UWP Canvas inside Scrollviewer handle pen input like mouse input

Question

I have a Canvas (not InkCanvas) inside a Scrollviewer. Both are not created in XAML but in code behind. I want to draw lines on my Canvas with Pen and Mouse input, everything works just fine but now I tested the whole thing with a pen as input device and the Scrollviewer seems to recognize it as touch input because the whole thing starts scrolling.

My question is: Is it possible to tell the Scrollviewer to ignore all inputs from a device type? Because it also seems like the Scrollviewer is 'eating' the events which should be fired from the Canvas.

Here my Scrollviewer init:

private void SetUpScrollViewer()
    {
        scroll = new ScrollViewer();

        scroll.VerticalScrollMode = ScrollMode.Auto;
        scroll.HorizontalScrollMode = ScrollMode.Auto;
        scroll.VerticalScrollBarVisibility = ScrollBarVisibility.Visible;
        scroll.HorizontalScrollBarVisibility = ScrollBarVisibility.Visible;
        scroll.ZoomMode = ZoomMode.Enabled;
        scroll.ManipulationMode = ManipulationModes.System;
        scroll.HorizontalAlignment = HorizontalAlignment.Left;
        scroll.VerticalAlignment = VerticalAlignment.Top;
        scroll.IsZoomInertiaEnabled = false;

        scroll.MinZoomFactor = 1;
        scroll.MaxZoomFactor = 5;
    }

Those are the events I use in my Canvas:

public void EnableDrawingOnCanvas(Canvas canvas)
    {
        //Adding the needed event handler.
        canvas.PointerPressed += Canvas_PointerPressed;
        canvas.PointerMoved += Canvas_PointerMoved;
        canvas.PointerReleased += Canvas_PointerReleased;
        canvas.PointerExited += Canvas_PointerExited;
    }

And those events all check if the input device is everything but touch like this

if (e.Pointer.PointerDeviceType != Windows.Devices.Input.PointerDeviceType.Touch){...}

But with those Events I can only check the input device for my Canvas and if I add a Event to the Scrollviewer it won't get passed to the Canvas afaik.

John Doe John Doe · Accepted Answer · 2017-11-05T18:09:44

You can bind a PointerPressed event to your ScrollViewer and check if the e.Pointer.PointerDeviceType equals PointerDeviceType.Pen. Then you can disable the VerticalScrollMode the HorizontalScrollMode and the ZoomMode like in the code below.

If you want to reactivate the ScrollViewer you can bind a PointerExited event to your ScrollViewer and reenable everything.

private void Scroll_PointerPressed(object sender, PointerRoutedEventArgs e)
{
    if (e.Pointer.PointerDeviceType == PointerDeviceType.Pen)
    {
        scroll.VerticalScrollMode = ScrollMode.Disabled;
        scroll.HorizontalScrollMode = ScrollMode.Disabled;
        scroll.ZoomMode = ZoomMode.Disabled;
    }
}

UWP Canvas inside Scrollviewer handle pen input like mouse input

1 Answers