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How to: Implement a Custom ToolStripRenderer

You can customize the appearance of a ToolStrip control by implementing a class that derives from ToolStripRenderer. This gives you the flexibility to create an appearance that differs from the appearance provided the ToolStripProfessionalRenderer and ToolStripSystemRenderer classes.

The following code example demonstrates how to implement a custom ToolStripRenderer class. In this example, the GridStrip control implements a sliding-tile puzzle, which allows the user to move tiles in a table layout to form an image. A custom ToolStrip control arranges its ToolStripButton controls in a grid layout. The layout contains one empty cell, into which the user can slide an adjacent tile by using a drag-and-drop operation. Tiles that the user can move are highlighted.

The GridStripRenderer class customizes three aspects of the GridStrip control's appearance:

Imports System
Imports System.Collections.Generic
Imports System.Drawing
Imports System.Drawing.Drawing2D
Imports System.Drawing.Imaging
Imports System.Text
Imports System.Windows.Forms
Imports System.Windows.Forms.Layout


' The following class implements a sliding-tile puzzle. 
' The GridStrip control is a custom ToolStrip that arranges 
' its ToolStripButton controls in a grid layout. There is  
' one empty cell, into which the user can slide an adjacent 
' tile with a drag-and-drop operation. Tiles that are eligible  
' for moving are highlighted. 
Public Class GridStrip
    Inherits ToolStrip

   ' The button that is the drag source. 
   Private dragButton As ToolStripButton = Nothing 

   ' Settings for the ToolStrip control's TableLayoutPanel. 
   ' This provides access to the cell position of each 
   ' ToolStripButton. 
   Private tableSettings As TableLayoutSettings = Nothing 

   ' The empty cell. ToolStripButton controls that are 
   ' adjacent to this button can be moved to this button's 
   ' cell position. 
   Private emptyCellButton As ToolStripButton = Nothing 

   ' The dimensions of each tile. A tile is represented 
   ' by a ToolStripButton controls. 
   Private tileSize As New Size(128, 128)

   ' The number of rows in the GridStrip control. 
   Private rows As Integer = 5

   ' The number of columns in the GridStrip control. 
   Private columns As Integer = 5

   ' The one-time initialzation behavior is enforced 
   ' with this field. For more information, see the  
   ' OnPaint method. 
   Private firstTime As Boolean = False 

   ' This is a required by the Windows Forms designer. 
   Private components As System.ComponentModel.IContainer


   ' The default constructor.   
    Public Sub New()
        MyBase.New()

        Me.InitializeComponent()

        Me.InitializeTableLayoutSettings()
    End Sub 

   ' This property exposes the empty cell to the  
   ' GridStripRenderer class. 
   Friend ReadOnly Property EmptyCell() As ToolStripButton
      Get 
         Return Me.emptyCellButton
      End Get 
   End Property 


   ' This utility method initializes the TableLayoutPanel  
   ' which contains the ToolStripButton controls. 
    Private Sub InitializeTableLayoutSettings()

        ' Specify the numbers of rows and columns in the GridStrip control. 
        Me.tableSettings = CType(MyBase.LayoutSettings, TableLayoutSettings)
        Me.tableSettings.ColumnCount = Me.rows
        Me.tableSettings.RowCount = Me.columns

        ' Create a dummy bitmap with the dimensions of each tile. 
        ' The GridStrip control sizes itself based on these dimensions. 
        Dim b As New Bitmap(tileSize.Width, tileSize.Height)

        ' Populate the GridStrip control with ToolStripButton controls. 
        Dim i As Integer 
        For i = 0 To (Me.tableSettings.ColumnCount) - 1
            Dim j As Integer 
            For j = 0 To (Me.tableSettings.RowCount) - 1
                ' Create a new ToolStripButton control. 
                Dim btn As New ToolStripButton()
                btn.DisplayStyle = ToolStripItemDisplayStyle.Image
                btn.Image = b
                btn.ImageAlign = ContentAlignment.MiddleCenter
                btn.ImageScaling = ToolStripItemImageScaling.None
                btn.Margin = System.Windows.Forms.Padding.Empty
                btn.Padding = System.Windows.Forms.Padding.Empty

                ' Add the new ToolStripButton control to the GridStrip. 
                Me.Items.Add(btn)

                ' Set the cell position of the ToolStripButton control. 
                Dim cellPos As New TableLayoutPanelCellPosition(i, j)
                Me.tableSettings.SetCellPosition(btn, cellPos)

                ' If this is the ToolStripButton control at cell (0,0), 
                ' assign it as the empty cell button. 
                If i = 0 AndAlso j = 0 Then
                    btn.Text = "Empty Cell"
                    btn.Image = b
                    Me.emptyCellButton = btn
                End If 
            Next j
        Next i
    End Sub 


   ' This method defines the Paint event behavior. 
   ' The GridStripRenderer requires that the GridStrip 
   ' be fully layed out when it is renders, so this 
   ' initialization code cannot be placed in the 
   ' GridStrip constructor. By the time the Paint 
   ' event is raised, the control layout has been  
   ' completed, so the GridStripRenderer can paint 
   ' correctly. This one-time initialization is 
   ' implemented with the firstTime field. 
   Protected Overrides Sub OnPaint(e As PaintEventArgs)
      MyBase.OnPaint(e)

      If Not Me.firstTime Then 
         Me.Renderer = New GridStripRenderer()

         ' Comment this line to see the unscrambled image. 
         Me.ScrambleButtons()
         Me.firstTime = True 
      End If 
    End Sub 


   ' This utility method changes the ToolStripButton control  
   ' positions in the TableLayoutPanel. This scrambles the  
   ' buttons to initialize the puzzle. 
   Private Sub ScrambleButtons()
      Dim i As Integer = 0
      Dim lastElement As Integer = Me.Items.Count - 1

      While i <> lastElement AndAlso lastElement - i > 1
            Dim pos1 As TableLayoutPanelCellPosition = _
            Me.tableSettings.GetCellPosition(Me.Items(i))

            Dim pos2 As TableLayoutPanelCellPosition = _
            Me.tableSettings.GetCellPosition(Me.Items(lastElement))

            Me.tableSettings.SetCellPosition(Me.Items(i), pos2)
            i += 1

            Me.tableSettings.SetCellPosition(Me.Items(lastElement), pos1)
            lastElement -= 1
      End While 
    End Sub 


   ' This method defines the MouseDown event behavior.  
   ' If the user has clicked on a valid drag source,  
   ' the drag operation starts. 
   Protected Overrides Sub OnMouseDown(mea As MouseEventArgs)
      MyBase.OnMouseDown(mea)

        Dim btn As ToolStripButton = CType(Me.GetItemAt(mea.Location), ToolStripButton)

      If (btn IsNot Nothing) Then 
         If Me.IsValidDragSource(btn) Then 
            Me.dragButton = btn
         End If 
      End If 
    End Sub 


   ' This method defines the MouseMove event behavior.  
   Protected Overrides Sub OnMouseMove(mea As MouseEventArgs)
      MyBase.OnMouseMove(mea)

      ' Is a drag operation pending? 
      If (Me.dragButton IsNot Nothing) Then 
         ' A drag operation is pending. Call DoDragDrop to  
         ' determine the disposition of the operation. 
         Dim dropEffect As DragDropEffects = Me.DoDragDrop(New DataObject(Me.dragButton), DragDropEffects.Move)
      End If 
    End Sub 

   ' This method defines the DragOver event behavior.  
   Protected Overrides Sub OnDragOver(dea As DragEventArgs)
      MyBase.OnDragOver(dea)

      ' Get the ToolStripButton control  
      ' at the given mouse position. 
      Dim p As New Point(dea.X, dea.Y)
      Dim item As ToolStripButton = CType(Me.GetItemAt(Me.PointToClient(p)), ToolStripButton)


      ' If the ToolStripButton control is the empty cell, 
      ' indicate that the move operation is valid. 
        If item Is Me.emptyCellButton Then 
            ' Set the drag operation to indicate a valid move.
            dea.Effect = DragDropEffects.Move
        End If 
    End Sub 


   ' This method defines the DragDrop event behavior.  
   Protected Overrides Sub OnDragDrop(dea As DragEventArgs)
      MyBase.OnDragDrop(dea)

      ' Did a valid move operation occur? 
      If dea.Effect = DragDropEffects.Move Then 
         ' The move operation is valid. Adjust the state 
         ' of the GridStrip control's TableLayoutPanel, 
         ' by swapping the positions of the source button 
         ' and the empty cell button. 
         ' Get the cell of the control to move. 
         Dim sourcePos As TableLayoutPanelCellPosition = tableSettings.GetCellPosition(Me.dragButton)

         ' Get the cell of the emptyCellButton. 
         Dim dropPos As TableLayoutPanelCellPosition = tableSettings.GetCellPosition(Me.emptyCellButton)

         ' Move the control to the empty cell.
         tableSettings.SetCellPosition(Me.dragButton, dropPos)

         ' Set the position of the empty cell to  
         ' that of the previously occupied cell.
         tableSettings.SetCellPosition(Me.emptyCellButton, sourcePos)

         ' Reset the drag operation. 
         Me.dragButton = Nothing 
      End If 
    End Sub 


   ' This method defines the DragLeave event behavior.  
   ' If the mouse leaves the client area of the GridStrip 
   ' control, the drag operation is canceled. 
   Protected Overrides Sub OnDragLeave(e As EventArgs)
      MyBase.OnDragLeave(e)

      ' Reset the drag operation. 
      Me.dragButton = Nothing 
    End Sub 


   ' This method defines the ueryContinueDrag event behavior.  
   ' If the mouse leaves the client area of the GridStrip 
   ' control, the drag operation is canceled. 
   Protected Overrides Sub OnQueryContinueDrag(qcdevent As QueryContinueDragEventArgs)
      MyBase.OnQueryContinueDrag(qcdevent)

      ' Get the current mouse position, in screen coordinates. 
      Dim mousePos As Point = Me.PointToClient(Control.MousePosition)

      ' If the mouse position is outside the GridStrip control's 
      ' client area, cancel the drag operation. Be sure to 
      ' transform the mouse's screen coordinates to client coordinates.  
      If Not Me.ClientRectangle.Contains(mousePos) Then
         qcdevent.Action = DragAction.Cancel
      End If 
    End Sub 


   ' This utility method determines if a button 
   ' is positioned relative to the empty cell  
   ' such that it can be dragged into the empty cell. 
   Overloads Private Function IsValidDragSource(b As ToolStripButton) As Boolean 
      Dim sourcePos As TableLayoutPanelCellPosition = tableSettings.GetCellPosition(b)

      Dim emptyPos As TableLayoutPanelCellPosition = tableSettings.GetCellPosition(Me.emptyCellButton)

        Return IsValidDragSource(sourcePos, emptyPos)

    End Function 


   ' This utility method determines if a cell position 
   ' is adjacent to the empty cell. 
    Friend Overloads Shared Function IsValidDragSource( _
    ByVal sourcePos As TableLayoutPanelCellPosition, _
    ByVal emptyPos As TableLayoutPanelCellPosition) As Boolean 
        Dim returnValue As Boolean = False 

        ' A cell is considered to be a valid drag source if it 
        ' is adjacent to the empty cell. Cells that are positioned 
        ' on a diagonal are not valid. 
        If sourcePos.Column = emptyPos.Column - 1 AndAlso sourcePos.Row = emptyPos.Row OrElse _
        (sourcePos.Column = emptyPos.Column + 1 AndAlso sourcePos.Row = emptyPos.Row) OrElse _
        (sourcePos.Column = emptyPos.Column AndAlso sourcePos.Row = emptyPos.Row - 1) OrElse _
        (sourcePos.Column = emptyPos.Column AndAlso sourcePos.Row = emptyPos.Row + 1) Then
            returnValue = True 
        End If 

        Return returnValue
    End Function 

   ' This class implements a custom ToolStripRenderer for the  
   ' GridStrip control. It customizes three aspects of the  
   ' GridStrip control's appearance: GridStrip border,  
   ' ToolStripButton border, and ToolStripButton image. 
   Friend Class GridStripRenderer
        Inherits ToolStripRenderer

      ' The style of the empty cell's text. 
      Private Shared style As New StringFormat()

      ' The thickness (width or height) of a  
      ' ToolStripButton control's border. 
      Private Shared borderThickness As Integer = 2

      ' The main bitmap that is the source for the  
      ' subimagesthat are assigned to individual  
      ' ToolStripButton controls. 
      Private bmp As Bitmap = Nothing 

      ' The brush that paints the background of  
      ' the GridStrip control. 
      Private backgroundBrush As Brush = Nothing 


      ' This is the static constructor. It initializes the 
      ' StringFormat for drawing the text in the empty cell. 
      Shared Sub New()
         style.Alignment = StringAlignment.Center
         style.LineAlignment = StringAlignment.Center
      End Sub  

      ' This method initializes the GridStripRenderer by 
      ' creating the image that is used as the source for 
      ' the individual button images. 
      Protected Overrides Sub Initialize(ts As ToolStrip)
         MyBase.Initialize(ts)

         Me.InitializeBitmap(ts)
        End Sub 

      ' This method initializes an individual ToolStripButton 
      ' control. It copies a subimage from the GridStripRenderer's 
      ' main image, according to the position and size of  
      ' the ToolStripButton. 
      Protected Overrides Sub InitializeItem(item As ToolStripItem)
         MyBase.InitializeItem(item)

            Dim gs As GridStrip = item.Owner

         ' The empty cell does not receive a subimage. 
            If ((TypeOf (item) Is ToolStripButton) And _
                 (item IsNot gs.EmptyCell)) Then 
                ' Copy the subimage from the appropriate  
                ' part of the main image. 
                Dim subImage As Bitmap = bmp.Clone(item.Bounds, PixelFormat.Undefined)

                ' Assign the subimage to the ToolStripButton 
                ' control's Image property.
                item.Image = subImage
            End If 
      End Sub  

      ' This utility method creates the main image that 
      ' is the source for the subimages of the individual  
      ' ToolStripButton controls. 
      Private Sub InitializeBitmap(toolStrip As ToolStrip)
         ' Create the main bitmap, into which the image is drawn. 
         Me.bmp = New Bitmap(toolStrip.Size.Width, toolStrip.Size.Height)

         ' Draw a fancy pattern. This could be any image or drawing. 
         Dim g As Graphics = Graphics.FromImage(bmp)
         Try 
            ' Draw smoothed lines.
            g.SmoothingMode = SmoothingMode.AntiAlias

            ' Draw the image. In this case, it is  
            ' a number of concentric ellipses.  
            Dim i As Integer 
            For i = 0 To toolStrip.Size.Width - 8 Step 8
               g.DrawEllipse(Pens.Blue, 0, 0, i, i)
            Next i
         Finally
            g.Dispose()
         End Try 
      End Sub  

      ' This method draws a border around the GridStrip control. 
      Protected Overrides Sub OnRenderToolStripBorder(e As ToolStripRenderEventArgs)
         MyBase.OnRenderToolStripBorder(e)

         ControlPaint.DrawFocusRectangle(e.Graphics, e.AffectedBounds, SystemColors.ControlDarkDark, SystemColors.ControlDarkDark)
      End Sub  

      ' This method renders the GridStrip control's background. 
      Protected Overrides Sub OnRenderToolStripBackground(e As ToolStripRenderEventArgs)
         MyBase.OnRenderToolStripBackground(e)

         ' This late initialization is a workaround. The gradient 
         ' depends on the bounds of the GridStrip control. The bounds  
         ' are dependent on the layout engine, which hasn't fully 
         ' performed layout by the time the Initialize method runs. 
         If Me.backgroundBrush Is Nothing Then 
            Me.backgroundBrush = New LinearGradientBrush(e.ToolStrip.ClientRectangle, SystemColors.ControlLightLight, SystemColors.ControlDark, 90, True)
         End If 

         ' Paint the GridStrip control's background.
         e.Graphics.FillRectangle(Me.backgroundBrush, e.AffectedBounds)
        End Sub 

      ' This method draws a border around the button's image. If the background 
      ' to be rendered belongs to the empty cell, a string is drawn. Otherwise, 
      ' a border is drawn at the edges of the button. 
      Protected Overrides Sub OnRenderButtonBackground(e As ToolStripItemRenderEventArgs)
         MyBase.OnRenderButtonBackground(e)

         ' Define some local variables for convenience. 
         Dim g As Graphics = e.Graphics
         Dim gs As GridStrip = e.ToolStrip 
         Dim gsb As ToolStripButton = e.Item 

         ' Calculate the rectangle around which the border is painted. 
         Dim imageRectangle As New Rectangle(borderThickness, borderThickness, e.Item.Width - 2 * borderThickness, e.Item.Height - 2 * borderThickness)

         ' If rendering the empty cell background, draw an  
         ' explanatory string, centered in the ToolStripButton. 
            If gsb Is gs.EmptyCell Then
                e.Graphics.DrawString("Drag to here", gsb.Font, SystemBrushes.ControlDarkDark, imageRectangle, style)
            Else 
                ' If the button can be a drag source, paint its border red. 
                ' otherwise, paint its border a dark color. 
                Dim b As Brush = IIf(gs.IsValidDragSource(gsb), Brushes.Red, SystemBrushes.ControlDarkDark)

                ' Draw the top segment of the border. 
                Dim borderSegment As New Rectangle(0, 0, e.Item.Width, imageRectangle.Top)
                g.FillRectangle(b, borderSegment)

                ' Draw the right segment.
                borderSegment = New Rectangle(imageRectangle.Right, 0, e.Item.Bounds.Right - imageRectangle.Right, imageRectangle.Bottom)
                g.FillRectangle(b, borderSegment)

                ' Draw the left segment.
                borderSegment = New Rectangle(0, 0, imageRectangle.Left, e.Item.Height)
                g.FillRectangle(b, borderSegment)

                ' Draw the bottom segment.
                borderSegment = New Rectangle(0, imageRectangle.Bottom, e.Item.Width, e.Item.Bounds.Bottom - imageRectangle.Bottom)
                g.FillRectangle(b, borderSegment)
            End If 
        End Sub 
    End Class

   #Region "Windows Forms Designer generated code" 


   Private Sub InitializeComponent()
      Me.components = New System.ComponentModel.Container()
      Me.SuspendLayout()
      '  
      ' GridStrip 
      '  
      Me.AllowDrop = True 
      Me.BackgroundImageLayout = System.Windows.Forms.ImageLayout.None
      Me.CanOverflow = False 
      Me.Dock = System.Windows.Forms.DockStyle.None
      Me.GripStyle = System.Windows.Forms.ToolStripGripStyle.Hidden
      Me.LayoutStyle = System.Windows.Forms.ToolStripLayoutStyle.Table
      Me.ResumeLayout(False)
   End Sub 'InitializeComponent 

   #End Region

End Class

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