Got empty clipRect in NPP_SetWindow while resizing

Hi all,

I am new to firefox plugin developement and currently working on a video plugin for firefox 4.0.1.

One thing I noticed is that when resizing the firefox window, the plugin sometimes gets NPP_SetWindow with a valid window but empty clipRect.  For example, the clipRect=(286,119,286,119).  The width and hight of the clip rect is 0.  As a result, sometimes after resize, the video get empty.  Does anyone know under what conditions, the empty clipRect can be passed down to the plugin?

Thanks!