[Skia.WPF] Multi-Touch support

[lindexi]

What would you like to be added

Adding the multi-touch support to UNO.Skia.WPF.

Why is this needed

The original WPF has very good touch support. But that's what UNO.Skia.WPF is missing right now. See #4309

For which platform

Skia.WPF

Anything else we need to know?

WPF distinguishes WM_Pointer from Mouse and Stylus and Touch events.

[lindexi]

I'm delighted to be involved in the development of this feature, and I'm also quite familiar with the touch and ink modules of WPF.

[Youssef1313]

@lindexi I don't think this was implemented. So, re-opening it.

[lindexi]

Thank you @Youssef1313

[lindexi]

After reviewing the source code of UNO, I believe we can modify the original method of only obtaining events from the Mouse, to simultaneously obtaining events from both the Stylus and Mouse. Moreover, when the Mouse determines that the current event is from the Stylus or Touch, it will automatically ignore the subsequent processing logic. According to the touch behavior of WPF, the Touch event is triggered first, then promoted to the Stylus event, and finally promoted to the Mouse event. At the same time, Pen messages will trigger the Stylus event first, and then be promoted to the Mouse event. This means that for simple processing, using the Stylus event can handle both Touch and Pen situations. When using the Stylus event, multi-touch support will be automatically enabled. Also, by using the GetPropertyValue method and passing in StylusPointProperties.Width and StylusPointProperties.Height, we can obtain the possible size of the touch, which can be used to fill in the Microsoft.UI.Input.PointerPointProperties.ContactRect attribute. This will be beneficial for WPF applications on touch screens using the UNO framework.

    private void MainWindow_StylusDown(object sender, StylusDownEventArgs e)
    {
        var stylusPointCollection = e.GetStylusPoints(this);
        var firstStylusPoint = stylusPointCollection.First();

        if (firstStylusPoint.HasProperty(StylusPointProperties.Width))
        {
            var width = firstStylusPoint.GetPropertyValue(StylusPointProperties.Width);
        }

        if (firstStylusPoint.HasProperty(StylusPointProperties.Height))
        {
            var height = firstStylusPoint.GetPropertyValue(StylusPointProperties.Height);
        }
    }

[MartinZikmund]

I think the ability to distinguish input types is working since #15543 , but maybe the additional properties are missing?

[lindexi]

@MartinZikmund Sorry for delay. As you can see, the WpfCorePointerInputSource will only add the Mouse events and it do not add any Stylus and Touch event. That means it can not handle the multi-touch events.

[lindexi]

@MartinZikmund I create #16378 and could you review my code?

[MartinZikmund]

The changes are merged now!