ anyway. Am I missing something?
Richard.
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Monkfish
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Re: Detecting a key release?
« Reply #10 on: Feb 5th, 2018, 9:07pm » |
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That's why I rarely post any of my code... it's just an embarrassment 
Thanks guys 
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Rod
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Re: Detecting a key release?
« Reply #11 on: Feb 5th, 2018, 9:19pm » |
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Slight tweak to increase keycount if sequence of shift / up arrow else zero keycount.
After putting my ipad aside I see it also needed code to handle the stream of shift key presses from auto repeat.
Ahh defeated again! it is the final shift up message that makes my code work in LB but it fails to zero the counter in LBB till another key is pressed.
Code:open "Test" for graphics as #main
#main "when characterInput [keypressed]"
#main "setfocus"
'otherstuff
wait
'check if shift + up_arrow pressed
[keypressed]
if Inkey$ = chr$(4) + chr$(38) then
keycount = keycount + 1
else
if Inkey$ <> chr$(4)+chr$(16) then
keycount = 0
end if
end if
print keycount
wait
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| « Last Edit: Feb 6th, 2018, 07:38am by Rod » |
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Monkfish
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Re: Detecting a key release?
« Reply #12 on: Feb 6th, 2018, 07:56am » |
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Thanks Rob and Richard. I guess I was assuming that the shift+uparrow inkey$ code would only be generated the first time shift was pressed and that holding the shift key down and repeatedly pressing uparrow would subsequently only generate uparrow codes. Which is why I was using the dll call to determine whether the shift key was still down.
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| « Last Edit: Feb 6th, 2018, 07:56am by Monkfish » |
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Richard Russell
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Re: Detecting a key release?
« Reply #13 on: Feb 6th, 2018, 08:17am » |
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on Feb 6th, 2018, 07:56am, Monkfish wrote:| I was assuming that the shift+uparrow inkey$ code would only be generated the first time shift was pressed |
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I can't speculate on how it works in LB 4, but in LBB the first byte of Inkey$ (which contains the Shift, Ctrl and Alt status) is derived by calling exactly the same API that you were using! You might as well let LBB do the work.
Richard.
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SarmedNafi
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Re: Detecting a key release?
« Reply #14 on: Feb 6th, 2018, 08:48am » |
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Richard said,
>>> No it doesn't, Rod is right. Indeed I have looked at the code of LBB, and - as I confirmed - key release events (technically the WM_KEYUP message) are completely ignored.
I believe Richard, but it could be broken since many versions of LBB was released.
Anatoly,
We spent many nights offline, I will prepare the code.
Regards
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Rod
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Re: Detecting a key release?
« Reply #15 on: Feb 6th, 2018, 10:46am » |
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Quote:| I was assuming that the shift+uparrow inkey$ code would only be generated the first time shift was pressed and that holding the shift key down and repeatedly pressing uparrow would subsequently only generate uparrow codes. |
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No, it is a little more complex but fairly straightforward. If any control key is down Inkey$ will return two characters. The first tells you what control keys are down. If only one control key is down you simply get its code so chr$(4) for shift, chr$(8) for ctrl. If both are down you would get chr$(12). So you might need to AND out the specific key you are looking to check. The second character will contain the code of the control key itself IF, nothing else is pressed. If anything else is pressed then you get that keys code. Chr$(38) in the case of Up Arrow.
Over and above that Auto Repeat kicks in. So your handler will receive a stream of keypress events. Most will be chr$(4)+chr$(16) ie shift is down and interspersed some chr$(4)+chr$(38) telling you both shift and up arrow are down.
In LB there is a final keypress message telling us shift is up. This is not ported through in LBB. So big deal or not?
Well in fifteen years of playing with LB I have never seen anyone code for a keyup event. Most often it will be completely ignored.
How about a change of control strategy? How else could you zero or reset your counter?
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Richard Russell
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Re: Detecting a key release?
« Reply #16 on: Feb 6th, 2018, 11:49am » |
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on Feb 6th, 2018, 10:46am, Rod wrote:| Well in fifteen years of playing with LB I have never seen anyone code for a keyup event. |
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Hardly surprising, given that it's undocumented! Indeed, as the LB Help file always refers to 'key press' events there is no reason for anybody (including me!) to guess that 'key release' events are ever generated.
When designing LBB to be as compatible with LB 4 as I reasonably could, my sources of information were (1) the LB Help file and (2) existing programs that I gathered from wherever I could. Neither of those sources led me to suspect that there are any key release events.
Richard.
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SarmedNafi
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Re: Detecting a key release?
« Reply #17 on: Feb 6th, 2018, 1:24pm » |
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Anatoly,
Here is the demo,
Code:
REM Keypress Key Release Demo By Sarmed Nafi'
REM Keys and Shift + Key
REM Keys F2 F3 Up Down Left Right Shift + Left Shift + Right
REM Works with LBB better than LB
timer 1, [loop]
[loop]
scan
if (keyState(_VK_F2 )=1) AND (F2=0) then ' >> >> F2
F2=1
PRINT "F2 pressed" : PRINT
else
if (keyState(_VK_F2 )=0) AND (F2=1) then 'Reset
F2=0
PRINT "F2 released" : PRINT
else
if (keyState(_VK_F3 )=1) AND (F3=0) then ' >> >> F3
F3=1
PRINT "F3 pressed" : PRINT
else
if (keyState(_VK_F3 )=0) AND (F3=1) then 'Reset
F3=0
PRINT "F3 released" : PRINT
else
if (keyState(_VK_UP )=1) AND (up=0) AND (Fhndl=hDate) then ' >> >> UP
up=1
PRINT "Up Arrow pressed" : PRINT
else
if (keyState(_VK_UP )=0) AND (up=1) then 'Reset
up=0
PRINT "Up Arrow released" : PRINT
else
if (keyState(_VK_DOWN )=1) AND (dwn=0) AND (Fhndl=hDate) then ' >> >> Dwn
dwn=1
PRINT "Down Arrow pressed" : PRINT
else
if (keyState(_VK_DOWN )=0) AND (dwn=1) then 'Reset
dwn=0
PRINT "Down Arrow released" : PRINT
else
if (keyState(_VK_RIGHT )=1) AND (Rt=0) AND (keyState(_VK_SHIFT )=0) then ' >> >> Right
Rt=1
PRINT "Right Arrow pressed" : PRINT
else
if (keyState(_VK_RIGHT )=0) AND (Rt=1) AND (keyState(_VK_SHIFT )=0) then 'Reset
Rt=0
PRINT "Right Arrow released" : PRINT
else
if (keyState(_VK_RIGHT )=1) AND (shRt=0) AND (keyState(_VK_SHIFT )=1) then ' >> >> Shift + Right
shRt=1
PRINT "Shift + Right Arrow pressed" : PRINT
else
if (keyState(_VK_RIGHT )=0) AND (shRt=1) AND (keyState(_VK_SHIFT )=1) then 'Reset
shRt=0
PRINT "Shift + Right Arrow released" : PRINT
else
if (keyState(_VK_LEFT )=1) AND (lft=0) AND (keyState(_VK_SHIFT )=0) AND Grd=0 then ' >> >> Left
lft=1
PRINT "Left Arrow pressed" : PRINT
else
if (keyState(_VK_LEFT )=0) AND (lft=1) AND (keyState(_VK_SHIFT )=0) then 'Reset
lft=0
PRINT "Left Arrow released" : PRINT
else
if (keyState(_VK_LEFT )=1) AND (shlft=0) AND (keyState(_VK_SHIFT )=1) AND Grd=0 then ' >> >> Shift + Left
shlft=1
PRINT "Shift + Left Arrow pressed" : PRINT
else
if (keyState(_VK_LEFT )=0) AND (shlft=1) AND (keyState(_VK_SHIFT )=1) then 'Reset
shlft=0
PRINT "Shift + Left Arrow released" : PRINT
end if
end if
end if
end if
end if
end if
end if
end if
end if
end if
end if
end if
end if
end if
end if
end if
WAIT
'------
function keyState(keycode)
calldll #user32, "GetAsyncKeyState", keycode AS Ulong, state AS short
if state<0 then
keyState = 1
else
keyState = 0
end if
end function
'------
The code works under LBB better than LB.
Regards,
Sarmed.
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Richard Russell
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Re: Detecting a key release?
« Reply #18 on: Feb 6th, 2018, 2:58pm » |
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on Feb 6th, 2018, 1:24pm, SarmedNafi wrote:| The code works under LBB better than LB. |
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That code uses polling. This thread has been about the triggering (or not) of an event when a key is pressed or released.
Polling in a timer handler, as you do, and then calling the 'event' handler accordingly can be an acceptable workaround, but as Rod said it's not always a very satisfactory approach. For example it ties up the timer and, potentially, has a much greater latency than a true event.
Richard.
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SarmedNafi
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Re: Detecting a key release?
« Reply #19 on: Feb 6th, 2018, 9:38pm » |
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I remember that days I worked hard to find a way using INKEY$, unfortunately, INKEY$ is a simple command.
I think VB6 has the same mechanism inside its engine or similar to that I used to trap keyboard event.
Quote:but as Rod said it's not always a very satisfactory approach.
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Rod said that because he knows TIMER is broken under Liberty Basic.
I was made a very large search to discover how that big 3d games written under LB using TIMER command. The shock was they don't use the TIMER at all.
If anyone uses my code under LB he will put himself in trouble and be wasting his time. Then he will find there is no way but to use LBB.
When we were kids at sixties we advised each other "Don't ride a bicycle from Japan ride a bicycle from ENGLAND", It seems nothing change.
Sarmed
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| « Last Edit: Feb 6th, 2018, 10:11pm by SarmedNafi » |
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Monkfish
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Re: Detecting a key release?
« Reply #20 on: Feb 7th, 2018, 09:32am » |
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Thanks guys, and thanks Rob for clearing up exactly how Inkey$ works.
Btw, I haven't looked at LB for a while. I only use LBB. Thanks Richard for still being here for us 
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