macOS: Add QCocoaWindowManager for dealing with window levels

Moves and improves the logic for lowering splash screens to a dedicated
window manager, which will learn more tricks in patches to come.

Change-Id: I8b8fd1dd78fdaf6f106a59c84d2a59254f3539c3
Reviewed-by: Volker Hilsheimer <volker.hilsheimer@qt.io>
Reviewed-by: Timur Pocheptsov <timur.pocheptsov@qt.io>

src/plugins/platforms/cocoa/cocoa.pro

@@ -6,6 +6,7 @@ SOURCES += main.mm \
     qcocoatheme.mm \
     qcocoabackingstore.mm \
     qcocoawindow.mm \
+    qcocoawindowmanager.mm \
     qnsview.mm \
     qnswindow.mm \
     qnswindowdelegate.mm \
@@ -41,6 +42,7 @@ HEADERS += qcocoaintegration.h \
     qcocoatheme.h \
     qcocoabackingstore.h \
     qcocoawindow.h \
+    qcocoawindowmanager.h \
     qnsview.h \
     qnswindow.h \
     qnswindowdelegate.h \

src/plugins/platforms/cocoa/qcocoaintegration.mm

@@ -217,25 +217,6 @@ QCocoaIntegration::QCocoaIntegration(const QStringList &paramList)
 
     connect(qGuiApp, &QGuiApplication::focusWindowChanged,
         this, &QCocoaIntegration::focusWindowChanged);
-
-    static auto splashScreenHider = QMacKeyValueObserver(NSApp, @"modalWindow", []{
-        const QWindowList allWindows = QGuiApplication::topLevelWindows();
-        for (QWindow *window : allWindows) {
-            if ((window->flags() & Qt::SplashScreen) == Qt::SplashScreen) {
-                QCocoaWindow *platformWindow = static_cast<QCocoaWindow*>(window->handle());
-                NSWindow *splashWindow = platformWindow->view().window;
-                if (!splashWindow)
-                    continue;
-                if (NSApp.modalWindow) {
-                    NSInteger originalLevel = splashWindow.level;
-                    splashWindow.level = NSNormalWindowLevel;
-                    window->setProperty("_q_levelBeforeModalSession", (qlonglong)originalLevel);
-                } else if (NSInteger originalLevel = window->property("_q_levelBeforeModalSession").toLongLong()) {
-                    splashWindow.level = originalLevel;
-                }
-            }
-        }
-    });
 }
 
 QCocoaIntegration::~QCocoaIntegration()

src/plugins/platforms/cocoa/qcocoawindowmanager.h

@@ -0,0 +1,63 @@
+/****************************************************************************
+**
+** Copyright (C) 2019 The Qt Company Ltd.
+** Contact: https://www.qt.io/licensing/
+**
+** This file is part of the plugins of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:LGPL$
+** Commercial License Usage
+** Licensees holding valid commercial Qt licenses may use this file in
+** accordance with the commercial license agreement provided with the
+** Software or, alternatively, in accordance with the terms contained in
+** a written agreement between you and The Qt Company. For licensing terms
+** and conditions see https://www.qt.io/terms-conditions. For further
+** information use the contact form at https://www.qt.io/contact-us.
+**
+** GNU Lesser General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU Lesser
+** General Public License version 3 as published by the Free Software
+** Foundation and appearing in the file LICENSE.LGPL3 included in the
+** packaging of this file. Please review the following information to
+** ensure the GNU Lesser General Public License version 3 requirements
+** will be met: https://www.gnu.org/licenses/lgpl-3.0.html.
+**
+** GNU General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU
+** General Public License version 2.0 or (at your option) the GNU General
+** Public license version 3 or any later version approved by the KDE Free
+** Qt Foundation. The licenses are as published by the Free Software
+** Foundation and appearing in the file LICENSE.GPL2 and LICENSE.GPL3
+** included in the packaging of this file. Please review the following
+** information to ensure the GNU General Public License requirements will
+** be met: https://www.gnu.org/licenses/gpl-2.0.html and
+** https://www.gnu.org/licenses/gpl-3.0.html.
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+#ifndef QCOCOAWINDOWMANAGER_H
+#define QCOCOAWINDOWMANAGER_H
+
+#include <QtCore/qglobal.h>
+
+#include <AppKit/AppKit.h>
+
+QT_BEGIN_NAMESPACE
+
+class QCocoaWindowManager
+{
+public:
+    static QCocoaWindowManager *instance();
+
+private:
+    QCocoaWindowManager();
+    void initialize();
+
+    void modalSessionChanged();
+};
+
+QT_END_NAMESPACE
+
+#endif // QCOCOAWINDOWMANAGER_H

src/plugins/platforms/cocoa/qcocoawindowmanager.mm

@@ -0,0 +1,108 @@
+/****************************************************************************
+**
+** Copyright (C) 2019 The Qt Company Ltd.
+** Contact: https://www.qt.io/licensing/
+**
+** This file is part of the plugins of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:LGPL$
+** Commercial License Usage
+** Licensees holding valid commercial Qt licenses may use this file in
+** accordance with the commercial license agreement provided with the
+** Software or, alternatively, in accordance with the terms contained in
+** a written agreement between you and The Qt Company. For licensing terms
+** and conditions see https://www.qt.io/terms-conditions. For further
+** information use the contact form at https://www.qt.io/contact-us.
+**
+** GNU Lesser General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU Lesser
+** General Public License version 3 as published by the Free Software
+** Foundation and appearing in the file LICENSE.LGPL3 included in the
+** packaging of this file. Please review the following information to
+** ensure the GNU Lesser General Public License version 3 requirements
+** will be met: https://www.gnu.org/licenses/lgpl-3.0.html.
+**
+** GNU General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU
+** General Public License version 2.0 or (at your option) the GNU General
+** Public license version 3 or any later version approved by the KDE Free
+** Qt Foundation. The licenses are as published by the Free Software
+** Foundation and appearing in the file LICENSE.GPL2 and LICENSE.GPL3
+** included in the packaging of this file. Please review the following
+** information to ensure the GNU General Public License requirements will
+** be met: https://www.gnu.org/licenses/gpl-2.0.html and
+** https://www.gnu.org/licenses/gpl-3.0.html.
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+#include "qcocoawindowmanager.h"
+#include "qcocoawindow.h"
+
+#include <QtCore/private/qcore_mac_p.h>
+
+#include <QtGui/qguiapplication.h>
+#include <QtGui/qwindow.h>
+
+QT_BEGIN_NAMESPACE
+
+QCocoaWindowManager *QCocoaWindowManager::instance()
+{
+    static auto *instance = new QCocoaWindowManager;
+    return instance;
+}
+
+QCocoaWindowManager::QCocoaWindowManager()
+{
+    if (NSApp) {
+        initialize();
+    } else {
+        static auto applicationDidFinishLaunching(QMacNotificationObserver(nil,
+            NSApplicationDidFinishLaunchingNotification, [this] { initialize(); }));
+    }
+}
+
+void QCocoaWindowManager::initialize()
+{
+    Q_ASSERT(NSApp);
+
+    // Whenever the modalWindow property of NSApplication changes we have a new
+    // modal session running. Observing the app modal window instead of our own
+    // event dispatcher sessions allows us to track session started by native
+    // APIs as well. We need to check the initial state as well, in case there
+    // is already a modal session running.
+    static auto modalSessionObserver(QMacKeyValueObserver(
+        NSApp, @"modalWindow", [this] { modalSessionChanged(); },
+        NSKeyValueObservingOptionInitial | NSKeyValueObservingOptionNew));
+}
+
+void QCocoaWindowManager::modalSessionChanged()
+{
+    // Make sure that no window is overlapping the modal window. This can
+    // happen for e.g. splash screens, which have the NSPopUpMenuWindowLevel.
+    for (auto *window : QGuiApplication::topLevelWindows()) {
+        auto *platformWindow = static_cast<QCocoaWindow*>(window->handle());
+        if (!platformWindow)
+            continue;
+
+        auto naturalWindowLevel = platformWindow->windowLevel(window->flags());
+        if (naturalWindowLevel > NSModalPanelWindowLevel) {
+            NSWindow *nativeWindow = platformWindow->nativeWindow();
+            if (NSApp.modalWindow) {
+                // Lower window to that of the modal windows, but no less
+                nativeWindow.level = NSModalPanelWindowLevel;
+                [nativeWindow orderBack:nil];
+            } else {
+                // Restore window's natural window level, whatever that was
+                nativeWindow.level = naturalWindowLevel;
+            }
+        }
+    }
+}
+
+static void initializeWindowManager() { Q_UNUSED(QCocoaWindowManager::instance()); }
+Q_CONSTRUCTOR_FUNCTION(initializeWindowManager)
+
+QT_END_NAMESPACE
+