QQuickWindow flushFrameSynchronousEvents: don't hover if nothing dirty

An optimization revising 6f84a09dfbd15aac023580cf06e7b8c24f3b524c
Calling hoverMoveEvent every frame is too inefficient when an item
subclass is actually doing something there.  For example, any
QtQuick-based Wayland compositor needs to notify its client windows
when hover state changes, so calling this method too often would
impose extra work to double-check whether it really changed or not.

Change-Id: I98b40a2083700e7a50820bd13154247444249e59
Reviewed-by: Robin Burchell <robin.burchell@viroteck.net>

1 files changed, 3 insertions, 2 deletions

diff --git a/src/quick/items/qquickwindow.cpp b/src/quick/items/qquickwindow.cpp
index 155a52bd9b..a58912e38f 100644
--- a/src/quick/items/qquickwindow.cpp
+++ b/src/quick/items/qquickwindow.cpp
@@ -2081,11 +2081,12 @@ void QQuickWindowPrivate::flushFrameSynchronousEvents()
             ut->startAnimations();
     }
 
-    // Once per frame, send a synthetic hover, in case items have changed position.
+    // Once per frame, if any items are dirty, send a synthetic hover,
+    // in case items have changed position, visibility, etc.
     // For instance, during animation (including the case of a ListView
     // whose delegates contain MouseAreas), a MouseArea needs to know
     // whether it has moved into a position where it is now under the cursor.
-    if (!q->mouseGrabberItem() && !lastMousePosition.isNull()) {
+    if (!q->mouseGrabberItem() && !lastMousePosition.isNull() && dirtyItemList) {
         bool accepted = false;
         bool delivered = deliverHoverEvent(contentItem, lastMousePosition, lastMousePosition, QGuiApplication::keyboardModifiers(), 0, accepted);
         if (!delivered)