Cocoa: Make QScreen::topLevelAt() work correctly

The QPlatformScreen::topLevelAt() default implementation
is flawed in that it does not check z-ordering but
simply returns the first window in the window list
that contains the test point.

Add QCocoaScreen::topLevelAt(). Use [NSApp orderedWindows]
to iterate through the window list in z order. Add
a NSWindow->QCococaWindow mapping hash to QCocoaIntegration
for getting the corresponding QWindow once a NSWindow
is found.

Task-number: QTBUG-37597
Change-Id: I7af70163a32528cb56f8d6caa037b98f580ee191
Reviewed-by: Gabriel de Dietrich <gabriel.dedietrich@digia.com>

src/plugins/platforms/cocoa/qcocoaintegration.h

@@ -80,6 +80,7 @@ public:
     qreal refreshRate() const { return m_refreshRate; }
     QString name() const { return m_name; }
     QPlatformCursor *cursor() const  { return m_cursor; }
+    QWindow *topLevelAt(const QPoint &point) const;
     QList<QPlatformScreen *> virtualSiblings() const { return m_siblings; }
 
     // ----------------------------------------------------
@@ -138,6 +139,8 @@ public:
     void setToolbar(QWindow *window, NSToolbar *toolbar);
     NSToolbar *toolbar(QWindow *window) const;
     void clearToolbars();
+    void setWindow(NSWindow* nsWindow, QCocoaWindow *window);
+    QCocoaWindow *window(NSWindow *window);
 private:
     static QCocoaIntegration *mInstance;
 
@@ -156,6 +159,7 @@ private:
     QScopedPointer<QCocoaKeyMapper> mKeyboardMapper;
 
     QHash<QWindow *, NSToolbar *> mToolbars;
+    QHash<NSWindow *, QCocoaWindow*> mWindows;
 };
 
 QT_END_NAMESPACE

src/plugins/platforms/cocoa/qcocoaintegration.mm

@@ -156,6 +156,24 @@ qreal QCocoaScreen::devicePixelRatio() const
     }
 }
 
+QWindow *QCocoaScreen::topLevelAt(const QPoint &point) const
+{
+    // Get a z-ordered list of windows. Iterate through it until
+    // we find a window which contains the point.
+    for (NSWindow *nsWindow in [NSApp orderedWindows]) {
+        QCocoaWindow *cocoaWindow = QCocoaIntegration::instance()->window(nsWindow);
+        if (!cocoaWindow)
+            continue;
+        QWindow *window = cocoaWindow->window();
+        if (!window->isTopLevel())
+             continue;
+        if (window->geometry().contains(point))
+            return window;
+    }
+
+    return QPlatformScreen::topLevelAt(point);
+}
+
 extern CGContextRef qt_mac_cg_context(const QPaintDevice *pdev);
 
 QPixmap QCocoaScreen::grabWindow(WId window, int x, int y, int width, int height) const
@@ -500,6 +518,16 @@ NSToolbar *QCocoaIntegration::toolbar(QWindow *window) const
     return mToolbars.value(window);
 }
 
+void QCocoaIntegration::setWindow(NSWindow* nsWindow, QCocoaWindow *window)
+{
+    mWindows.insert(nsWindow, window);
+}
+
+QCocoaWindow *QCocoaIntegration::window(NSWindow *window)
+{
+    return mWindows.value(window);
+}
+
 void QCocoaIntegration::clearToolbars()
 {
     QHash<QWindow *, NSToolbar *>::const_iterator it = mToolbars.constBegin();

src/plugins/platforms/cocoa/qcocoawindow.mm

@@ -261,6 +261,8 @@ static bool isMouseEvent(NSEvent *ev)
 {
     [self close];
 
+    QCocoaIntegration::instance()->setWindow(self, 0);
+
     if (self.helper.grabbingMouse) {
         self.helper.releaseOnMouseUp = YES;
     } else {
@@ -327,6 +329,7 @@ static bool isMouseEvent(NSEvent *ev)
 {
     [self.helper detachFromPlatformWindow];
     [self close];
+    QCocoaIntegration::instance()->setWindow(self, 0);
     [self release];
 }
 
@@ -1402,6 +1405,8 @@ QCocoaNSWindow * QCocoaWindow::createNSWindow()
 
     applyContentBorderThickness(createdWindow);
 
+    QCocoaIntegration::instance()->setWindow(createdWindow, this);
+
     return createdWindow;
 }