<div dir="ltr"> <div class="gmail_extra"><div class="gmail_quote"><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div> > The situation is getting even worse if you look at the feature which > Windows' Wacom driver has (I'm not sure whether this feature is available > in X11 Wacom driver, but it is highly requested by the painters). On > Windows the buttons on the stylus can be switched into "modifier" mode. > That is pressing the button doesn't produce a real button event. You need > to press the stylus button, and then touch the surface of the tablet with > the tip: only then the app will get mouse button click (right or middle > button usually). If this feature will ever be implemented in X11 Wacom > driver (which is quite desirable), your protocol with TabletTouch/Press > will not work. Please check Wintab protocol docs for more info, > specifically, CSR_SYSBTNMAP attributes [0] </div>are you talking about Option TPCButton? it does what you describe above, and the earliest reference in the linuxwacom driver I can find for it is 2003 :) </blockquote><div> </div><div>Probably, yes. How the semantic of TabletTouch/Release will work in that case? Technically, a TabletTouch event will have to be sent on each button pressed, won't it? </div><div> </div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"> <div> > 3) Axes resolution. Yes, it is perfectly ok to have a separate function > which tells the physical limits of the axis. What I wanted to say is that > min_value/max_value attributes, which are reported by XInput are not > enough. For rotation I also need to know the mapping of the coordinate > system origin and it's direction (clockwise/counterclockwise). </div>we're planning to have this well defined for the protocol so that these things can be relied upon. Cheers, Peter <div><div> > > PS: > Please keep me in CC, I'm having troubles with keeping up with the traffic > in this mailing list. > > > [0] - <a href="http://www.wacomeng.com/windows/docs/Wintab_v140.htm" target="_blank">http://www.wacomeng.com/windows/docs/Wintab_v140.htm</a> > > > > On Fri, Jun 27, 2014 at 6:53 AM, Jason Gerecke <<a href="mailto:killertofu@gmail.com" target="_blank">killertofu@gmail.com</a>> wrote: > > > On Wed, Jun 25, 2014 at 5:50 PM, Peter Hutterer > > <<a href="mailto:peter.hutterer@who-t.net" target="_blank">peter.hutterer@who-t.net</a>> wrote: > > > Replying to three emails at once here to keep the thread a bit more > > > managable. > > > > > > On Wed, Jun 25, 2014 at 01:38:22PM -0700, Jason Gerecke wrote: > > >> On Wed, Jun 25, 2014 at 12:38 AM, Lyude <<a href="mailto:thatslyude@gmail.com" target="_blank">thatslyude@gmail.com</a>> wrote: > > >> > On Wed, 2014-06-25 at 11:06 +0400, Dmitry Kazakov wrote: > > >> >> Hi, all! > > >> >> > > >> >> > > >> >> I am a developer from Krita painting application team. We recently > > did > > >> >> quite much work on incorporating better tablet support in Krita. I > > >> >> have several comments about your proposal of the tablet protocol > > >> >> (sorry for nor replying directly, since I wasn't subscribed to the > > >> >> list before). > > >> > > > >> > Benjamin commented on this as I was writing this e-mail, and I > > figured I > > >> > should too: yes, it's awesome to see developers commenting on the > > >> > protocol. A lot of the quirks around this protocol are going to be > > >> > difficult to see without the help of people who have programmed on the > > >> > client side of things as opposed to the compositor side of things. So > > >> > yes, your input is very much appreciated and I thank you for it! > > >> > > > >> >> > > >> >> 1) Axes. There should also be an axis for rotation of the stylus > > >> >> (Artpen) and Tangential Pressure (for the wheel of the Airbrush). > > >> >> > > >> >> 2) There is also Artpen type of stylus. In Qt it is called > > "Rotational > > >> >> Stylus". > > >> > > > >> > Don't worry, we haven't forgotten about these. These will eventually > > be > > >> > added into the protocol. The reason why they're not in this draft is > > >> > because I'm doing this as my Google Summer of Code project, and as > > such > > >> > I'm on a deadline and I have to focus on just getting the basics done > > >> > first before I can focus on all of the other features. > > > > > > Our current approach, both in libinput and the WL protocol should make > > these > > > additions little more than adding a couple of enum, so I think we're good > > > here. > > > > > >> >> 3) Fingers. There is a complication in XInput2 right now, since touch > > >> >> enabled Wacom devices have a special Finger XInput2 device, which > > >> >> provides both interfaces: tablet and touch and therefore generates > > >> >> both types of events. Right now Qt5 still cannot handle it properly, > > >> >> but the work is in progress. From Krita point of view, the main > > >> >> usecase for us is to distinguish whether the user paints with a > > finger > > >> >> of with the stylus. Because most of the users prefer to disable > > >> >> painting with fingers and use it for gestures/UI only (yes, palm > > >> >> detection works with non-100% probability). > > >> > > > >> > Right now libinput handles the finger device as another touchpad, > > since > > >> > that's usually what it is. Your use-case sounds perfectly valid > > though, > > >> > but IMO a better approach would be to add something to the protocol > > for > > >> > touchpads on wayland so that it can be known that they belong to a > > >> > tablet and provide any other sorts of data you might be need, so > > >> > programs like yours can treat them differently. > > > > > > Dmitry, are you talking about pen/touch arbitration, i.e. don't send > > touch > > > events when the pen is in use. If so, that's definitely on the plan, we > > need > > > it for touchpads (disable while typing feature), and we need it for the > > > pen/touch interference. > > > > > > This will be hidden away so you or event the compositor don't have to > > worry > > > about it. > > > > > >> >> 4) Button Press/Release events should come in both cases: when the > > >> >> user clicks on the stylus' buttons and when the stylus touches the > > >> >> surface of the tablet. > > >> > > > >> > I'm not entirely sure that's a good idea. If I'm reading this right, > > you > > >> > mean that additional button presses should be sent when the tool > > touches > > >> > the surface of the tablet. [...] > > > > > > We're already sending out BTN_TOUCH when the tip touches the surface, so > > I > > > think we're good here. Unless Dmitry was referring to something else. > > > > > > > > >> >> 6) It might be a good idea to define the physical properties of the > > >> >> axes. E.g. for tilt, rotation and tangential pressure. Afair, Wacom > > >> >> driver for XInput returns some not-very-obvious values right now. One > > >> >> would need to experiment to know what these numbers mean. > > >> > > > >> > We would all love for this to be the case I promise you, but > > >> > unfortunately it's not that simple for all of the axes. The distance > > >> > axis reports a seemingly meaningless value that can't be converted to > > >> > millimeters very easily. That being said, I have come up with a few > > ways > > >> > that we could actually convert it to millimeters, but this will have > > to > > >> > wait until I've fulfilled the goals for my Google Summer of Code > > Project > > >> > (unless anyone else wants to implement this in the mean time in > > libinput > > >> > of course). > > >> > > > >> > I'll write up the method I've come up with for converting this wild > > >> > value to actual millimeters at some point when I get the chance. > > >> > > > >> While I'm interested in seeing what you've come up with, I would be > > >> very hesitant to integrate the code into libinput. We make *no* claims > > >> about the physical resolution or accuracy of the distance axis. I've > > >> seen the value change by more than 10 units just by switching to a > > >> different pen... There's absolutely nothing stopping us from > > >> introducing a tablet that invalidates any clever code you may come up > > >> with. > > > > > > yeah, I agree with Jason here, let's not pretend we have data we don't > > have. > > > As much as I'd like to attach concrete physical information to all axes > > we > > > can't (well, shouldn't) make it up. > > > > > > Short of keeping a database of each tablet with the offsets and ratios to > > > convert distance values to mm I don't think this is doable, and I'm not a > > > big fan of that either. > > > > > >> > As for the tilt axes of the tools, this is something that could be > > >> > represented in a more meaningful value. We could normalize it to a > > >> > number between 0 and 180°, so you can get the actual tilt in degrees > > as > > >> > opposed to what we currently have. This is something we could pull off > > >> > rather easily, I'll make sure to discuss this with my mentor tomorrow. > > >> > > > >> Alternatively, I would suggest adding an e.g. > > >> `libinput_event_tablet_get_axis_resolution` function. To get a > > >> physical value, a caller would just multiply whatever this function > > >> returns for some axis by the current normalized unitless value for the > > >> same. I suggest this for a few reasons: it is a fairly standard way of > > >> doing things (HID, the kernel, and X all use the same system), is more > > >> efficient (callers working in your preferred unit [e.g. Qt] are spared > > >> doing the conversion but anyone else [e.g. GTK, EFL] will have to do a > > >> second conversion to a different unit), and provides a way of getting > > >> physical information for any axis (if we ever came out with a pen that > > >> accurately measured distance, you wouldn't need to change the > > >> semantics of how distance is reported or sacrifice the now-existant > > >> physical translation information). > > > > > > Jason: how accurate is tilt, and are applications actually using it as > > angle or > > > just as normalized number anyway? > > > > > > > I can't find a mention of the accuracy in any public docs, so I'm a > > little hesitant to give numbers on the list. The spec sheet does show > > it to be accurate to a handful of degrees though. > > > > The second part is a little complicated to answer. Every tilt-enabled > > program I'm aware of uses the data to adjust the brush azimuth. The > > goal is to have the virtual brush angled to be parallel with the > > physical pen at all times. A few applications also calculate an > > altitude angle, deforming the brush from circular to increasingly > > eliptical as the pen becomes more horizontal. Qt and Android (and > > likely EFL based on current discussions) have APIs that specify angles > > in various physical forms: tilt-x/tilt-y in degrees, alt-az in > > radians, etc. GTK on the other hand provides normalized data, but > > neither provides resolution information nor information about what > > "normalized" means. Because of the resulting ambiguity, GIMP and > > Inkscape do their calculations on the assumption that [-1, 1] in GTK > > corresponds to [-180 degrees, +180 degrees] in the physical world. GTK > > actually does its normalization based on the device's min/max though > > (so [-64 degrees, +63 degrees] for our hardware) meaning that GIMP and > > Inkscape wind up calculating incorrect azimuth values. The results > > aren't _that_ wrong though; I'm not aware of anyone having noticed or > > filing a bug about it. > > > > tl;dr, Applications universally /try/ to use the physical angles. Not > > all succeed. > > > > Jason > > --- > > Now instead of four in the eights place / > > you’ve got three, ‘Cause you added one / > > (That is to say, eight) to the two, / > > But you can’t take seven from three, / > > So you look at the sixty-fours.... > > > > >> > As for tangential pressure, this is a term I've never actually heard > > of > > >> > before. I don't know what the values from the tablet are supposed to > > >> > correspond to in regards to pressure, so I've added two of our friends > > >> > at Wacom to the CC list help us out (I hope you two don't mind!) on > > >> > this. > > >> > (Jason and Ping, if you guys aren't on the list already, the original > > >> > protocol this e-mail is discussing can be found here: > > >> > > > <a href="http://lists.freedesktop.org/archives/wayland-devel/2014-June/015583.html" target="_blank">http://lists.freedesktop.org/archives/wayland-devel/2014-June/015583.html</a> > > >> > ) > > >> > > > >> > In regards to rotation and any other axes, I haven't had any contact > > >> > with these yet. So I can't really say much on them. > > > > > > Rotation exists on the mouse/lens cursor tool, but it's a calculation > > based > > > on the tilt x/y axes. For us it'd just be one more axis. > > > > > > Cheers, > > > Peter > > > > > >> I'm not sure where the term "tangential pressure" came from, but it > > >> can refer either to the fingerwheel on the airbrush tool (expected to > > >> be used to control ink flow rate; value is basically [0, 1]) or the > > >> fingerwheel on the 4D Mouse tool (which is like a spring-loaded > > >> mousewheel that reports how far forward or backward from the neutral > > >> position the wheel is; value is basically [-1, 1]). > > >> > > >> Jason > > > > > > > > > -- > Dmitry Kazakov </div></div></blockquote></div> -- Dmitry Kazakov </div></div>