Cocoa: Correct enter/leave event handling.

Make top-level windows generate enter/leave events
for sub-windows. Keep track of the current "under mouse"
window in mouseMoved and send EnterLeave events when
it changes.

mouseEntered/mouseExited handles enters and leaves
from the top-level window.

Add tests/manual/cocoa/nativewidgets.

Task-number: QTBUG-27550
Task-number: QTBUG-29751

Change-Id: If4b9f9e0f39d9fb05fdab45a100ffdcf107965ad
Reviewed-by: Gabriel de Dietrich <gabriel.dedietrich@digia.com>

3 files changed, 57 insertions, 4 deletions

diff --git a/src/plugins/platforms/cocoa/qcocoawindow.h b/src/plugins/platforms/cocoa/qcocoawindow.h
index c19017166b..5029321247 100644
--- a/src/plugins/platforms/cocoa/qcocoawindow.h
+++ b/src/plugins/platforms/cocoa/qcocoawindow.h
@@ -150,6 +150,7 @@ public:
     qreal devicePixelRatio() const;
     void exposeWindow();
     void obscureWindow();
+    QWindow *childWindowAt(QPoint windowPoint);
 protected:
     // NSWindow handling. The QCocoaWindow/QNSView can either be displayed
     // in an existing NSWindow or in one created by Qt.
@@ -177,6 +178,7 @@ public: // for QNSView
     Qt::WindowState m_synchedWindowState;
     Qt::WindowModality m_windowModality;
     QPointer<QWindow> m_activePopupWindow;
+    QPointer<QWindow> m_underMouseWindow;
 
     bool m_inConstructor;
     QCocoaGLContext *m_glContext;
diff --git a/src/plugins/platforms/cocoa/qcocoawindow.mm b/src/plugins/platforms/cocoa/qcocoawindow.mm
index a7e75480ea..9988cea597 100644
--- a/src/plugins/platforms/cocoa/qcocoawindow.mm
+++ b/src/plugins/platforms/cocoa/qcocoawindow.mm
@@ -927,6 +927,21 @@ void QCocoaWindow::obscureWindow()
     }
 }
 
+QWindow *QCocoaWindow::childWindowAt(QPoint windowPoint)
+{
+    QWindow *targetWindow = window();
+    foreach (QObject *child, targetWindow->children()) {
+        if (QWindow *childWindow = qobject_cast<QWindow *>(child)) {
+            if (childWindow->geometry().contains(windowPoint)) {
+                QCocoaWindow* platformWindow = static_cast<QCocoaWindow*>(childWindow->handle());
+                targetWindow = platformWindow->childWindowAt(windowPoint - childWindow->position());
+            }
+        }
+    }
+
+    return targetWindow;
+}
+
 QMargins QCocoaWindow::frameMargins() const
 {
     NSRect frameW = [m_nsWindow frame];
diff --git a/src/plugins/platforms/cocoa/qnsview.mm b/src/plugins/platforms/cocoa/qnsview.mm
index 12a6bb9e69..3046b898df 100644
--- a/src/plugins/platforms/cocoa/qnsview.mm
+++ b/src/plugins/platforms/cocoa/qnsview.mm
@@ -599,6 +599,7 @@ static QTouchDevice *touchDevice = 0;
     if (NSIsEmptyRect([self visibleRect]))
         return;
 
+    // Remove current trakcing areas:
     QCocoaAutoReleasePool pool;
     if (NSArray *trackingArray = [self trackingAreas]) {
         NSUInteger size = [trackingArray count];
@@ -611,7 +612,7 @@ static QTouchDevice *touchDevice = 0;
     // Ideally, we shouldn't have NSTrackingMouseMoved events included below, it should
     // only be turned on if mouseTracking, hover is on or a tool tip is set.
     // Unfortunately, Qt will send "tooltip" events on mouse moves, so we need to
-    // turn it on in ALL case. That means EVERY QCocoaView gets to pay the cost of
+    // turn it on in ALL case. That means EVERY QWindow gets to pay the cost of
     // mouse moves delivered to it (Apple recommends keeping it OFF because there
     // is a performance hit). So it goes.
     NSUInteger trackingOptions = NSTrackingMouseEnteredAndExited | NSTrackingActiveInActiveApp
@@ -628,23 +629,58 @@ static QTouchDevice *touchDevice = 0;
 {
     if (m_window->flags() & Qt::WindowTransparentForInput)
         return [super mouseMoved:theEvent];
-    [self handleMouseEvent:theEvent];
+
+    QPoint windowPoint, screenPoint;
+    [self convertFromEvent:theEvent toWindowPoint:&windowPoint andScreenPoint:&screenPoint];
+    QWindow *childWindow = m_platformWindow->childWindowAt(windowPoint);
+
+    // Top-level windows generate enter-leave events for sub-windows.
+    // Qt wants to know which window (if any) will be entered at the
+    // the time of the leave. This is dificult to accomplish by
+    // handling mouseEnter and mouseLeave envents, since they are sent
+    // individually to different views.
+    if (m_platformWindow->m_nsWindow && childWindow) {
+        if (childWindow != m_platformWindow->m_underMouseWindow) {
+            QWindowSystemInterface::handleEnterLeaveEvent(childWindow, m_platformWindow->m_underMouseWindow, windowPoint, screenPoint);
+            m_platformWindow->m_underMouseWindow = childWindow;
+        }
+    }
+
+    // Cocoa keeps firing mouse move events for obscured parent views. Qt should not
+    // send those events so filter them out here.
+    if (childWindow != m_window)
+        return;
+
+    [self handleMouseEvent: theEvent];
 }
 
 - (void)mouseEntered:(NSEvent *)theEvent
 {
     if (m_window->flags() & Qt::WindowTransparentForInput)
         return [super mouseEntered:theEvent];
+
+    // Top-level windows generate enter events for sub-windows.
+    if (!m_platformWindow->m_nsWindow)
+        return;
+
     QPoint windowPoint, screenPoint;
     [self convertFromEvent:theEvent toWindowPoint:&windowPoint andScreenPoint:&screenPoint];
-    QWindowSystemInterface::handleEnterEvent(m_window, windowPoint, screenPoint);
+    m_platformWindow->m_underMouseWindow = m_platformWindow->childWindowAt(windowPoint);
+    QWindowSystemInterface::handleEnterEvent(m_platformWindow->m_underMouseWindow, windowPoint, screenPoint);
 }
 
 - (void)mouseExited:(NSEvent *)theEvent
 {
     if (m_window->flags() & Qt::WindowTransparentForInput)
         return [super mouseExited:theEvent];
-    QWindowSystemInterface::handleLeaveEvent(m_window);
+    Q_UNUSED(theEvent);
+
+    // Top-level windows generate leave events for sub-windows.
+    if (!m_platformWindow->m_nsWindow)
+        return;
+
+    QWindowSystemInterface::handleLeaveEvent(m_platformWindow->m_underMouseWindow);
+    m_platformWindow->m_underMouseWindow = 0;
 }
 
 - (void)rightMouseDown:(NSEvent *)theEvent