Fixed MouseArea threshold with preventStealing

When preventStealing is true both keepMouseGrab() and
d->stealMouse are true. This in turn enable the dragging immediately
since the condition "keepMouseGrab() && d->stealMouse && !d->drag->active()"
is true.
Conversely when preventStealing is false the dragging is enabled in the
next move event since keepMouseGrab() and d->stealMouse are set true
inside the last "if" "!keepMouseGrab() && ...check threshold..".
This patch adds a new boolean flag for storing if we detected a drag motion
(so we exceeded the threshold) and enable the dragging iff this flag is true.
With this change:
- if preventStealing is true (and so keepMouseGrab() and d->stealMouse) the
additional d->overThresHold prevent the start of dragging. At the same time
the last if (!keepMouseGrab()) cannot be executed since keepMouseGrab is true
and we still check for the threshold being exceeded.
- if preventStealing is false, we still check for exceeding the threshold and
if this happen we enter in the last "if" since !keepMousegrab() && d->overThreshold
is true taking the mouseGrab as without this patch

Task-number: QTBUG-52534
Change-Id: I2b14d3048b6f8223c90ce5e2fd26e7ca706cb56a
Reviewed-by: Michael Brasser <michael.brasser@live.com>
Reviewed-by: Robin Burchell <robin.burchell@viroteck.net>
Reviewed-by: Shawn Rutledge <shawn.rutledge@theqtcompany.com>

1 files changed, 13 insertions, 8 deletions

diff --git a/src/quick/items/qquickmousearea.cpp b/src/quick/items/qquickmousearea.cpp
index ef053abbd1..d66e55aa12 100644
--- a/src/quick/items/qquickmousearea.cpp
+++ b/src/quick/items/qquickmousearea.cpp
@@ -52,7 +52,7 @@ DEFINE_BOOL_CONFIG_OPTION(qmlVisualTouchDebugging, QML_VISUAL_TOUCH_DEBUGGING)
 QQuickMouseAreaPrivate::QQuickMouseAreaPrivate()
 : enabled(true), scrollGestureEnabled(true), hovered(false), longPress(false),
   moved(false), stealMouse(false), doubleClick(false), preventStealing(false),
-  propagateComposedEvents(false), pressed(0)
+  propagateComposedEvents(false), overThreshold(false), pressed(0)
 #ifndef QT_NO_DRAGANDDROP
   , drag(0)
 #endif
@@ -715,7 +715,7 @@ void QQuickMouseArea::mouseMoveEvent(QMouseEvent *event)
             curLocalPos = event->windowPos();
         }
 
-        if (keepMouseGrab() && d->stealMouse && !d->drag->active())
+        if (keepMouseGrab() && d->stealMouse && d->overThreshold && !d->drag->active())
             d->drag->setActive(true);
 
         QPointF startPos = d->drag->target()->parentItem()
@@ -741,16 +741,19 @@ void QQuickMouseArea::mouseMoveEvent(QMouseEvent *event)
         if (d->drag->active())
             d->drag->target()->setPosition(dragPos);
 
-        if (!keepMouseGrab()
-                && (QQuickWindowPrivate::dragOverThreshold(dragPos.x() - startPos.x(), Qt::XAxis, event, d->drag->threshold())
-                || QQuickWindowPrivate::dragOverThreshold(dragPos.y() - startPos.y(), Qt::YAxis, event, d->drag->threshold()))) {
-            setKeepMouseGrab(true);
-            d->stealMouse = true;
-
+        if (!d->overThreshold && (QQuickWindowPrivate::dragOverThreshold(dragPos.x() - startPos.x(), Qt::XAxis, event, d->drag->threshold())
+                                  || QQuickWindowPrivate::dragOverThreshold(dragPos.y() - startPos.y(), Qt::YAxis, event, d->drag->threshold())))
+        {
+            d->overThreshold = true;
             if (d->drag->smoothed())
                 d->startScene = event->windowPos();
         }
 
+        if (!keepMouseGrab() && d->overThreshold) {
+            setKeepMouseGrab(true);
+            d->stealMouse = true;
+        }
+
         d->moved = true;
     }
 #endif
@@ -767,6 +770,7 @@ void QQuickMouseArea::mouseReleaseEvent(QMouseEvent *event)
 {
     Q_D(QQuickMouseArea);
     d->stealMouse = false;
+    d->overThreshold = false;
     if (!d->enabled && !d->pressed) {
         QQuickItem::mouseReleaseEvent(event);
     } else {
@@ -875,6 +879,7 @@ void QQuickMouseArea::ungrabMouse()
         d->pressed = 0;
         d->stealMouse = false;
         d->doubleClick = false;
+        d->overThreshold = false;
         setKeepMouseGrab(false);
 
 #ifndef QT_NO_DRAGANDDROP