commit 2e3b642b317f8baf7d43546d085d09d93989f840
author timothy_horton@apple.com <timothy_horton@apple.com@268f45cc-cd09-0410-ab3c-d52691b4dbfc> Wed Jan 05 19:29:43 2022 +0000
committer timothy_horton@apple.com <timothy_horton@apple.com@268f45cc-cd09-0410-ab3c-d52691b4dbfc> Wed Jan 05 19:29:43 2022 +0000
tree 59a193c005318531e429fa6a1076401a5621edac
parent 99af18cc225de0b061ce27c2b7592b884f0301fe

Momentum Event Dispatcher: Momentum tails may get truncated if the duration runs longer than the system's
https://bugs.webkit.org/show_bug.cgi?id=234535
<rdar://problem/86338105>

Reviewed by Simon Fraser.

Source/WebKit:

Currently, synthetic momentum dispatch is strictly tied to the duration
of the real platform momentum phase, which has two unfortunate implications:

- if our phase runs shorter than the platform phase, we'll keep dispatching
  zero-delta events until the platform momentum ends

- more importantly, if our phase runs longer, it will be abruptly terminated
  when the platform momentum ends

In practice, our synthetic phase is very close in duration to the system one,
so the impact is minimal. But, to be safe, disentagle the two durations,
using a new bit from the platform to determine if the system momentum phase
was interrupted by the user (e.g. by tapping the trackpad) or naturally,
and ignoring the ended event in the natural case, allowing synthetic
events to continue being dispatched.

* Shared/WebWheelEvent.cpp:
(WebKit::WebWheelEvent::WebWheelEvent):
(WebKit::WebWheelEvent::encode const):
(WebKit::WebWheelEvent::decode):
* Shared/WebWheelEvent.h:
(WebKit::WebWheelEvent::momentumEndType const):
* Shared/WebWheelEventCoalescer.cpp:
(WebKit::WebWheelEventCoalescer::coalesce):
Plumb momentumEndType along on WebWheelEvent. Platforms that don't
provide information about the interruption reason will always say Unknown.

* Shared/mac/WebEventFactory.mm:
(WebKit::WebEventFactory::createWebWheelEvent):
Only bother looking up the CGEvent/IOHIDEvent once, and extract all
relevant details in one go.

* WebProcess/WebPage/MomentumEventDispatcher.cpp:
(WebKit::MomentumEventDispatcher::handleWheelEvent):
Don't interrupt the synthetic momentum phase if the momentum-ended event
comes from the natural end of the deceleration instead of an interruption
(or an unknown reason).

Keep track of whether we're in the middle of a platform momentum phase
that we chose (at momentum-begin time) to override. When deciding
whether to eat an incoming event, take *both* this new bit and whether
we are currently in the middle of a synthetic phase into account. It
is important to continue eating incoming events in the case where
the synthetic phase ended early (so `active` became false) but the
platform phase continues.

(WebKit::MomentumEventDispatcher::dispatchSyntheticMomentumEvent):
(WebKit::MomentumEventDispatcher::didEndMomentumPhase):
Adjust some logging wording to be more precise.

(WebKit::MomentumEventDispatcher::setScrollingAccelerationCurve):
Make this log public so that the curve value is visible in logs.

(WebKit::MomentumEventDispatcher::consumeDeltaForCurrentTime):
Make consumeDeltaForCurrentTime inform the client via an optional when
we are at the end of the delta table.

(WebKit::MomentumEventDispatcher::displayWasRefreshed):
Stop the synthetic momentum phase as soon as we run out of deltas.

(WebKit::MomentumEventDispatcher::computeNextDelta):
* WebProcess/WebPage/MomentumEventDispatcher.h:

Source/WTF:

* wtf/PlatformHave.h:
Add a HAVE for kIOHIDEventScrollMomentumInterrupted.


git-svn-id: http://svn.webkit.org/repository/webkit/trunk@287641 268f45cc-cd09-0410-ab3c-d52691b4dbfc