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Bug 1875424 - Make PresShell::HandleEvent flush pending synthetic mouse move at handling eMouseMove r=smaug

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`mouse_boundary_events_after_removing_last_over_element.html` expects that
a `mouseover` should be fired between `click` and `mousemove`, but it's
dispatched by a synthetic mouse move event caused by removing the click target.
The fix of bug 1864654 tried to fix this kind of issues, but it does not flush
pending event at `eMouseMove`.  Therefore, the synthetic mouse move may not be
handled before handling `eMouseMove` which is caused by `pointerMove()` in the
test.

I guess that we need to make it flush before all events which are directly
caused by a user input.  However, I don't want to do it for now because of
the risk.

Depends on D199607

Differential Revision: https://phabricator.services.mozilla.com/D199694
This commit is contained in:
Masayuki Nakano
2024-01-26 15:05:37 +00:00
parent e1d0f5f421
commit fb67854d77
1 changed files with 10 additions and 2 deletions
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12
layout/base/PresShell.cpp
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@@ -6946,10 +6946,16 @@ nsresult PresShell::HandleEvent(nsIFrame* aFrameForPresShell,
if (mPresContext) {
switch (aGUIEvent->mMessage) {
case eMouseMove:
if (!aGUIEvent->AsMouseEvent()->IsReal()) {
break;
}
[[fallthrough]];
case eMouseDown:
case eMouseUp: {
// We should flush pending mousemove event before that because the event
// may occur without proper boundary event. E.g., if a mousedown event
// We should flush pending mousemove event now because some mouse
// boundary events which should've already been dispatched before a user
// input may have not been dispatched. E.g., if a mousedown event
// listener removed or appended an element under the cursor and mouseup
// event comes immediately after that, mouseover or mouseout may have
// not been dispatched on the new element yet.
@@ -6959,6 +6965,8 @@ nsresult PresShell::HandleEvent(nsIFrame* aFrameForPresShell,
// eMouseUp. That could cause unexpected behavior if a `mouseover`
// event listener assumes it's always disptached before `mousedown`.
// However, we're not sure whether it could happen with users' input.
// FIXME: Perhaps, we need to do this for all events which are directly
// caused by user input, e.g., eKeyDown, etc.
RefPtr<PresShell> rootPresShell =
mPresContext->IsRoot() ? this : GetRootPresShell();
if (rootPresShell && rootPresShell->mSynthMouseMoveEvent.IsPending()) {