Remove usages of deprecated APIs of QDesktopWidget

- Replaced the usages of the following deprecated APIs:
  * QDesktopWidget::screenCount() -> QGuiApplication::screens().size()
  * QDesktopWidget::screenGeometry(int) -> QGuiApplication::screens().at()
  * QDesktopWidget::screenNumber(QPoint) -> QGuiApplication::screenAt(QPoint)

- Added notes for the QWidget *QDesktopWidget::screen(int), which
currently has no replacement.

- Fixed the tests to build conditionally, only when these APIs are
enabled.

Task-number: QTBUG-76491
Change-Id: I2fdec96d0a6a4fc782c53549b05a5556412b8305
Reviewed-by: Volker Hilsheimer <volker.hilsheimer@qt.io>

src/widgets/kernel/qdesktopwidget.cpp

@@ -211,7 +211,9 @@ QDesktopWidget::QDesktopWidget()
     setObjectName(QLatin1String("desktop"));
     d->_q_updateScreens();
     connect(qApp, SIGNAL(screenAdded(QScreen*)), this, SLOT(_q_updateScreens()));
+#if QT_DEPRECATED_SINCE(5, 11)
     connect(qApp, SIGNAL(primaryScreenChanged(QScreen*)), this, SIGNAL(primaryScreenChanged()));
+#endif
 }
 
 QDesktopWidget::~QDesktopWidget()

src/widgets/widgets/qeffects.cpp

@@ -99,7 +99,7 @@ static QAlphaWidget* q_blend = 0;
   Constructs a QAlphaWidget.
 */
 QT_WARNING_PUSH
-QT_WARNING_DISABLE_DEPRECATED // QDesktopWidget::screen()
+QT_WARNING_DISABLE_DEPRECATED // ### Qt 6: Find a replacement for QDesktopWidget::screen()
 QAlphaWidget::QAlphaWidget(QWidget* w, Qt::WindowFlags f)
     : QWidget(QApplication::desktop()->screen(QDesktopWidgetPrivate::screenNumber(w)), f)
 {

tests/auto/widgets/kernel/qdesktopwidget/tst_qdesktopwidget.cpp

@@ -42,10 +42,12 @@ class tst_QDesktopWidget : public QObject
 private slots:
     void cleanup();
 
+#if QT_DEPRECATED_SINCE(5, 11)
     void numScreens();
     void primaryScreen();
-    void screenNumberForQWidget();
     void screenNumberForQPoint();
+#endif
+    void screenNumberForQWidget();
     void availableGeometry();
     void screenGeometry();
     void topLevels();
@@ -56,6 +58,7 @@ void tst_QDesktopWidget::cleanup()
     QVERIFY(QApplication::topLevelWidgets().isEmpty());
 }
 
+#if QT_DEPRECATED_SINCE(5, 11)
 void tst_QDesktopWidget::numScreens()
 {
     QDesktopWidget desktop;
@@ -68,14 +71,17 @@ void tst_QDesktopWidget::primaryScreen()
     QVERIFY(desktop.primaryScreen() >= 0);
     QVERIFY(desktop.primaryScreen() < desktop.numScreens());
 }
+#endif
 
 void tst_QDesktopWidget::availableGeometry()
 {
     QDesktopWidget desktop;
     QTest::ignoreMessage(QtWarningMsg, "QDesktopWidget::availableGeometry(): Attempt "
                                        "to get the available geometry of a null widget");
-    desktop.availableGeometry((QWidget *)0);
+    QRect r = desktop.availableGeometry(nullptr);
+    QVERIFY(r.isNull());
 
+#if QT_DEPRECATED_SINCE(5, 11)
     QRect total;
     QRect available;
 
@@ -90,13 +96,14 @@ void tst_QDesktopWidget::availableGeometry()
     QVERIFY(total.contains(available));
     QCOMPARE(desktop.availableGeometry(desktop.primaryScreen()), available);
     QCOMPARE(desktop.screenGeometry(desktop.primaryScreen()), total);
+#endif
 }
 
 void tst_QDesktopWidget::screenNumberForQWidget()
 {
     QDesktopWidget desktop;
 
-    QCOMPARE(desktop.screenNumber(0), 0);
+    QCOMPARE(desktop.screenNumber(nullptr), 0);
 
     QWidget widget;
     widget.show();
@@ -105,9 +112,10 @@ void tst_QDesktopWidget::screenNumberForQWidget()
 
     int widgetScreen = desktop.screenNumber(&widget);
     QVERIFY(widgetScreen > -1);
-    QVERIFY(widgetScreen < desktop.numScreens());
+    QVERIFY(widgetScreen < QGuiApplication::screens().size());
 }
 
+#if QT_DEPRECATED_SINCE(5, 11)
 void tst_QDesktopWidget::screenNumberForQPoint()
 {
     // make sure QDesktopWidget::screenNumber(QPoint) returns the correct screen
@@ -131,25 +139,28 @@ void tst_QDesktopWidget::screenNumberForQPoint()
     screen = desktopWidget->screenNumber(allScreens.bottomRight() + QPoint(1, 1));
     QVERIFY(screen >= 0 && screen < desktopWidget->numScreens());
 }
+#endif
 
 void tst_QDesktopWidget::screenGeometry()
 {
     QDesktopWidget *desktopWidget = QApplication::desktop();
     QTest::ignoreMessage(QtWarningMsg, "QDesktopWidget::screenGeometry(): Attempt "
                                        "to get the screen geometry of a null widget");
-    QRect r = desktopWidget->screenGeometry((QWidget *)0);
+    QRect r = desktopWidget->screenGeometry(nullptr);
     QVERIFY(r.isNull());
     QWidget widget;
     widget.show();
     QVERIFY(QTest::qWaitForWindowExposed(&widget));
     r = desktopWidget->screenGeometry(&widget);
 
+#if QT_DEPRECATED_SINCE(5, 11)
     QRect total;
     QRect available;
     for (int i = 0; i < desktopWidget->screenCount(); ++i) {
         total = desktopWidget->screenGeometry(i);
         available = desktopWidget->availableGeometry(i);
     }
+#endif
 }
 
 void tst_QDesktopWidget::topLevels()

tests/manual/qcursor/qcursorhighdpi/main.cpp

@@ -356,15 +356,12 @@ int main(int argc, char *argv[])
     QApplication app(argc, argv);
 
     MainWindowPtrList windows;
-
-    QDesktopWidget *desktopWidget = app.desktop();
-
     const int lastScreen = arguments.contains("-p")
         ? 0  // Primary screen only
-        : desktopWidget->screenCount() - 1; // All screens
+        : QGuiApplication::screens().size() - 1; // All screens
     for (int s = lastScreen; s >= 0; --s) {
-        MainWindowPtr window(new MainWindow(desktopWidget->screen(s)));
+        MainWindowPtr window(new MainWindow());
-        const QPoint pos = desktopWidget->screenGeometry(s).center() - QPoint(200, 100);
+        const QPoint pos = QGuiApplication::screens().at(s)->geometry().center() - QPoint(200, 100);
         window->move(pos);
         windows.append(window);
         window->show();

tests/manual/qdesktopwidget/main.cpp

@@ -34,6 +34,7 @@
 
 class DesktopView : public QGraphicsView
 {
+#if QT_DEPRECATED_SINCE(5, 11)
     Q_OBJECT
 public:
     DesktopView()
@@ -195,6 +196,7 @@ private:
     QGraphicsScene *scene;
     QGraphicsRectItem *that;
     QPoint thatRoot;
+#endif
 };
 
 #include "main.moc"

tests/manual/qscreen/main.cpp

@@ -61,8 +61,10 @@ public:
                 QLatin1String("Left-click to test QGuiApplication::topLevelAt(click pos)\nRight-click to ungrab\n") :
                 QLatin1String("Left-click to grab mouse\n");
         if (!m_cursorPos.isNull()) {
+            const auto screen = QGuiApplication::screenAt(m_cursorPos);
+            const auto screenNum = screen ? QGuiApplication::screens().indexOf(screen) : 0;
             txt += QString(QLatin1String("Current mouse position: %1, %2 on screen %3\n"))
-                    .arg(m_cursorPos.x()).arg(m_cursorPos.y()).arg(QApplication::desktop()->screenNumber(m_cursorPos));
+                    .arg(m_cursorPos.x()).arg(m_cursorPos.y()).arg(screenNum);
             if (QGuiApplication::mouseButtons() & Qt::LeftButton) {
                 QWindow *win = QGuiApplication::topLevelAt(m_cursorPos);
                 txt += QString(QLatin1String("Top-level window found? %1\n"))
@@ -234,6 +236,7 @@ void screenAdded(QScreen* screen)
     QList<QScreen *> screens = QGuiApplication::screens();
     int screenNumber = screens.indexOf(screen);
     Q_ASSERT(screenNumber >= 0);
+    // ### Qt 6: Find a replacement for QDesktopWidget::screen()
     w->setParent(qApp->desktop()->screen(screenNumber));
 
     w->show();