XRandR rotate support HW rotate or not?

[Alex Deucher]

2008/10/31  <FloraGui at viatech.com.cn>:
> Dear Keith Packard：
>
>       I have recently study RandR,  I found if we use RandR rotate no matter
> static rotate or dynamic rotate，we always use RandR's own software rotate.
>
>       We draw the screen desktop very slow,  how can we support HW rotate
> using RandR or it is a RandR limitation, if it is, RandR1.3 has support HW
> rotate or not ?

Your driver needs to implement the EXA composite hook with support for
transforms and the randr 1.2 shadow_create/allocate/destroy hooks.
The basic idea is that when you elect to rotate your screen, a shadow
framebuffer is allocated in the randr core code calling the driver
shadow* hooks to allocate a buffer for the rotated screen.  The crtc
is then pointed to this shadow buffer.  The randr core code then uses
the driver's EXA composite hook to transform the regions that are
damaged and display them in the shadow buffer.  Both the Intel driver
and the radeon driver implement this.

Alex