MouseArea: fix containsMouse behavior during visibility changes

QQuickItem returns whether it contains QGuiApplicationPrivate's
lastCursorPosition. Since that position stores the coordinate last seen
by Qt (the window border), it will always be within the window, and
within an item that covers that part of the window's border.

However, QQuickWindow stores the lastMousePosition as well, and resets
that value when it receives a QEvent::Leave. We can use that to test
whether the  window that contains the item has seen a Leave event, in
which case the item is definitely not under the mouse.

Notes on the test: That we use QPointF() as the "reset" value leave the
small possibility that the cursor might be at position 0,0 of the window
(ie inside the window), and the QQuickItem there will not be under the
mouse. We can't confirm this (through an expected failure test), as
QTest::mouseMove interprets a QPoint(0, 0) as "center of the window".

And since we can't simulate mouse moves outside a window's boundary
using QTest::mouseMove, the test needs to explicitly synthesize a
QEvent::Leave for the window.

Fixes: QTBUG-87197
Change-Id: I04870d6e914092275d9d790312fc702fb99f2935
Done-with: Ivan Solovev <ivan.solovev@qt.io>
Reviewed-by: Tor Arne Vestbø <tor.arne.vestbo@qt.io>
(cherry picked from commit ba1246c543118515ea244787f3d7f9c1133ccf0f)
Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>

1 files changed, 6 insertions, 0 deletions

diff --git a/src/quick/items/qquickitem.cpp b/src/quick/items/qquickitem.cpp
index 38e83e08ff..83964c4a3a 100644
--- a/src/quick/items/qquickitem.cpp
+++ b/src/quick/items/qquickitem.cpp
@@ -7415,6 +7415,12 @@ bool QQuickItem::isUnderMouse() const
     if (!d->window)
         return false;
 
+    // QQuickWindow handles QEvent::Leave to reset the lastMousePosition
+    // FIXME: Using QPointF() as the reset value means an item will not be
+    // under the mouse if the mouse is at 0,0 of the window.
+    if (QQuickWindowPrivate::get(d->window)->lastMousePosition == QPointF())
+        return false;
+
     QPointF cursorPos = QGuiApplicationPrivate::lastCursorPosition;
     return contains(mapFromScene(d->window->mapFromGlobal(cursorPos.toPoint())));
 }