How can I combine Touch and Mouse Event Handlers without producing duplicate behavior?

Question

I am working on a WPF application which is being used on a Touch Screen Tablet. I develop using VS2015 IDE and I use my Mouse to debug.

I must handle buttons' down and up events to execute certain tasks. I use PreviewMouse and PreviewTouch event handlers and I have a problem in every case I use:

• Case 1: Using PreviewMouseDown,PreviewMouseUp,PreviewTouchDown and PreviewTouchUp. For each button, I need to duplicate my code to include separate Touch and Mouse Event handlers but the exact same functionality. I do this for me to be able to use the Application (Mouse) and for the the user to use it (Touch). Problem: Touch Event Handlers executes Mouse Event Handlers; Causing the application to duplicate the behavior. Ex: A button that increments x by one, will increment by one if you "Click" it but increment by two if you "Touch" it.

• Case 2: Using Click, PreviewMouseUp and PreviewTouchUp. Problem: The PreviewTouchUp and PreviewMouseUp do not get called on Mouse Click.

• Case 3: Create a method for each button and call it from both Touch and Mouse events like How to get Touchscreen to use Mouse Events. Problem: Duplicate behavior (method gets called twice)

• Case 4: Remove all Touch events since PreviewMouseDown and PreviewMouseUp are being executed on any Touch. The behavior works but I need to Touch certain positions on the button in order for it to execute. (Transparency? I must touch exactly one position - like a mouse?)

• Case 5: Using MouseUp and MouseDown instead of Preview. Didn't work on Touch at all, touching any position on the button.

I want something similar to this Prevent a WPF application to interpret touch events as mouse events but only on the tablet. I still need to use my mouse in my environment. How can I fix that?

Button sample XAML:

<Button x:Name="locationScrollUpButton" Margin="0,5,5,0" Background="Transparent" Padding="0" Grid.Row="1" Grid.Column="1" PreviewMouseUp="locationScrollUpButton_PreviewMouseUp" PreviewMouseDown="locationScrollUpButton_PreviewMouseDown" BorderThickness="0" PreviewTouchDown="locationScrollUpButton_PreviewTouchDown" PreviewTouchUp="locationScrollUpButton_PreviewTouchUp" >
    <StackPanel>
        <TextBlock x:Name="locationUpButtonText" Text="Up" FontSize="13" Margin="0,2,0,4" HorizontalAlignment="Center" VerticalAlignment="Center"/>
        <Image x:Name="locationUpButtonImage" Source="/ProjectName;component/Resources/CaptureView/Location-Scroll-Up-White.png" Width="55" Height="60"/>
    </StackPanel>
</Button>

Answer 1

Check the StylusDevice property of the MouseEventArgs. If it is null, then the mouse event is not a promoted touch event. If it's not null, then the StylusDevice will be the touch device that initiated the touch that got promoted.