[RFC PATCH] Add XI_PROP_ROTATION property to the server's properties.

Daniel Stone daniel at fooishbar.org
Tue Mar 22 22:37:22 PDT 2011

Thinking out loud ...

On Wed, Mar 23, 2011 at 03:13:55PM +1000, Peter Hutterer wrote:
> Having rotation support has been a feature requested for a while
> now. Now we've had two independent implementations happen within quite a
> short timeframe, one in synaptics, one in evdev (and wacom has had it's own
> implementation for a while). So the question is now, how to do this best.
> We have the transformation matrix in the server which can be used to rotate
> absolute devices. But it's not yet suited for relative devices and I'm not
> 100% sure it's a trivial task to do so.
> The alternative is a separate transformation property. To unify this, I'd
> like to see this property defined by the server (but not necessarily
> implemented by the server). Since different devices have different
> requirements (e.g. synaptics may only allow rotation in 90 deg angles) it
> seems best implemented by the driver.
> Of course, the exact semantics of where this property fits in have to be
> documented to avoid nasty surprises, but that'll happen in the final version
> of this patch then.
> Does that make sense?

I had in mind two properties: a CRTC ID which would bind the input
device to the given CRTC (so, for absolute devices, map the area to the
CRTC area), and another bool which would follow that CRTC's transform.
So, if you had a touchscreen, you could just give it an absolute CRTC
binding and have it always follow the CRTC's transform to get rotated
co-ords, etc.

We might still need an explicit rotation property though.  But yeah.

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