Window procedures in ScreenRec not populated by DDX driver. why?

[Pauli Nieminen]

On Tue, Feb 15, 2011 at 4:54 AM, kumar vemuri <kumar210in at gmail.com> wrote:
> Hi,
>
>   In most of the reference DDX driver implementations, the Pixmap procedures
> (CreatePixmap, etc) are being implemented by the driver and also are getting
> populated in the ScreenRec structure by the driver. But none of the Window
> procedures (like CreateWindow, DestroyWindow ...) are being implemented by
> the drivers.
>
> Can someone throw a hint as to why the Window procedures of ScreenRec are
> not being implemented by the driver whereas the Pixmap procedures are?
>
> (I checked with a couple of reference implementations and this is a common
> observation.)
>
> Thanks
> -K

CreatePixmap requires driver to allocate memory that is often
available for GPU to read and write. That requires driver specific
allocation scheme which makes it mandatory to implement CreatePixmap
in DDX driver. While CreatePixmap doesn't require any backing store
allocations. Allocation is done in composite/compalloc.c (if done at
all). If composite isn't used backing store is same as for root
window. Root window has pixmap allocated in server boot to hold
framebuffer memory.

Pauli