tree 5e4d950fe8bb8ba08f27090ac72d9fcfc32ef324
parent 1dbf9eaa372c3e11d9ea18860d42ae1168228aeb
author dbates@webkit.org <dbates@webkit.org@268f45cc-cd09-0410-ab3c-d52691b4dbfc> 1563223243 +0000
committer dbates@webkit.org <dbates@webkit.org@268f45cc-cd09-0410-ab3c-d52691b4dbfc> 1563223243 +0000

Typing into a cell in a Google Sheet lags behind by one character
https://bugs.webkit.org/show_bug.cgi?id=199587
<rdar://problem/51616845>

Reviewed by Brent Fulgham.

Source/WebCore:

Add a Google Sheets quirk. Put all DOM timers scheduled from keydown and keypress event listeners
into a holding tank. The timers continue to tick, but are barred from executing their action until
the next text insertion or deletion or 32 ms (on device) have elapsed, whichever is sooner. We only
allocate a holding tank once per document, only if the quirk is active, and this allocation is done
when the document schedules a timer on keydown or keypress. The holding tank lives for the lifetime
of the document.

The story behind the quirk:

On keypress Google Sheets schedules timers and expects that a DOM update will occur (i.e. text
will be inserted or deleted) within the same event loop iteration as the dispatched keypress. The
UI Events spec. [1] makes no such guarantee of when a DOM update must occur in relation to the keypress
event. It could happen in the same event loop iteration as the key press (as Google expects), the
next iteration, 500ms later, 2 minutes later, etc. What the spec does guarantee is that by the time
a DOM input event is dispatched that the DOM will be updated. And this is the solution to the problem
Google Sheets is trying to solve, but is doing so using pre-IE 9 technology (though similar
functionality was available via onpropertychange in IE < 9).

See also <https://github.com/w3c/uievents/issues/238>, which is tracking a spec. text update for
this quirk.

Test: fast/events/ios/dom-update-on-keydown-quirk.html

[1] <https://w3c.github.io/uievents/> (Editor's Draft, 14 October 2018)

* SourcesCocoa.txt:
* WebCore.xcodeproj/project.pbxproj:
Add some files to the project.

* dom/Document.cpp:
(WebCore::Document::domTimerHoldingTank): Added.
* dom/Document.h:
(WebCore::Document::domTimerHoldingTankIfExists): Added.

* page/DOMTimer.cpp:
(WebCore::DOMTimer::install): Put the newly instantiated timer into the holding tank.
(WebCore::DOMTimer::removeById): Remove the timer from the holding tank.
(WebCore::DOMTimer::fired): Check if the timer is in the holding tank. If it is and it is a one-
shot timer then schedule it for the next event loop iteration. If it's a repeating timer just
let it continue ticking. Otherwise, do what we no now and execute the timer's action. The reason
we do not suspend timers in the holding tank is because:
    1. Far out timers (Google Sheets registers timers as far out as 5 minutes!) are not penalized.
    Though smart supension logic could avoid this. See (3).

    2. Empirical observations indicate that the keyboard will perform the insertion or deletion
    reasonably quickly (not the same event loop iteration as the keydown, but within two iterations out).
    So, the timers in the holding tank are short-lived.

    3. Simplifies the code. There is no need to keep additional bookkeeping to track multiple timer
    suspension reasons (timers currently can only have one suspension reason) or alternatively defer
    scheduling a timer until a later time and computing a new "fair" firing time when scheduled.
* page/EventHandler.cpp:
(WebCore::EventHandler::internalKeyEvent): Place a token on the stack to put all DOM timers
scheduled on keydown and keypress into the holding tank if the quirk is enabled.
* page/Quirks.cpp:
(WebCore::Quirks::needsDeferKeyDownAndKeyPressTimersUntilNextEditingCommand const): Added.
* page/Quirks.h:
* page/Settings.yaml: Added setting so that this quirk can be enabled from a layout test. This setting
also lets us enable the quirk for all sites or for certain third-party apps if desired.
* page/ios/DOMTimerHoldingTank.cpp: Added.
(WebCore::DOMTimerHoldingTank::DOMTimerHoldingTank):
(WebCore::DOMTimerHoldingTank::add):
(WebCore::DOMTimerHoldingTank::remove):
(WebCore::DOMTimerHoldingTank::contains):
(WebCore::DOMTimerHoldingTank::removeAll):
(WebCore::DOMTimerHoldingTank::stopExceededMaximumHoldTimer):
* page/ios/DOMTimerHoldingTank.h: Added.
(WebCore::DeferDOMTimersForScope::DeferDOMTimersForScope):
(WebCore::DeferDOMTimersForScope::~DeferDOMTimersForScope):
(WebCore::DeferDOMTimersForScope::isDeferring):

Source/WebKit:

Remove all timers from the holding tank on text insertion or deletion (represented as an
editing command). Timers that were in the holding tank never stopped ticking and will now
be able to execute their action.

* WebProcess/WebPage/WebPage.cpp:
(WebKit::WebPage::executeEditingCommand):
(WebKit::WebPage::insertTextAsync):
(WebKit::WebPage::setCompositionAsync):
(WebKit::WebPage::confirmCompositionAsync):
Call platformWillPerformEditingCommand().

* WebProcess/WebPage/WebPage.h:
(WebKit::WebPage::platformWillPerformEditingCommand): Added.
* WebProcess/WebPage/ios/WebPageIOS.mm:
(WebKit::WebPage::platformWillPerformEditingCommand): Remove all the timers from the holding
tank if we have a holding tank.

LayoutTests:

Add a test that enables the quirk and ensures that the DOM is up-to-date on expiration of a
zero timer scheduled from keydown, keypress, keyup, and input.

* fast/events/ios/dom-update-on-keydown-quirk-expected.txt: Added.
* fast/events/ios/dom-update-on-keydown-quirk.html: Added.

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@247444 268f45cc-cd09-0410-ab3c-d52691b4dbfc