What does ToolStripProfessionalRenderer.OnRenderItemBackground do?

Question

I am writing a custom ToolStripProfessionalRenderer component and currently working through all of the OnRender... overrides.

This one in particular has stumped me: OnRenderItemBackground

I can't see it drawing anything, so to force it to draw something I've done this:

protected override void OnRenderItemBackground(ToolStripItemRenderEventArgs e)
{
    e.Graphics.FillRectangle(Brushes.Red, e.Item.ContentRectangle);
}

...but I don't see any red rectangles, so not sure what it's doing!?

Answer 1

All the stock ToolStripItems you can add with the designer already render their own background. So what you draw with your OnRenderItemBackground() override is immediately over-painted again. So ProfessionalToolStripRender simply doesn't override the method since nothing needs to be done. The base class method, ToolStripRender.OnRenderItemBackground(), doesn't do anything either.

Note OnRenderButtonBackground(), OnRenderDropDownButtonBackground(), OnRenderLabelBackground(), etcetera.