How can the 'fling/flick scrolling' be disabled in CefSharp.Wpf?

Question

Is there a way to disable the 'touch fling scrolling' behaviour in CefSharp.Wpf (or potentially via Cef, Chromium, etc)?

I appreciate it's an unusual request as touch fling scrolling is a great feature. But unfortunately, I need to integrate with a dodgy touch screen hw/driver which works nicely for drag.. but fails miserably when flick scrolling as it consistently 'over scrolls'. e.g. a gentle flick on the screen causes the page content to scroll multiple pages (instead of just a few lines).

Answer 1

There's no CefSharp/Cef/Chromium flag or public method available to cancel Chromium's fling behavior.

Fortunately though, Chromium does internally cancel the fling behavior under certain scenarios (refer Chromium's fling_controller.cc). One such scenario is a user touch down event.

So the trick is to simulate a touch down cancel event pair. Because CefSharp doesn't offer a 'post touch down' event for users to implement the logic (i.e. too much of an edge case), the easiest way is to implement the feature via a derived class.

Here's a complete example (with dependency property binding) in case it helps anyone else look for the same solution..

public class ChromiumWebBrowserEx : ChromiumWebBrowser
{
    public static readonly DependencyProperty IsFlingDisabledProperty = DependencyProperty.Register("IsFlingDisabled", typeof(bool), typeof(ChromiumWebBrowserEx));

    public bool IsFlingDisabled
    {
        get => (bool) GetValue(IsFlingDisabledProperty);
        set => SetValue(IsFlingDisabledProperty, value);
    }

    protected override void OnTouchUp(TouchEventArgs e)
    {
        base.OnTouchUp(e);

        if (IsFlingDisabled)
            CancelFling(e);
    }

    private void CancelFling(TouchEventArgs e)
    {
        // cancel the fling by creating a pseudo touch down followed by a cancellation
        var touchPoint = e.GetTouchPoint(this);
        if (touchPoint.Action == TouchAction.Up)
        {
            var touchEvent = new TouchEvent
                {
                    Id = e.TouchDevice.Id,
                    X = (float) touchPoint.Position.X,
                    Y = (float) touchPoint.Position.Y,
                    PointerType = PointerType.Touch,
                    Modifiers = WpfExtensions.GetModifierKeys(),
                    Type = TouchEventType.Pressed
                };

            GetBrowser().GetHost().SendTouchEvent(touchEvent);

            touchEvent.Type = TouchEventType.Cancelled;
            GetBrowser().GetHost().SendTouchEvent(touchEvent);
        }
    }
}