OnRenderButtonBackground Method

ToolStripRenderer.OnRenderButtonBackground Method (ToolStripItemRenderEventArgs)

 

Raises the RenderButtonBackground event.

Namespace:   System.Windows.Forms
Assembly:  System.Windows.Forms (in System.Windows.Forms.dll)

protected virtual void OnRenderButtonBackground(
	ToolStripItemRenderEventArgs e
)

Parameters

e
Type: System.Windows.Forms.ToolStripItemRenderEventArgs

A ToolStripRenderEventArgs that contains the event data.

Raising an event invokes the event handler through a delegate. For more information, see Handling and Raising Events.

The OnRenderButtonBackground method also allows derived classes to handle the event without attaching a delegate. This is the preferred technique for handling the event in a derived class.

Notes to Inheritors:

When overriding OnRenderButtonBackground in a derived class, be sure to call the base class's OnRenderButtonBackground method so that registered delegates receive the event.

The following code example demonstrates how to override the OnRenderButtonBackground method to draw a border around a ToolStripButton control's Image. This code example is part of a larger example provided for the ToolStripRenderer class.

// 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 override void OnRenderButtonBackground(
    ToolStripItemRenderEventArgs e)
{
    base.OnRenderButtonBackground(e);

    // Define some local variables for convenience.
    Graphics g = e.Graphics;
    GridStrip gs = e.ToolStrip as GridStrip;
    ToolStripButton gsb = e.Item as ToolStripButton;

    // Calculate the rectangle around which the border is painted.
    Rectangle imageRectangle = 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 == gs.EmptyCell)
    {
        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.
        Brush b = gs.IsValidDragSource(gsb) ? b = 
            Brushes.Red : SystemBrushes.ControlDarkDark;

        // Draw the top segment of the border.
        Rectangle borderSegment = 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);
    }
}

.NET Framework
Available since 2.0
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