line annotation not moving smoothly on windows phone using touch events..

[objorke]

From oxyplot: oxyplot/oxyplot#964

IF BUG, INCLUDE THIS PART:

Steps to reproduce

1. Add line annotation.

var la = new OxyPlot.Annotations.LineAnnotation { Type = OxyPlot.Annotations.LineAnnotationType.Vertical, X = DateTimeAxis.ToDouble(DictVarData.ElementAt(0).Name), Tag = model.Annotations.Count + 1 };

la.TouchStarted += (s, f) =>
            {
                la.StrokeThickness *= 1;
                model.InvalidatePlot(false);
                f.Handled = true;

            };
la.TouchDelta += (s, f) =>
            {
                la.X = la.InverseTransform(f.Position).X;
model.InvalidatePlot(false);
                f.Handled = true;
};
            la.TouchCompleted += (s, f) =>
            {
                la.StrokeThickness /= 1;
                model.InvalidatePlot(false);
                f.Handled = true;
            };

1. on touch delta line annotation x in changed as per position of touch.

Platform: Windows phone 8.1
.NET version: visual studio 2013

Expected behaviour

line not moving immediately and smoothly on chart. as it moving on mouse events. line annotation should move immediately as like mouse events in example browser.

Actual behaviour

line moving slow and screen not refreshed immediately.

@objorke @tibel @TheAlmightyBob