Device Properties Protocol Spec - Draft 1

[Peter Hutterer]

On Sun, Sep 07, 2008 at 04:13:18PM +0200, Tomas Carnecky wrote:
> Peter Hutterer wrote:
> > On Sat, Sep 06, 2008 at 05:15:51PM -0700, Keith Packard wrote:
> >> On Sat, 2008-09-06 at 17:23 +0300, Daniel Stone wrote:
> >>
> >>> Isn't this just PropModeReplace with nItems = 0?
> >> Is there a difference between a property of length zero and an absent
> >> property?
> > 
> > nItems = 0 remove the content, but not the property itself, hence the need for
> > DeleteProperty. This is also the behaviour core has with window properties.
> 
> What is the difference between a property with no content and no
> property? In which situations would this distinction be useful?

An empty property indicates that e.g. the driver knows about this property,
but no data is available (or can be exported).

Cheers,
  Peter