Hi, First of all, I'm sorry I dropped the ball this long. It's great to see you've been doing some progress.
On jue, 2014-05-22 at 01:17 -0400, Chandler Paul wrote: > Hi! Sorry this took so long to write, I've been spending a lot of my > time recently trying to understand the libinput code and all of that > good stuff, and I wanted to make sure I had a decent understanding of it > before I actually wrote up a response. > > On Mon, 2014-04-21 at 19:11 +0200, Carlos Garnacho wrote: > > Hey there!, > > > > Here's a few patches to have libinput handle events from tablets, > > these devices are basically pointer devices, with a varying range > > of extra buttons (either stylus or "pad" buttons), and extra ABS_* > > axes. These devices also often offer information about the stylus > > in use, and its BTN_TOOL_* codes. > > > > So I've gone for reusing and extending libinput_event_pointer, adding > > extra libinput_pointer_axis values, and adding an "axis_frame" event > > to mark the end of a set of simultaneous axis changes, and a "tool_update" > > event to mark tool changes (and delimit proximity). These features are > > only triggered if a new LIBINPUT_DEVICE_CAP_STYLUS capability is set. > I'm with Peter on splitting these up. It seems kind of inconsistent with > the rest of libinput (with what I've gathered, anyway). A > tablet-specific event sounds interesting too, but I feel like > compressing all of the axis changes into. For now I'm going to work on > having all the axis changes reported as separate POINTER_AXIS events. I'm not against making this a separate set of event types. I would advise though against attempting to compress axis changes into a single event, it puts certain processing burden on clients, and most of those not always want as much data. Independently of this being a separate set of events, IMO the axis frame event is still useful for pointer events, this might help compressing the processing of dx/dy for scrolling in clients for example, instead of processing 2 events that queue the redraw of different areas, some unneeded in the end. > > > > > Caveats: > > > > * Many of these devices have also tactile strips or wheels, but these are > > unhandled so far... On the devices I've got available for testing, > > current > > kernel support seems varyingly inconsistent: > > > > - One device has 2 strips, which report on ABS_RX/RY (radial??). Min/max > > are 0..4096, but the reported values are 1,2,4,8,16... So effectively > > a log2 scale, or more graphically a bit shifting over a bunch of 0s, > > which is somewhat more resembling to the physical action on the strip. > Since I'm on a deadline for this and making changes to this in the > kernel would take too long, I don't think I'm going to advocate for > changing this behavior right now. Although I do agree that eventually it > should be changed. Graphically, a bit moving across a field like that > makes sense, but I think that would be a difficult value to make > practical use of in an application without changing it to a simple 1-13 > value. If I get far enough that I can start implementing support for > tactile strips and all those other fancy features some of these tablets > have I might have it convert the values for tactile strips like that to > something more usable by default and leave the other axes as-is. I'm > curious to hear Ping and Jason's opinion on this though, and what kind > of advantages > > > - Another device has one wheel, reported through ABS_WHEEL. Even though > > min/max are reported as [0..1023], on interaction it goes [0..71] (funky > > range too) > > > > We could just forward this as-is, but seems hindering enough to do > > anything > > useful with those unless that behavior is corrected. > > > > When supported, IMO it'd make sense to have those axes behave similar to > > scroll axes, so the axis value increments or decrements depending on the > > direction. I'm not sure if there would be cases where the absolute value > > matters here? > > > > * One thing worth noting is that axes are currently normalized, to [-1..1] > > for stylus tilt, and [0..1] for everything else. I remember Peter's > > tablet wayland protocol proposal basically forwarded input_absinfo, this > > might not be fully compatible with that, although TBH I'm unsure > > clamping/normalization should take place so high in the stack... > I'm with Peter on this actually. If the axes were used for something > else I might approve of normalization in libinput but I think having > absolute values fits more of the use cases for the extra axes found on > many tablets, especially since Ping said that some of Wacom's in-house > applications actually need these. I do think however, that maybe we > should consider clamping axis values with libinput even if we don't > normalize the axes by default. > > I've forked libinput and I have a branch where I'm fixing up the patches > Carlos sent in based on the feedback from Peter. You can find it here: > > https://github.com/Lyude1337/libinput/tree/carlos_cleanup Thanks for the cleanup and appliying the recommended fixes, the changes look good so far. > > The history is messy on this, but once this is ready to get sent in as > actual patches I'll be rebasing the history. > > Right now I've removed normalization from my branch, but if someone > brings up a good reason to actually have libinput handle that then I can > revert the change. I agree, this should just probably be some helper code. Cheers, Carlos _______________________________________________ wayland-devel mailing list [email protected] http://lists.freedesktop.org/mailman/listinfo/wayland-devel
