[BUG] The position draw on SKXamCanvas is not correct.

[xtuzy]

Description
I try use skiasharp draw something on uwp, but i find the position draw on SKXamCanvas is not correct.
when i draw a point on (50,50), i use mouse click the point ,get (40,40) by e.GetCurrentPoint(view).Position,
when i draw a point on (100,100),i use mouse click the point ,get (80,80) by e.GetCurrentPoint(view).Position,
when i draw a point on (400,400), i use mouse click the point ,get (320,320) by e.GetCurrentPoint(view).Position.
Then i use win2d.uwp do same thing, it's correct, draw point on (50,50),click it, i can get (50,50).
Then i use SKCanvasView do it on Android, it's correct,.

Code

if(something){
//something
}
//use win2d
else if (e.ClickedItem.Equals(Win2DDrawPositionTestListItem))
{
  //Container is a Grid
  Container.Children.Clear();
  var view = new CanvasControl();
  Container.Children.Add(view);
  
  Point clickPoint = new Point(0, 0);
  view.Draw += (senderTemp, eTemp) =>
  {
      var graphics = eTemp.DrawingSession;
      graphics.FillCircle(new System.Numerics.Vector2(50, 50), 2, SKColors.Red.ToColor());
      graphics.FillCircle(new System.Numerics.Vector2(100, 100), 2, SKColors.Red.ToColor());
      graphics.FillCircle(new System.Numerics.Vector2(400, 400), 2, SKColors.Red.ToColor());
      if (clickPoint.X != 0)
      {
          graphics.FillCircle(new System.Numerics.Vector2(400, 400), 1, SKColors.Yellow.ToColor());
      }
  };
  view.PointerPressed += (senderTemp, eTemp) =>
  {
       clickPoint = eTemp.GetCurrentPoint(view).Position;
       Debug.WriteLine(DateTime.Now + ": Click Position (" + clickPoint.X + "," + clickPoint.Y + ")");
   };
}
//use Skiasharp
else if (e.ClickedItem.Equals(SkiaDrawPositionTestListItem))
{
  Container.Children.Clear();
  var view = new SKXamlCanvas();
  Container.Children.Add(view);

  Point clickPoint = new Point(0, 0);
  var paint = new SKPaint() { Color = SKColors.Red, Style = SKPaintStyle.Fill };
  view.PaintSurface += (senderTemp, eTemp) =>
  {
      var graphics = eTemp.Surface.Canvas;
      graphics.DrawCircle(new SKPoint(50, 50), 5, paint);
      graphics.DrawCircle(new SKPoint(100, 100), 5, paint);
      graphics.DrawCircle(new SKPoint(400, 400), 5, paint);
      if (clickPoint.X != 0)
      {
          paint.Color = SKColors.Yellow;
          graphics.DrawCircle(clickPoint.ToSKPoint(), 3, paint);
      }
  };
  view.PointerPressed += (senderTemp, eTemp) =>
  {
      clickPoint = eTemp.GetCurrentPoint(view).Position;
      Debug.WriteLine(DateTime.Now + ": Click Position (" + clickPoint.X + "," + clickPoint.Y + ")");
  };
}

Xaml, this canvas will be replaced by win2d or skiasharp in C# code

<Grid x:Name="Container" Margin="12,12,0,0 " Grid.Row="2" >
    <Grid.RowDefinitions>
        <RowDefinition Height="*" />
    </Grid.RowDefinitions>
    <skia:SKXamlCanvas Name="canvas"  Background="Azure"/>
</Grid>

Expected Behavior

Actual Behavior

Basic Information

• Version with issue: 2.80.2
• Last known good version:
• IDE: Visual Studio
• Platform Target Frameworks:
  • Android:
  • iOS:
  • Linux:
  • macOS:
  • Tizen:
  • tvOS:
  • UWP: 18362
  • watchOS:
  • Windows Classic:
• Target Devices:

Detailed IDE/OS information (click to expand)

PASTE ANY DETAILED VERSION INFO HERE

Screenshots

Reproduction Link

[mattleibow]

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