VisualStyleRenderer.GetBackgroundRegion(IDeviceContext, Rectangle) Method

Definition

Namespace:

System.Windows.Forms.VisualStyles

Assembly:

System.Windows.Forms.dll

Source:

VisualStyleRenderer.cs

Returns the region for the background of the current visual style element.

public:
 System::Drawing::Region ^ GetBackgroundRegion(System::Drawing::IDeviceContext ^ dc, System::Drawing::Rectangle bounds);

public System.Drawing.Region? GetBackgroundRegion (System.Drawing.IDeviceContext dc, System.Drawing.Rectangle bounds);

member this.GetBackgroundRegion : System.Drawing.IDeviceContext * System.Drawing.Rectangle -> System.Drawing.Region

Public Function GetBackgroundRegion (dc As IDeviceContext, bounds As Rectangle) As Region

Parameters

dc

IDeviceContext

The IDeviceContext this operation will use.

bounds

Rectangle

A Rectangle that contains the entire background area of the current visual style element.

Returns

Region

The Region that contains the background of the current visual style element.

Exceptions

ArgumentNullException

dc is null.

Examples

The following code example demonstrates how to use the GetBackgroundRegion method in a custom control. This example uses GetBackgroundRegion to get the Region of the window title bar element returned by the VisualStyleElement.Window.Caption.Active property. This Region is used to set the Control.Region property of the control, so that the window title bar will appear with the rounded corners defined by the standard Windows XP visual style. This code example is part of a larger example provided for the VisualStyleRenderer class overview.

    // Calculate and set the clipping region for the control
    // so that the corners of the title bar are rounded.
private:
    void SetClipRegion()
    {
        if (!Application::RenderWithVisualStyles)
        {
            return;
        }

        Graphics^ g = this->CreateGraphics();
        // Get the current region for the window caption.
        if (SetRenderer(windowElements["windowCaption"]))
        {
            System::Drawing::Region^ clipRegion =
                renderer->GetBackgroundRegion(g,
                elementRectangles["windowCaption"]);

            // Get the client rectangle, but exclude the region
            // of the window caption.
            int height = (int)clipRegion->GetBounds(g).Height;
            System::Drawing::Rectangle nonCaptionRect = Rectangle(
                ClientRectangle.X, ClientRectangle.Y + height,
                ClientRectangle.Width, ClientRectangle.Height - height);

            // Add the rectangle to the caption region, and
            // make this region the form's clipping region.
            clipRegion->Union(nonCaptionRect);
            this->Region = clipRegion;
        }

    }

// Calculate and set the clipping region for the control  
// so that the corners of the title bar are rounded.
private void SetClipRegion()
{
    if (!Application.RenderWithVisualStyles)
    {
        return;
    }

    using (Graphics g = this.CreateGraphics())
    {
        // Get the current region for the window caption.
        if (SetRenderer(windowElements["windowCaption"]))
        {
            Region clipRegion = renderer.GetBackgroundRegion(
                g, elementRectangles["windowCaption"]);

            // Get the client rectangle, but exclude the region 
            // of the window caption.
            int height = (int)clipRegion.GetBounds(g).Height;
            Rectangle nonCaptionRect = new Rectangle(
                ClientRectangle.X,
                ClientRectangle.Y + height,
                ClientRectangle.Width,
                ClientRectangle.Height - height);

            // Add the rectangle to the caption region, and  
            // make this region the form's clipping region.
            clipRegion.Union(nonCaptionRect);
            this.Region = clipRegion;
        }
    }
}

' Calculate and set the clipping region for the control  
' so that the corners of the title bar are rounded.
Private Sub SetClipRegion()
    If Not Application.RenderWithVisualStyles Then
        Return
    End If

    Using g As Graphics = Me.CreateGraphics()
        ' Get the current region for the window caption.
        If SetRenderer(windowElements("windowCaption")) Then
            Dim clipRegion As Region = _
                renderer.GetBackgroundRegion(g, _
                elementRectangles("windowCaption"))

            ' Get the client rectangle, but exclude the   
            ' region of the window caption.
            Dim height As Integer = _
                CInt(clipRegion.GetBounds(g).Height)
            Dim nonCaptionRect As _
                New Rectangle(ClientRectangle.X, _
                ClientRectangle.Y + height, _
                ClientRectangle.Width, _
                ClientRectangle.Height - height)

            ' Add the rectangle to the caption region, and  
            ' make this region the form's clipping region.
            clipRegion.Union(nonCaptionRect)
            Me.Region = clipRegion
        End If
    End Using
End Sub

Remarks

This method can be used to get the Region of a visual style element that has partially transparent or alpha-blended parts in its background.