QQuickWindow: Process a synthetic hover once per frame

This removes the limitation that hover only changes when the mouse moves, and
(in my opinion) is required to make hover functionality even remotely useful.
QtQuick scenes are a dynamic medium, items can move (or change) frequently, so
only changing this in response to a user action means it will frequently end up
out of date.

A very simple example of this is a ListView of delegates that each have a
background set on hover: when flicking the list, it won't reset the hover to
actually match the item under the mouse.

This is now not a (very) expensive operation to do, as deliverHoverEvent
does nothing if the item tree in question doesn't have hover enabled.

[ChangeLog][QtQuick][MouseArea] Hover state is now updated once per frame.
This means that MouseArea::containsMouse property will now be correct even
if the mouse is not moving, but items move under the cursor.  Likewise
the mouse position properties and positionChanged signal will act as if
the mouse had moved.

Task-number: QTBUG-40475
Task-number: QTBUG-42194
Task-number: QTBUG-33982
Task-number: QTBUG-42578
Task-number: QTBUG-52537
Change-Id: Ic2dcbb45339e11c07f5c6a9c95eb7f64957968eb
Reviewed-by: Gunnar Sletta <gunnar@sletta.org>
Reviewed-by: Robin Burchell <robin.burchell@viroteck.net>

1 files changed, 2 insertions, 3 deletions

diff --git a/src/quick/items/qquickmousearea.cpp b/src/quick/items/qquickmousearea.cpp
index 557922a861..66aff5c2f4 100644
--- a/src/quick/items/qquickmousearea.cpp
+++ b/src/quick/items/qquickmousearea.cpp
@@ -837,7 +837,7 @@ void QQuickMouseArea::hoverMoveEvent(QHoverEvent *event)
     Q_D(QQuickMouseArea);
     if (!d->enabled && !d->pressed) {
         QQuickItem::hoverMoveEvent(event);
-    } else {
+    } else if (d->lastPos != event->posF()) {
         d->lastPos = event->posF();
         d->lastModifiers = event->modifiers();
         QQuickMouseEvent &me = d->quickMouseEvent;
@@ -1083,8 +1083,7 @@ void QQuickMouseArea::setHoverEnabled(bool h)
     \qmlproperty bool QtQuick::MouseArea::containsMouse
     This property holds whether the mouse is currently inside the mouse area.
 
-    \warning This property is not updated if the area moves under the mouse: \e containsMouse will not change.
-    In addition, if hoverEnabled is false, containsMouse will only be valid
+    \warning If hoverEnabled is false, containsMouse will only be valid
     when the mouse is pressed while the mouse cursor is inside the MouseArea.
 */
 bool QQuickMouseArea::hovered() const