' Follow steps 1a or 1b and then 2 to use this custom control in a XAML file.
'
' Step 1a) Using this custom control in a XAML file that exists in the current project.
' Add this XmlNamespace attribute to the root element of the markup file where it is 
' to be used:
'
'     xmlns:MyNamespace="clr-namespace:EgwWPFBaseLib"
'
'
' Step 1b) Using this custom control in a XAML file that exists in a different project.
' Add this XmlNamespace attribute to the root element of the markup file where it is 
' to be used:
'
'     xmlns:MyNamespace="clr-namespace:EgwWPFBaseLib;assembly=EgwWPFBaseLib"
'
' You will also need to add a project reference from the project where the XAML file lives
' to this project and Rebuild to avoid compilation errors:
'
'     Right click on the target project in the Solution Explorer and
'     "Add Reference"->"Projects"->[Browse to and select this project]
'
'
' Step 2)
' Go ahead and use your control in the XAML file. Note that Intellisense in the
' XML editor does not currently work on custom controls and its child elements.
'
'     <MyNamespace:EgwDropdown/>
'

Imports System.Windows.Controls.Primitives


Public Class EgwDropdownButton
   Inherits EgwToggleButton

   Public Enum PopupPlacementType
      BottomLeft
      BottomCenter
      BottomRight
      TopLeft
      TopCenter
      TopRight
      LeftTop
      LeftCenter
      LeftBottom
      RightTop
      RightCenter
      RightBottom
   End Enum

   Public Property DropDownContent As Object
      Get
         Return GetValue(DropDownContentProperty)
      End Get
      Set(value As Object)
         SetValue(DropDownContentProperty, value)
      End Set
   End Property

   Public Shared ReadOnly DropDownContentProperty As DependencyProperty =
        DependencyProperty.Register("DropDownContent",
                                    GetType(Object),
                                    GetType(EgwDropdownButton),
                                    New PropertyMetadata(Nothing))

   ' --- Placement del popup ---
   Public Property PopupPlacement As PopupPlacementType
      Get
         Return CType(GetValue(PopupPlacementProperty), PopupPlacementType)
      End Get
      Set(value As PopupPlacementType)
         SetValue(PopupPlacementProperty, value)
      End Set
   End Property

   Public Shared ReadOnly PopupPlacementProperty As DependencyProperty =
    DependencyProperty.Register("PopupPlacement",
                                GetType(PopupPlacementType),
                                GetType(EgwDropdownButton),
                                New PropertyMetadata(PopupPlacementType.BottomLeft))

   Shared Sub New()
      'This OverrideMetadata call tells the system that this element wants to provide a style that is different than its base class.
      'This style is defined in themes\generic.xaml
      DefaultStyleKeyProperty.OverrideMetadata(GetType(EgwDropdownButton), New FrameworkPropertyMetadata(GetType(EgwDropdownButton)))
   End Sub

   Public Overrides Sub OnApplyTemplate()
      MyBase.OnApplyTemplate()

      Dim popup = TryCast(GetTemplateChild("PART_Popup"), Popup)
      Dim root = TryCast(Me, FrameworkElement)

      If popup Is Nothing OrElse root Is Nothing Then Return

      ' PlacementTarget deve essere il controllo, non la freccia
      popup.PlacementTarget = root

      AddHandler popup.Opened,
    Sub()

       Dim child = popup.Child
       child.Measure(New Size(Double.PositiveInfinity, Double.PositiveInfinity))

       Dim popupWidth = child.DesiredSize.Width
       Dim popupHeight = child.DesiredSize.Height

       Dim rootWidth = root.ActualWidth
       Dim rootHeight = root.ActualHeight

       popup.HorizontalOffset = 0
       popup.VerticalOffset = 0

       Select Case PopupPlacement

            ' --- BOTTOM ---
          Case PopupPlacementType.BottomLeft
             popup.Placement = PlacementMode.Bottom

          Case PopupPlacementType.BottomCenter
             popup.Placement = PlacementMode.Bottom
             popup.HorizontalOffset = (rootWidth - popupWidth) / 2

          Case PopupPlacementType.BottomRight
             popup.Placement = PlacementMode.Bottom
             popup.HorizontalOffset = rootWidth - popupWidth

            ' --- TOP ---
          Case PopupPlacementType.TopLeft
             popup.Placement = PlacementMode.Top

          Case PopupPlacementType.TopCenter
             popup.Placement = PlacementMode.Top
             popup.HorizontalOffset = (rootWidth - popupWidth) / 2

          Case PopupPlacementType.TopRight
             popup.Placement = PlacementMode.Top
             popup.HorizontalOffset = rootWidth - popupWidth

            ' --- LEFT ---
          Case PopupPlacementType.LeftTop
             popup.Placement = PlacementMode.Left

          Case PopupPlacementType.LeftCenter
             popup.Placement = PlacementMode.Left
             popup.VerticalOffset = (rootHeight - popupHeight) / 2

          Case PopupPlacementType.LeftBottom
             popup.Placement = PlacementMode.Left
             popup.VerticalOffset = rootHeight - popupHeight

            ' --- RIGHT ---
          Case PopupPlacementType.RightTop
             popup.Placement = PlacementMode.Right

          Case PopupPlacementType.RightCenter
             popup.Placement = PlacementMode.Right
             popup.VerticalOffset = (rootHeight - popupHeight) / 2

          Case PopupPlacementType.RightBottom
             popup.Placement = PlacementMode.Right
             popup.VerticalOffset = rootHeight - popupHeight

       End Select
    End Sub
   End Sub

End Class