[Webkit-unassigned] [Bug 206216] PointerEvent has 0 as pressure when the input device is not pressure-sensitive

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=206216

--- Comment #6 from Akihiko Odaki <nekomanma at pixiv.com> ---
(In reply to Darin Adler from comment #3)
> Comment on attachment 388210 [details]
> Patch
> 
> View in context:
> https://bugs.webkit.org/attachment.cgi?id=388210&action=review
> 
> > Source/WebCore/dom/PointerEvent.cpp:115
> > +    , m_pressure(mouseEvent.buttons() ? 0.5 : 0)
> 
> I am not 100% sure this is right. The specification calls for all pointerup
> events having pressure of 0. Are we guaranteed that buttons() will be 0 for
> *all* pointerup events? The test case covers only a simple case of a mouse
> with a single button.

Yes, the specification states:
> A user agent MUST fire a pointer event named pointerup when a pointer leaves the active buttons state.

> 
> > LayoutTests/ChangeLog:11
> > +        * pointerevents/mouse/pointer-button-and-buttons-expected.txt: Removed.
> > +        * pointerevents/mouse/pointer-button-and-buttons.html: Removed.
> > +        * pointerevents/mouse/pointer-button-buttons-and-pressure-expected.txt: Added.
> > +        * pointerevents/mouse/pointer-button-buttons-and-pressure.html: Added.
> 
> Why are we renaming this test case?

Because it is now testing pressure property too. The name simply represents tested properties.

(In reply to Darin Adler from comment #4)

> (In reply to Akihiko Odaki from comment #0)
> > Apparently, WebKit refers to pressure property of NSEvent. The documentation
> > states:
> > > For input devices that aren’t pressure-sensitive, the value is either 0.0 or 1.0.
> > https://developer.apple.com/documentation/appkit/nsevent/1534543-pressure
> 
> Aside from the bug fixed here, this implies that on *Cocoa* platforms, for
> non-pressure-sensitive devices, WebKit is setting 1.0 as the pressure, where
> the standard instead requests/requires that we set it to 0.5. May be
> challenging to fix if NSEvent does not tell us whether the device is
> pressure-sensitive. It would be good if someone investigated this and
> created tests.

I wrote that statement before carefully looking at the code and it is misleading. In reality, pressure property of NSEvent is completely ignored because MouseEvent provided to PointerEvent to create a new instance does not have pressure information.

(In reply to Antoine Quint from comment #5)
> (In reply to Darin Adler from comment #3)
> > Comment on attachment 388210 [details]
> > Patch
> > 
> > View in context:
> > https://bugs.webkit.org/attachment.cgi?id=388210&action=review
> > 
> > > Source/WebCore/dom/PointerEvent.cpp:115
> > > +    , m_pressure(mouseEvent.buttons() ? 0.5 : 0)
> > 
> > I am not 100% sure this is right. The specification calls for all pointerup
> > events having pressure of 0. Are we guaranteed that buttons() will be 0 for
> > *all* pointerup events? The test case covers only a simple case of a mouse
> > with a single button.
> 
> Maybe it would be better to use the provided event type to set the pressure
> value.

The specification states it is guaranteed, so I do not think it makes difference. We can still add an assertion, but such an assertion should cover all (including one generated by pressure-sensitive device) PointerEvents and I think it is out of scope of this bug.

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