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I have a problem with WPF application/presentation for Tablet PC with (multi-) touch screen. One "slide" of the presentation consists of Canvas on background and of a small UserControl. This UserControl is invisible at start, but whenever user touches the screen, it becomes visible and if user moves his finger, the control moves accordingly ("following" the finger, like a cursor). Then, when user stops touching the screen, the control becomes invisible again.

This is not very hard to do using the TouchDown, TouchUp and TouchMove event handlers and it works fine if user touches the screen with just one finger. However, when user holds one finger on position X (e.g. canvas coordinates [100,100]) and another finger on position Y (e.g. [500, 100]), the UserControl starts jumping between positions X and Y, which doesn't look very well...

Now I'd like the screen to react only to one touch at the time, which I can do in operating system (Windows 7) using Control Panel -> Pen and Touch -> Touch by unchecking item "Enable multi-touch gestures and inking".

This works fine, exactly as I want it to, unfortunately it's not very convenient, because sometimes I need to use the multi-touch and I can't change it every time I decide to use the application...

That's why I'd like to ask if there is any way how to disable the multi-touch programmaticaly, in the application (or just in WPF UserControl) where I need it. Thanks a lot in advance for any help.

Ondra C.
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3 Answers3

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Take a look at the TouchDevice.Id property. You can get this from the event arguments passed to the touch events and it will allow you to uniquely identify the touch events so that you don't confuse the first touch with subsequent parallel touches.

Dan Bryant
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You can convert the C++ code from the following question to C#: Programatically enable / disable multitouch finger input?

The CodeProject article, "Single App Instance in C#: Yet Another Way" has a C# implementation of the Win32 GlobalAddAtom() function and PInvoke.net has a reference page for SetProp().

Community
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Mark Cidade
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You can use a boolean eg. IsCurrentTouched, set it true if user touches and the control is shown, and set it back to false when the touch is released.

While IsCurrentTouched is true don't react to other touches. So you are able to use multitouch only when needed ;-)

Joey
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Tokk
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  • +1, the best way to resolve this is to accommodate the multitouch feature and deal with the resulting complexity (the need to filter out additional touches when only using the first touch as your input.) – Dan Bryant Apr 12 '11 at 16:06
  • Thanks for your answer, this would work if I just needed to hide/display the control... But I also have to update its position in TouchMove event handler... So I have to react to touches even when the control is shown... – Ondra C. Apr 12 '11 at 17:10