Investigate if tangentialPressure is correctly implemented/working in browsers/documented appropriately in spec

[patrickhlauke]

Related to the initial email I sent to the list about the Wacom airbrush pen https://lists.w3.org/Archives/Public/public-pointer-events/2023JanMar/0041.html which now led me down a strange rabbit hole.

Wondering if we could spend some time:

• checking if/how the behind-the-scenes plumbing in Chrome/Firefox has been done, and whether it's correct or not (not spec-related)
• whether or not we may need to add some more information/description to our definition https://w3c.github.io/pointerevents/#dom-pointerevent-tangentialpressure (spec-related)

Related links/issues

• where tangentialPressure was first mentioned by @dfleck and what HID value it uses Add additional digitizer/pen attributes: twist (rotation) #25 (comment)
• PDF version of the HID specification https://www.usb.org/sites/default/files/documents/hut1_12v2.pdf (at least I think this is the relevant/most up-to-date one)
• Apple's tangentialPressure documentation https://developer.apple.com/documentation/appkit/nsevent/1525959-tangentialpressure (which solidified our choice for the name/decision to actually implement this in spec)
• split-out issue to add tangentialPressure to the spec Add additional digitizer/pen attributes: barrel pressure (tangential pressure) #70
• actual PR that added tangentialPressure Add digitizer/pen tangential (barrel) pressure #87
• a check on browser implementation of tangentialPressure, and @mustaqahmed's comment about it shipping tangentialPressure support in browsers #192 (comment)

(and for reference, the Wacom Airbrush Pen https://estore.wacom.com/en-US/wacom-airbrush-pen-kp400e2.html - note the "finger wheel" feature)

[patrickhlauke]

Note that for testing, you should be able to use https://patrickhlauke.github.io/touch/pen-tracker/ (i've hooked it up to show tangentialPressure as a value once you start interacting with the demo using a tablet/pen)

[patrickhlauke]

@mustaqahmed @smaug---- let me know if I should explicitly file bugs anywhere about this (presumably in https://bugs.chromium.org/p/chromium/issues/list and https://bugzilla.mozilla.org/ respectively), or if you're happy (?) to check internally first

[patrickhlauke]

also, some more info on how the finger wheel is actually used: in essence, it's just an additional sensor on the airbrush, and does not replace pressure. users generally map/remap what it does in applications - by default, I believe that apps like Photoshop have the wheel mapped to pressure (changing opacity, so essentially replacing the purpose of tip pressure, which is then ignored/not mapped to opacity anymore), but it's up to users - some remap it so that tip pressure still affects the usual opacity of a stroke, and the wheel is used to set brush size for instance.

[smaug----]

https://bugzilla.mozilla.org/show_bug.cgi?id=1372097 says it was implemented on Firefox/Mac, and I don't see any code for it on non-Mac platforms.

[patrickhlauke]

@smaug---- @mustaqahmed following on from our quick discussion at today's meeting, I can confirm that tangentialPressure is actually handled correctly on Chrome/macOS and Firefox/macOS - so the problem may be in the integration for Windows (not able to test for Linux at this point)

Safari/macOS does not currently recognise the Wacom stylus as an actual pen device, and just reports it as mouse. I guess it's a long shot to ask if @graouts is in a position to share if there's an intention of implementing this in webkit or not...

[patrickhlauke]

(incidentally, @smaug---- ... found a bug with Firefox/macOS and its tiltY while testing this https://bugzilla.mozilla.org/show_bug.cgi?id=1822714)

[mustaqahmed]

On Windows, did you mean it's broken on both Chrome and Firefox?

Too many variations here, it would be nice to have a table of impl status across [major browsers] x [major OSes].

[patrickhlauke]

@mustaqahmed on Windows, tangentialPressure shows just 0 in both Chrome and Firefox. On macOS, tangentialPressure works correctly in Chrome and Firefox. all with latest stable release OS and browser version.

macOS/Safari doesn't even know what a pen device. it recognises the Wacom stylus just as a mouse, and tiltX, tiltY, tangentialPressure, pressure are all 0

[patrickhlauke]

@mustaqahmed remind me...is there a chrome bug about this tangentialPressure on Windows already, or do you want me to file one?

@smaug---- similar question...is there already a firefox bug for this on Windows, or do you want me to file one too?

[mustaqahmed]

I couldn't find any existing Chromium bug, looks like we need to file one at crbug.com/new.

[patrickhlauke]

I'll get on that later tonight, @mustaqahmed

[patrickhlauke]

@mustaqahmed filed a bug against Chrome https://bugs.chromium.org/p/chromium/issues/detail?id=1426685

@smaug---- ditto for Firefox https://bugzilla.mozilla.org/show_bug.cgi?id=1823822