Hi, I was going to reply to the original, but Peter's reply says pretty much everything I wanted to say.
On Mon, Feb 23, 2009 at 10:29:42AM +1000, Peter Hutterer wrote: > On Sun, Feb 22, 2009 at 12:28:23PM -0500, Jim Gettys wrote: > > Here are some substantive issues: > > > > 1) I wonder how we can extend XI2 to deal with multiuser displays (with > > some sort of security between users), when we have enough experience to > > work out the details. Do we distinguish via the deviceid? If so, is 16 > > bits of deviceid enough? (allowing for 256 users of 256 devices, as a > > possibility...). Or is a separate user field for each device better? A > > device might someday be as simple minded as a playing piece on a > > chessboard (with sensors, for example). > > I don't think we should have the notion of a "user" in the protocol. X is (or > should be) an abstraction layer for input devices, the notion of a user (in > regards to input devices) is too context-sensitive to build into the protocol. > > Get the DE to label the devices through properties, and then apps to listen to > these properties correctly, similar to EMWH. The big advantage of this is that > a property-based protocol is easier to test and easier to modify than the wire > protocol. Or just do it through XACE. I mean, if you're after security, then surely you'd rather it was properly enforced through our existing security framework rather than hoping people respect the convention. > > ButtonClasses and DeviceClasses I'm worried. Here's why: Interning > > atoms require a round trip, and won't we end up with way too many types? > > And do we really want to be a registry for such names? Looking at the > > USB specs, there are *tons* of devices and various types. We thought > > we'd avoid this in the early X11 design by the "predefined atoms" stuff, > > but it didn't work out well in the end; it would have been better to > > just use strings and send them everywhere in the protocol. The registry > > headache is not to be undertaken lightly. Similarly, we're mostly out > > of the keysym business by punting most of it to the Unicode consortium. > > In regards to the atom worries: Not to mention that we can also make XInternAtoms do multiple atoms at a time with Fixes. > > o we could define a mapping between USB descriptors and XML events, > > and send all this as XML. This isn't entirely crazy. In fact, most > > events end up as XML inside browsers anyway. It is very extensible. > > There are binary versions of XML if we wanted to go this way; though > > care on design to avoid verbosity (and transmitting a data descriptor > > first (or on device change) and just the data is very possible). > > XML is merely a container format. It doesn't solve our actual problem - what > information to send to the client. Preach it, brother! Cheers, Daniel
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