nanogui: Thread: Flicker over the screen

Hello,
I am facing one issue, when I draw a menu UI using nano-X lib... as follows:

1. Drawn a rectangle(Menu Box) and then Three Square Buttons (e.g.
Brightness, Sharpness, Hue Control).
2. Waiting for a key event as Up/Down.
3. The present user selected button becomes active (e.g. Red fill color).
The previous button becomes inactive (e.g. Grey Fill Color).
4. During this above process, I clear the entire Menu Box and buttons and
need to redraw the UI boxes with current active button box. 

---> So This simple draw when I port it on my Cirrus target platform
(EDB9307A)....... I see there is flicker due to this "Clear Operation" and
"Redraw operation". Looks like there is some unknown delay which is getting
reflected this way. But my code sequence I very straight forward.. and
simple.

PLEASE SUGGEST ME ... HOW CAN I OVER COME THIS ISSUE.

> I see there is flicker due to this "Clear Operation" and
: "Redraw operation". Looks like there is some unknown delay which is 
getting
: reflected this way. But my code sequence I very straight forward.. and
: simple.

A basic mechanism to stop flickering is to double buffer all output,
which means drawing into an offscreen pixmap and then copyarea
that to the screen once.

Your code sequence may be straight forward and simple,
but if it over draws the same area twice (especially including
automated background clearing) then you're apt to see flicker
except for very fast systems.

Regards,

Greg