Multi OpenGLControls in WPF window

Oct 31, 2013 at 4:03 PM
Edited Oct 31, 2013 at 4:05 PM
I have two OpenGLControls in WPF window.

After running application one OpenGLControl is rendered, while the other is not.
Image 1

But after window resizing both controls are rendered. Why?
Why I need to resize window to display rendering in both controls
Image 2

I've reproduced such weird behavior using TeapotSample in WPF samples.