Sprite transforms in RandR

Keith Packard keithp at keithp.com
Mon Dec 6 10:07:40 PST 2010

On Mon, 6 Dec 2010 09:42:24 -0800, Aaron Plattner <aplattner at nvidia.com> wrote:
> On Mon, Dec 06, 2010 at 08:44:41AM -0800, Keith Packard wrote:
> > On Mon, 6 Dec 2010 15:20:01 +0000, Daniel Stone <daniel at fooishbar.org> wrote:
> > 
> > > Nope, we don't have any per-CRTC differences there, it's just that
> > > rotation is essentially another property of the mode that we need to know
> > > about in order to set up both the CRTC and the underlying surfaces,
> > > rather than an additional BlockHandler and a transform somewhere.
> > 
> > If we don't have any existing hardware which requires per-CRTC scanout
> > formats, I have to admit I'm tempted to leave the interface alone
> > instead of making things more complicated for both applications and the
> > server.
> Are there really no dumb little phones or something that can rotate the
> internal screen but not external displays?  I'd feel more comfortable if
> someone familiar with the various embedded graphics chips would chime in
> with an ack/nack.

That's why I asked Daniel -- he was dealing with a phone that had
hardware rotation support (some OMAP thing), and he says that the
hardware will rotate on any CRTC (it's got TV out).

> I guess outputs have a mask of allowable rotations provided to the clients.
> Maybe that's sufficient: you can only use hardware rotation if the
> scanoutpixmapinfo *and* the corresponding output rotation mask say you can,
> and otherwise you get to do the rotation yourself with the graphics
> hardware?

Right. The question is only whether separate outputs need *different*
scanout pixmap formats.

> One thing that reminded me of is how the requested rotation is going to be
> communicated to the compositor.  Should we add something like a
> RRConfigRedirectMask, or will the clients be expected to invent their own
> new protocol for sending configuration requests to the compositor?

I wonder how it works today; I've got a phone that appears to allow
applications to rotate the screen, do they actually have applications
doing the RandR calls?

Sounds like we might want to consider adding a configuration redirection
mechanism at some point...

keith.packard at intel.com
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