Strange ALT+TAB bug

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Strange ALT+TAB bug

Postby danielc » 2009-4-13 @ 02:50

I searched for this to see if anyone else reported it, but it's one of those things that isn't easily explained.... dunno if it's just my hardware configuration or if others are having it....

What happens is, say i'm just at the command prompt in DOSBox, if I ALT+TAB (or simply switch to another window) in Windows, do some stuff, then switch back to DOSBox, a wierd thing happens 90% of the time... it's as if the TAB key is being held down.... as fast as the keyboard repeat/delay allows, the autocomplete filenames in the current folder rapidly change (and loop). As if you're holding TAB... even though you're not. You have to press TAB, or UP/DOWN arrow, or ESC... followed by ENTER or BACKSPACE to get rid of the autocomplete filename it was left on when you interrupted it....

....does that make sense? Has anybody else witnessed this? Only bug i've managed to come across lately. O.S. is Windows 7 Build 7057 64-bit (but it also happened in Vista SP1 32-bit from memory).
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Re: Strange ALT+TAB bug

Postby lightmaster » 2009-4-13 @ 03:52

xp here, what vga do you have? i've seen similar problems with ati cards.
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Re: Strange ALT+TAB bug

Postby danielc » 2009-4-13 @ 04:29

My hosts' graphics card....? It's a GeForce 9600GT. Yeah I am using the WDDM v1.1 Pre-release Forceware drivers, but since I started the thread I went and tested it in XP 32-bit too (which has 182.xx Forceware WHQL signed) - same thing happens.

I think it might be my keyboard or mouse. It's very easy for me to duplicate the problem, so I will try different mouse/keyboard and see if it still happens.

Oh... and its DOSBox 0.72, and my joystick is disabled :)
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Re: Strange ALT+TAB bug

Postby MiniMax » 2009-4-13 @ 12:04

You test Win7, Vista and XP on the same hardware, and had the same problem?
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Re: Strange ALT+TAB bug

Postby danielc » 2009-4-13 @ 13:03

MiniMax wrote:You test Win7, Vista and XP on the same hardware, and had the same problem?


Uhuh.... Win7 x64 with 'standard keyboard' driver coz of that wierd keymap issue (with the slashes and stuff), Vista 32-bit with default keyboard driver, and XP 32-bit with whatever it has....

....eh I always blame Windows/software before going to the bother of trying different hardware. Will do so as soon as I can and post back =)

EDIT: Definately the TAB 'autocomplete' key being "sticky". Never seen anything like this before.
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Re: Strange ALT+TAB bug

Postby MiniMax » 2009-4-13 @ 13:17

Every 14 months or so, I get my keyboard into some weird state where the CTRL-key is stuck software-wise. Something about me keeping the SHIFT-key down too long while thinking or something.

I reboot, then I google for an explanation, find it and swear to remember how to undo it next time (something about accessibility). And 14 months later, I have forgotten how to fix it :(
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Re: Strange ALT+TAB bug

Postby danielc » 2009-4-13 @ 13:26

Haha.. i believe you are referring to STICKY keys and the other things from Accessibility in Control Panel.... ;) I have that on my checklist of things to do whenever I install an OS... "Turn off all Accessibility shortcut keys".

Good call, but it's definately not that.... i've never had such a wierd input issue since discovering that crap, this is the first ever since... and it's isolated to DOSBox....

I have a feeling it might be something to do with autolock and the output method. As if... I alt-tab to dosbox, and because it locks/gains focus, the 'tab' from the ALT-TAB get's stuck in the input buffer somehow...

....there we go, i'll try turning off autolock and switching to opengl or something and see if it still does it. I wont be using DOSBox for a few days though I don't think [ah back to work after the long weekend] but we'll see. Well thanks for making me think of that! =D
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Re: Strange ALT+TAB bug

Postby wd » 2009-4-13 @ 13:59

Can't reproduce the problem, but with a bit of luck the next version fixes that.
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Re: Strange ALT+TAB bug

Postby danielc » 2009-4-18 @ 07:14

Yeah I tried a PS/2 keyboard, still happens.

I dunno. Doesn't really matter, it's a minor annoyance - just thought someone might have come across it before is all. Thanks guys :)
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Re: Strange ALT+TAB bug

Postby DMay » 2014-1-13 @ 17:20

I know this is an older post, but ...

I have the same problem. I use DosBox (0.74) primarily to run a text-based program (DOS version of the MultiEdit editor, been using it since college). Whether I am in that program, or just at the DOS prompt, if I alt-tab to another window, then alt-tab back to the DosBox win, it will (~90 % of the time) act as if I am holding down the <Tab> key until I hit any other key.

I have had this has occur in both Vista and Win 7, on 2 different HP laptops (old laptop both OS's, new laptop as only had Win 7).

Some pertinent items from the .conf file for a plain DOS window:

[sdl]
fullscreen=false
fulldouble=false
fullresolution=original
#windowresolution=original
windowresolution=960x600
#windowresolution=1280x800
output=surface
autolock=true
sensitivity=100
waitonerror=true
priority=higher,normal
#priority=normal,pause
mapperfile=mapper-0.74.map
usescancodes=true

[dosbox]
language=
#machine=svga_s3
machine=svga_s3
captures=vgaonly
memsize=16

[render]
frameskip=0
aspect=false
scaler=advinterp2x forced

[cpu]
core=auto
cputype=auto
#cycles=auto
cycles=max
#cycles=10000
cycleup=10
cycledown=20

[dos]
xms=true
ems=true
umb=true
keyboardlayout=auto

[autoexec]
mount c c:\
c:
cd \dan
path=z:\;c:\dan\bin\winpath;c:\dan\me
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Re: Strange ALT+TAB bug

Postby samcormack » 2017-12-01 @ 19:49

Don't know if this is still relevant to anybody, but hitting the Windows key instead of Alt+Tab should resolve it. :)
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