Issue that window is blinking when resizing.

[ghlab]

Hi.
I try to resize frameless window so make simple sample on my mac(osx 10.9.1) computer.
It works fine but the window is blinking when resizing.
Please watch this video. "http://www.youtube.com/watch?v=svupG2u4rns":http://www.youtube.com/watch?v=svupG2u4rns
The windows's background color is black but sometime it is changed as white.
How can I solve this problem?
Please let me know.

You can download the sample I made : "http://www.ghlab.com/temp/resizing_sample.zip":http://www.ghlab.com/temp/resizing_sample.zip