DrawTreeNodeEventArgs.Graphics Property
Definition
Important
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public:
property System::Drawing::Graphics ^ Graphics { System::Drawing::Graphics ^ get(); };public System.Drawing.Graphics Graphics { get; }member this.Graphics : System.Drawing.GraphicsPublic ReadOnly Property Graphics As GraphicsProperty Value
A Graphics used to draw the TreeNode.
Examples
The following code example demonstrates how to customize a TreeView control using owner drawing. The TreeView control in the example displays optional node tags alongside the standard node labels. Node tags are specified using the TreeNode.Tag property. The TreeView control also uses custom colors, including a custom highlight color.
You can customize most of the TreeView colors by setting color properties, but the selection highlight color is not available as a property. Additionally, the default selection highlight rectangle extends only around a node label. Owner drawing must be used to draw the node tags and to draw a customized highlight rectangle large enough to include a node tag.
In the example, a handler for the TreeView.DrawNode event draws the node tags and the custom selection highlight manually. Unselected nodes do not need customization. For these, the DrawDefault property is set to true so that they will be drawn by the operating system.
For the complete example, see the DrawTreeNodeEventArgs overview reference topic.
// Draws a node.
private:
void myTreeView_DrawNode( Object^ sender, DrawTreeNodeEventArgs^ e )
{
// Draw the background and node text for a selected node.
if ( (e->State & TreeNodeStates::Selected) != (TreeNodeStates)0 )
{
// Draw the background of the selected node. The NodeBounds
// method makes the highlight rectangle large enough to
// include the text of a node tag, if one is present.
e->Graphics->FillRectangle( Brushes::Green, NodeBounds( e->Node ) );
// Retrieve the node font. If the node font has not been set,
// use the TreeView font.
System::Drawing::Font^ nodeFont = e->Node->NodeFont;
if ( nodeFont == nullptr )
nodeFont = (dynamic_cast<TreeView^>(sender))->Font;
// Draw the node text.
e->Graphics->DrawString( e->Node->Text, nodeFont, Brushes::White, Rectangle::Inflate( e->Bounds, 2, 0 ) );
}
// Use the default background and node text.
else
{
e->DrawDefault = true;
}
// If a node tag is present, draw its string representation
// to the right of the label text.
if ( e->Node->Tag != nullptr )
{
e->Graphics->DrawString( e->Node->Tag->ToString(), tagFont, Brushes::Yellow, (float)e->Bounds.Right + 2, (float)e->Bounds.Top );
}
// If the node has focus, draw the focus rectangle large, making
// it large enough to include the text of the node tag, if present.
if ( (e->State & TreeNodeStates::Focused) != (TreeNodeStates)0 )
{
Pen^ focusPen = gcnew Pen( Color::Black );
try
{
focusPen->DashStyle = System::Drawing::Drawing2D::DashStyle::Dot;
Rectangle focusBounds = NodeBounds( e->Node );
focusBounds.Size = System::Drawing::Size( focusBounds.Width - 1, focusBounds.Height - 1 );
e->Graphics->DrawRectangle( focusPen, focusBounds );
}
finally
{
if ( focusPen )
delete safe_cast<IDisposable^>(focusPen);
}
}
}
// Draws a node.
private void myTreeView_DrawNode(
object sender, DrawTreeNodeEventArgs e)
{
// Draw the background and node text for a selected node.
if ((e.State & TreeNodeStates.Selected) != 0)
{
// Draw the background of the selected node. The NodeBounds
// method makes the highlight rectangle large enough to
// include the text of a node tag, if one is present.
e.Graphics.FillRectangle(Brushes.Green, NodeBounds(e.Node));
// Retrieve the node font. If the node font has not been set,
// use the TreeView font.
Font nodeFont = e.Node.NodeFont;
if (nodeFont == null) nodeFont = ((TreeView)sender).Font;
// Draw the node text.
e.Graphics.DrawString(e.Node.Text, nodeFont, Brushes.White,
Rectangle.Inflate(e.Bounds, 2, 0));
}
// Use the default background and node text.
else
{
e.DrawDefault = true;
}
// If a node tag is present, draw its string representation
// to the right of the label text.
if (e.Node.Tag != null)
{
e.Graphics.DrawString(e.Node.Tag.ToString(), tagFont,
Brushes.Yellow, e.Bounds.Right + 2, e.Bounds.Top);
}
// If the node has focus, draw the focus rectangle large, making
// it large enough to include the text of the node tag, if present.
if ((e.State & TreeNodeStates.Focused) != 0)
{
using (Pen focusPen = new Pen(Color.Black))
{
focusPen.DashStyle = System.Drawing.Drawing2D.DashStyle.Dot;
Rectangle focusBounds = NodeBounds(e.Node);
focusBounds.Size = new Size(focusBounds.Width - 1,
focusBounds.Height - 1);
e.Graphics.DrawRectangle(focusPen, focusBounds);
}
}
}
' Draws a node.
Private Sub myTreeView_DrawNode(ByVal sender As Object, _
ByVal e As DrawTreeNodeEventArgs) Handles myTreeView.DrawNode
' Draw the background and node text for a selected node.
If (e.State And TreeNodeStates.Selected) <> 0 Then
' Draw the background of the selected node. The NodeBounds
' method makes the highlight rectangle large enough to
' include the text of a node tag, if one is present.
e.Graphics.FillRectangle(Brushes.Green, NodeBounds(e.Node))
' Retrieve the node font. If the node font has not been set,
' use the TreeView font.
Dim nodeFont As Font = e.Node.NodeFont
If nodeFont Is Nothing Then
nodeFont = CType(sender, TreeView).Font
End If
' Draw the node text.
e.Graphics.DrawString(e.Node.Text, nodeFont, Brushes.White, _
e.Bounds.Left - 2, e.Bounds.Top)
' Use the default background and node text.
Else
e.DrawDefault = True
End If
' If a node tag is present, draw its string representation
' to the right of the label text.
If (e.Node.Tag IsNot Nothing) Then
e.Graphics.DrawString(e.Node.Tag.ToString(), tagFont, _
Brushes.Yellow, e.Bounds.Right + 2, e.Bounds.Top)
End If
' If the node has focus, draw the focus rectangle large, making
' it large enough to include the text of the node tag, if present.
If (e.State And TreeNodeStates.Focused) <> 0 Then
Dim focusPen As New Pen(Color.Black)
Try
focusPen.DashStyle = System.Drawing.Drawing2D.DashStyle.Dot
Dim focusBounds As Rectangle = NodeBounds(e.Node)
focusBounds.Size = New Size(focusBounds.Width - 1, _
focusBounds.Height - 1)
e.Graphics.DrawRectangle(focusPen, focusBounds)
Finally
focusPen.Dispose()
End Try
End If
End Sub
Remarks
The Graphics class provides properties and methods useful for drawing on the display device.
