Late reply from myself as well. My main laptop died last week and I've been offline more then normal as I recover from that. Replies below.
On Tue, Mar 16, 2010 at 12:40 AM, Ping Cheng <[email protected]> wrote: > Hi Chris, > > Sorry for my late reply. I was investigating a "decent" solution for MT > support. As you know backward compatibility is the major concern here. Is backwards compatibility really a concern in this case? It looks like tablet PC support got added around Oct. 2009 and only in developer releases of linuxwacom. It looks like tablet PC got merged to linux's tree around November 2009 so probably its in 2.6.33 which is a concern for compatibility reasons. But that original logic that made it into official kernel was fundamentally broken since it did not consider input filtering. I know exceptions are given to fix broken features... especially when a kernel blessed solution (multi-touch input) exists to fix the fundamental problem. Since Bamboo Pen&Touch support hasn't made it in any non-developer release yet, I'm assuming we have total freedom with it. > Replacing xxxTAP with _MT_ events at this stage requires both kernel and X > driver changes. Plus there are third party developers relying on us. Since > there are only two fingers, I think staying with xxxTAP is not too far off > the topic. To make events definition consistent for all tablet models, all > 2FGT touch devices will use xxxTAP. Future multi-touch devices will use > _MT_ event. wcmUSB.c will be redesigned to process those MT events in a > separate routine(s). I don't think third party apps are much a concern here because: 1) the old interface is broken and will show up in their app. Change to MT is proposing the solution to bugs they will see. 2) I don't think you were proposing implementing any real fixes to filtering issue for the xxxTAP events so apps that are forced to use xxTAP solution will always have use cases that have lost or invalid touch event data. Thats a dead end of app developers. I had hopes that we would not have a wacom specific solution for these non-pen /dev/input/event's since users will expect them to have standard touchscreen/touchpad behavior. Ideally, we should stay as close to xf86-input-evdev's generic device expectations as possible for both tablet PC's and Bamboo P&T's. There is not a lot of need to handle touch input events using xf86-input-wacom beyond the xxxTAP now-non-standard solution to exposing 2 finger data to input driver. I suspect it will be xf86-input-evdev that will have multi-touch support first (I mean exposing fingers to applications... not just the MPX stuff). We'd be wise to work with them for greatest-and-fastest user benefits. I recently sent a patch that could be made to support both MT and xxxTAP solution in kernel driver at same time. It works because MT input people considered backwards compatibility. Old apps will ignore MT events and just process old-but-broken ABS_X/Y/PRESSURE events. New MT-aware apps will disable ABS-X/Y/PRESSURE processing and only look at MT events. So you get best of both words, so to speak, except for need to send wasted events. Even this is a little ugly because its using DOUBLETAP and TRIPLETAP in ways that I'm sure no generic application (xf86-input-evdev) would expect... but at least when evdev becomes MT-aware it has a chance of working with them. Anyways, my opinion is we should switch everything to MT... but your making the calls. :-) Chris ------------------------------------------------------------------------------ Download Intel® Parallel Studio Eval Try the new software tools for yourself. Speed compiling, find bugs proactively, and fine-tune applications for parallel performance. See why Intel Parallel Studio got high marks during beta. http://p.sf.net/sfu/intel-sw-dev _______________________________________________ Linuxwacom-devel mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/linuxwacom-devel
