[webkit-changes] [WebKit/WebKit] f84b23: Don't fire a mousemove event when a modifier key i...

[Abrar Rahman Protyasha]

  Branch: refs/heads/main
  Home:   https://github.com/WebKit/WebKit
  Commit: f84b2332af6e577f2e2e3abcf8bc9768410c1f52
      https://github.com/WebKit/WebKit/commit/f84b2332af6e577f2e2e3abcf8bc9768410c1f52
  Author: Abrar Rahman Protyasha <a_protyasha at apple.com>
  Date:   2023-05-23 (Tue, 23 May 2023)

  Changed paths:
    A LayoutTests/fast/events/no-mousemove-on-modifier-key-press-expected.txt
    A LayoutTests/fast/events/no-mousemove-on-modifier-key-press.html
    M Source/WebCore/page/Chrome.cpp
    M Source/WebCore/page/Chrome.h
    M Source/WebCore/page/EventHandler.cpp
    M Source/WebCore/page/EventHandler.h
    M Source/WebKit/UIProcess/WebPageProxy.cpp
    M Source/WebKit/UIProcess/WebPageProxy.h
    M Source/WebKit/UIProcess/mac/WebViewImpl.h
    M Source/WebKit/UIProcess/mac/WebViewImpl.mm
    M Source/WebKit/WebProcess/WebPage/WebPage.cpp
    M Source/WebKit/WebProcess/WebPage/WebPage.h
    M Source/WebKit/WebProcess/WebPage/WebPage.messages.in

  Log Message:
  -----------
  Don't fire a mousemove event when a modifier key is pressed
https://bugs.webkit.org/show_bug.cgi?id=16271
rdar://81287778

Reviewed by Wenson Hsieh.

Previously, we dispatched mousemove events whenever a modifier key was
pressed. This was used to call the UIClient delegate callback
mouseDidMoveOverElement, which downstream clients could use to modify
various behaviors based on whether or not modifier keys were pressed.

Unfortunately, the act of dispatching a mousemove event meant that
pressing modifier keys could cause unexpected mouse behavior. One notable
example is Slack. When using Slack through Minibrowser, it is possible
to experience spontaneous mouse selection when a cursor was originally
placed behind a completion list, since our hover state gets constantly
re-evaluated.

In this patch, we introduce a mechanism to avoid the need to fire a
mousemove event when modifier keys are pressed. This is achieved by
adding a new message from the UI process to the web process where we
request that a given mouse event's hit test be performed. With the hit
test result and user data associated with said mouse event, we can
simply call into the UIClient delegate callback mouseDidMoveOverElement,
avoiding the regular mouse event dispatch dance altogether.

* LayoutTests/fast/events/no-mousemove-on-modifier-key-press-expected.txt: Added.
* LayoutTests/fast/events/no-mousemove-on-modifier-key-press.html: Added.

Layout test that verifies pressing the modifier keys does not fire a
MouseMove event.

* Source/WebCore/page/Chrome.h:

Export (and make public) Chrome::getToolTip to access from the web
process.

* Source/WebCore/page/EventHandler.cpp:
(WebCore::EventHandler::getHitTypeForMouseMoveEvent):
(WebCore::EventHandler::getHitTestResultForMouseEvent):
(WebCore::EventHandler::handleMouseMoveEvent):

Introduce two functions getHitTypeForMouseMoveEvent and
getHitTestResultForMouseEvent. The latter strips out some common code
from handleMouseMoveEvent so that it can be called independently to
identify a hitType, whereas the former is a handy way to produce a
hitTestResult without bringing the MouseEventWithHitTestResults type
into web process land.

* Source/WebCore/page/EventHandler.h:
* Source/WebKit/UIProcess/WebPageProxy.cpp:
(WebKit::WebPageProxy::dispatchMouseDidMoveOverElementAsynchronously):

Introduce a method that communicates the need for user data and a hit
test on a mouse event without actually dispatching said mouse event to
the web process. Once we round trip from the web process, it feeds the
returned data to the client delegate callback mouseDidMoveOverElement.

* Source/WebKit/UIProcess/WebPageProxy.h:
* Source/WebKit/UIProcess/mac/WebViewImpl.h:
* Source/WebKit/UIProcess/mac/WebViewImpl.mm:
(WebKit::WebViewImpl::viewDidMoveToWindow):
(WebKit::WebViewImpl::fireMouseDidMoveOverElement):
(WebKit::WebViewImpl::postFakeMouseMovedEventForFlagsChangedEvent): Deleted.

Rename postFakeMouseMovedEventForFlagsChangedEvent to
fireMouseDidMoveOverElement to better represent our signaling intent.

fireMouseDidMoveOverElement then communicates with the web page to
receive user data and hit test results before passing that over to the
client delegate callback.

* Source/WebKit/WebProcess/WebPage/WebPage.cpp:
(WebKit::WebPage::performHitTestAndGetUserData):
* Source/WebKit/WebProcess/WebPage/WebPage.h:
* Source/WebKit/WebProcess/WebPage/WebPage.messages.in:

Introduce a new message that receives a mouse event from the UI process
and calls into the page's event handler and chrome clients to perform a
hit test on the received mouse event. This allows us to circumvent the
usual dance with a dispatched mouse event while returning the user data
and hit test result associated with a mouse event.

Canonical link: https://commits.webkit.org/264455@main