I'm trying to work through the WPF Unleashed book by Adam Nathan, as I'm going I'm working through with VB.NET rather than the C# samples in the book*just to see how it translates.
I have reached chapter 11 and the section about Hit Testing with Multiple Visuals.
The code in the book draws a ghost with mouth, eyes, and body all of which rotate seperately when clicked. The c# sample works fine from the authors site but when i translate it to VB.NET it doesn't work, after a bit of debugging the GetVisualChild overridden method only ever gets called with a value of 0 passed in while when running the c# sample it gets called with a value for each item (0,1,2) in the collection.
The code below is, as far as I can see, the exact equivalent of the C# in the book but it only draws the ghost's body (or if I change the order of the items in the 'visuals' list it is always the first item) which makes sense if GetVisualChild only gets called with a val of 0.
Public Class WPFHostDrawing2
Inherits Window
Dim visuals As New List(Of Visual)
Sub New()
Title = "Hosting DrawingVisuals"
Width = 300
Height = 350
Dim bodyVisual As New DrawingVisual()
Dim eyesVisual As New DrawingVisual()
Dim mouthVisual As New DrawingVisual()
Using dc As DrawingContext = bodyVisual.RenderOpen()
'The body
dc.DrawGeometry(Brushes.Blue, Nothing, Geometry.Parse("M 240,250 " & _
"C 200,375 200,250 175,200 " & _
"C 100,400 100,250 100,200" & _
"C 0,350 0,250 30,130" & _
"C 75,0 100,0 150,0" & _
"C 200,0 250,0 250,150 Z"))
End Using
Using dc As DrawingContext = eyesVisual.RenderOpen()
'left eye
dc.DrawEllipse(Brushes.Black, New Pen(Brushes.White, 10), New Point(95, 95), 15, 15)
'right eye
dc.DrawEllipse(Brushes.Black, New Pen(Brushes.White, 10), New Point(170, 105), 15, 15)
End Using
Using dc As DrawingContext = mouthVisual.RenderOpen()
'the mouth
Dim p As New Pen(Brushes.Black, 10)
p.StartLineCap = PenLineCap.Round
p.EndLineCap = PenLineCap.Round
dc.DrawLine(p, New Point(75, 160), New Point(175, 150))
End Using
visuals.Add(bodyVisual)
visuals.Add(eyesVisual)
visuals.Add(mouthVisual)
For Each v In visuals
AddVisualChild(v)
AddLogicalChild(v)
Next
End Sub
' The two necessary overrides, implemented for the single Visual:
Protected Shadows ReadOnly Property VisualChildrenCount() As Integer
Get
Return visuals.Count
End Get
End Property
Protected Overrides Function GetVisualChild(ByVal index As Integer) As Visual
If index < 0 OrElse index >= visuals.Count Then
Throw New ArgumentOutOfRangeException("index")
End If
Return visuals(index)
End Function
Private Sub WPFHostDrawing_MouseLeftButtonDown(ByVal sender As Object, ByVal e As System.Windows.Input.MouseButtonEventArgs) Handles Me.MouseLeftButtonDown
MyBase.OnMouseLeftButtonDown(e)
'Reteive the mouse pointer location relative to the Window
Dim location As Point = e.GetPosition(Me)
'Perform visual hit testing for the entire Window
Dim result As HitTestResult = VisualTreeHelper.HitTest(Me, location)
'If we hit any DrawingVisual, rotate it
If result.VisualHit.GetType() Is GetType(DrawingVisual) Then
Dim dv As DrawingVisual = result.VisualHit
If dv.Transform Is Nothing Then
dv.Transform = New RotateTransform()
End If
CType(dv.Transform, RotateTransform).Angle = CType(dv.Transform, RotateTransform).Angle + 1
End If
End Sub
End Class
Can anyone see an error, or just tell me they get the same and it must be a bug, it is driving my slightly crazy. Thanks.
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