change X-window only draw on damage

[Jason Wu]

Hi, i am using display link's x-window driver as reference, trying to write
my own

looks like displaylink's x-window driver, is only drawing (triggering)
defered_io to the driver,
when there's something moving or change on the screen,

is there anything i can do, to change to always renew all screen?
so my video hardware driver can keep drawing things coming from x-window.

here's my machine info
uname -r
3.2.9-2.fc16.i686
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