Hi, all! I'd like to add about mapping of the tablet input.
In XInput one can assign a matrix transfromation for each tablet device, which is exactly what people need. The usual usecase is the following: A painter has a display + intuos tablet + cintiq. The external tablet is mapped to the external display, the Cintiq, obviously, is mapped into itself [0]. The external display can be (and probably will be) rotated on 90deg to have Portrait orientation. Right now all the mappings for such configuration can be achieved with xsetwacom/xinput calls. [0] - No painters I know use mappings to the specific window. Mode switches are troublesome. On Mon, Jun 30, 2014 at 11:41 AM, Dmitry Kazakov <[email protected]> wrote: > Hi, all! > > I will try to answer all your emails in one post. > > 1) Tablet vs. Touch. Basically what I am talking about is *not* touch > arbitration and palm recognition. The Wacom driver itself blocks all the > touch events when the stylus is in the proximity, so it performs the > necessary arbitration. What we need is to block several kinds of actions > (read "tools") when the user uses touch and unblock them when the user > works with stylus or mouse. An exact usecase: we need to allow the user to > zoom/pan on the canvas with his fingers, but at the same time real painting > with fingers must be prohibited (it disturbs the painters). Right now it is > almost impossible, because we get no touch events, and instead get > synthesized MousePress/Release/Move events for finger actions, which are > indistinguishable from real mouse events. > > 2) Buttons vs Tablet Press. Well, to tell you the truth we are not > interested in whether the stylus touched the surface of not. At all. The > stylus has 3 button: the tip itself, and two buttons. These three buttons > can be remapped with the driver (xsetwacom) to any X11 button the user > wants. Therefore, I have absolutely no interest in > TabletTouch/TabletRelease if the only thing they tell me that the stylus > has touched the surface of the tablet with the stylus or not. What I really > need is the TabletButtonPress/Release event, which tells me: > > 1) Which button (of the three) is pressed > 2) Exact position of the stylus > 3) Pressure, Tilt, Z-coordinate if available (might be zero/unit for some > of the buttons) > > 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] > > 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). > > PS: > Please keep me in CC, I'm having troubles with keeping up with the traffic > in this mailing list. > > > [0] - http://www.wacomeng.com/windows/docs/Wintab_v140.htm > > > > On Fri, Jun 27, 2014 at 6:53 AM, Jason Gerecke <[email protected]> > wrote: > >> On Wed, Jun 25, 2014 at 5:50 PM, Peter Hutterer >> <[email protected]> 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 <[email protected]> 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: >> >> > >> http://lists.freedesktop.org/archives/wayland-devel/2014-June/015583.html >> >> > ) >> >> > >> >> > 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 > -- Dmitry Kazakov
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