Stopping customers from using Alt-Tab and the Windows-Key in my application. | Tech Off

intrepid

I have a WPF application that I want to remain on the screen on the notebooks in my shop, and I don't want customers to exit out of it. I don't mind if they press Alt-F4 (as exiting the application locks the computer) but I don't want any other keys to do anything at all.

I know this can be done, but not how it can be done in WPF/C#. Can someone provide samle code? Or does someone have a better solution?

Thanks, Intrepid.

W3bbo
The Master of Baiters

It's possible, just set up a keyboard hook and don't pass on the messages for certain keys.

footballism
Another Paradigm Shift!

I don't think you can do it in application code, since the alt-tab keystroke are system command which are processed by operating system before it gets dispatched and processed by your application's window procedure.

Sheva

sushovande
Smiley Face Sharp

I am pretty sure that the DirectX API reference has an article on how to do it. I will chip in with an edit later telling the exact URL.

Massif
aim stupidly high, expect to fail often.

Can't you just set the PCs so that your WPF app is the shell instead of explorer? Then there's nowhere for them to go if they manage to get out of your program.

I know it can be done in XP, and although I imagine the settings are the same for vista I can't remember them anyway.

CannotResolveSymbol
{insert caption here}

Massif wrote:
Can't you just set the PCs so that your WPF app is the shell instead of explorer? Then there's nowhere for them to go if they manage to get out of your program.

I know it can be done in XP, and although I imagine the settings are the same for vista I can't remember them anyway.

Yeah, that would probably be the way to go. You'll also want to restrict the Windows Security dialog (the one that pops up when you press control-alt-delete) using group policy so that Shut Down and Task Manager are disabled-- otherwise, anyone can turn off the computer or run arbitrary programs regardless of shell.

To change the shell for the current user (make sure you have another user set up on the machine, otherwise, with task manager disabled, you'll have to format and reinstall to get back to normal), go to HKEY_CURRENT_USER\Software\Microsoft\Windows NT\CurrentVersion\Winlogon, add a new string value called shell, and set its value to the path of the new shell.

Just make sure you have a way back out of this...

footballism
Another Paradigm Shift!

When I first read this post, I think Massif's answer should be the way to go if the original poster really wanna enable this kinda scenario, but from the deloyment perspective, this is something impossible. Yes, you can do it if the end-user's machine is at your disposal, but not otherwise.

Sheva

saporis
dreamt it, coded it, broke it.

My suggest, albeit bruteforce, would be to have a timer that is triggered every 1 second. If the program lost focus, have it bring it back. Anyone alt-tabbing will be annoyed.

Another method, would be a timer every 10 ms that checks for the alt modifier key ( if ( System.Windows.Forms.Control.ModifierKeys == System.Windows.Forms.Keys.Alt) ), and if so, pulls back the form to the front. Again, annoyance to the alt-tab.

Both of these ways will only cause the program to be brought almost immediately back. However, I'm sure the user will be quick to alt-F4...

asharism
erm...

saporis wrote:
My suggest, albeit bruteforce, would be to have a timer that is triggered every 1 second. If the program lost focus, have it bring it back. Anyone alt-tabbing will be annoyed.

Another method, would be a timer every 10 ms that checks for the alt modifier key ( if ( System.Windows.Forms.Control.ModifierKeys == System.Windows.Forms.Keys.Alt) ), and if so, pulls back the form to the front. Again, annoyance to the alt-tab.

Both of these ways will only cause the program to be brought almost immediately back. However, I'm sure the user will be quick to alt-F4...

Alt+F4 should be fine as you can handle that in your application...

asharism
erm...

EDIT: Posted the message twice accidentally...

saporis
dreamt it, coded it, broke it.

Oh, I know that...but, from what I am reading, this app will be running on the "customers" end. Thus, we need to finish our task infront, BUT, shouldn't lock down the "customers" computer...so we support a "failsafe"?

...is this correct?