Add a QSplashScreen constructor taking a QScreen

The constructor taking a QWidget is needed for specifying the screen
where the splash screen should be displayed.

Add a new constructor for specifying the target screen for the splash screen
directly, instead of "extracting" the screen information from a widget.
This removes the need for using the deprecated QDesktopWidget.

Deprecate the constructor taking a QWidget.

Task-number: QTBUG-76491
Change-Id: I1dde242ff5f7b53e52af308bb685f492d6266d33
Reviewed-by: Tor Arne Vestbø <tor.arne.vestbo@qt.io>

src/widgets/doc/snippets/qsplashscreen/main.cpp

@@ -71,3 +71,10 @@ int main(int argc, char *argv[])
     return app.exec();
 }
 //! [1]
+
+//! [2]
+QScreen *screen = QGuiApplication::screens().at(1);
+QPixmap pixmap(":/splash.png");
+QSplashScreen splash(screen, pixmap);
+splash.show();
+//! [2]

src/widgets/widgets/qsplashscreen.cpp

@@ -123,6 +123,11 @@ public:
    wish to do your own drawing you can get a pointer to the pixmap
    used in the splash screen with pixmap().  Alternatively, you can
    subclass QSplashScreen and reimplement drawContents().
+
+   In case of having multiple screens, it is also possible to show the
+   splash screen on a different screen than the primary one. For example:
+
+   \snippet qsplashscreen/main.cpp 2
 */
 
 /*!
@@ -139,6 +144,23 @@ QSplashScreen::QSplashScreen(const QPixmap &pixmap, Qt::WindowFlags f)
 
 /*!
     \overload
+    \since 5.15
+
+    This function allows you to specify the screen for your splashscreen. The
+    typical use for this constructor is if you have multiple screens and
+    prefer to have the splash screen on a different screen than your primary
+    one. In that case pass the proper \a screen.
+*/
+QSplashScreen::QSplashScreen(QScreen *screen, const QPixmap &pixmap, Qt::WindowFlags f)
+    : QWidget(*(new QSplashScreenPrivate()), nullptr, Qt::SplashScreen | Qt::FramelessWindowHint | f)
+{
+    d_func()->setPixmap(pixmap, screen);
+}
+
+#if QT_DEPRECATED_SINCE(5, 15)
+/*!
+    \overload
+    \obsolete
 
     This function allows you to specify a parent for your splashscreen. The
     typical use for this constructor is if you have a multiple screens and
@@ -152,6 +174,7 @@ QSplashScreen::QSplashScreen(QWidget *parent, const QPixmap &pixmap, Qt::WindowF
     // is still 0 here due to QWidget's special handling.
     d_func()->setPixmap(pixmap, QSplashScreenPrivate::screenFor(parent));
 }
+#endif
 
 /*!
   Destructor.
@@ -286,26 +309,35 @@ void QSplashScreen::setPixmap(const QPixmap &pixmap)
 }
 
 // In setPixmap(), resize and try to position on a screen according to:
-// 1) If a QDesktopScreenWidget is found in the parent hierarchy, use that (see docs on
+// 1) If the screen for the given widget is available, use that
+// 2) If a QDesktopScreenWidget is found in the parent hierarchy, use that (see docs on
 //    QSplashScreen(QWidget *, QPixmap).
-// 2) If a widget with associated QWindow is found, use that
-// 3) When nothing can be found, try to center it over the cursor
+// 3) If a widget with associated QWindow is found, use that
+// 4) When nothing can be found, try to center it over the cursor
 
+#if QT_DEPRECATED_SINCE(5, 15)
 static inline int screenNumberOf(const QDesktopScreenWidget *dsw)
 {
     auto desktopWidgetPrivate =
         static_cast<QDesktopWidgetPrivate *>(qt_widget_private(QApplication::desktop()));
     return desktopWidgetPrivate->screens.indexOf(const_cast<QDesktopScreenWidget *>(dsw));
 }
+#endif
 
 const QScreen *QSplashScreenPrivate::screenFor(const QWidget *w)
 {
+    if (w && w->screen())
+        return w->screen();
+
     for (const QWidget *p = w; p !=nullptr ; p = p->parentWidget()) {
+#if QT_DEPRECATED_SINCE(5, 15)
         if (auto dsw = qobject_cast<const QDesktopScreenWidget *>(p))
             return QGuiApplication::screens().value(screenNumberOf(dsw));
+#endif
         if (QWindow *window = p->windowHandle())
             return window->screen();
     }
+
 #if QT_CONFIG(cursor)
     // Note: We could rely on QPlatformWindow::initialGeometry() to center it
     // over the cursor, but not all platforms (namely Android) use that.

src/widgets/widgets/qsplashscreen.h

@@ -55,7 +55,11 @@ class Q_WIDGETS_EXPORT QSplashScreen : public QWidget
     Q_OBJECT
 public:
     explicit QSplashScreen(const QPixmap &pixmap = QPixmap(), Qt::WindowFlags f = Qt::WindowFlags());
+    QSplashScreen(QScreen *screen, const QPixmap &pixmap = QPixmap(), Qt::WindowFlags f = Qt::WindowFlags());
+#if QT_DEPRECATED_SINCE(5, 15)
+    QT_DEPRECATED_VERSION_X_5_15("Use the constructor taking a QScreen *")
     QSplashScreen(QWidget *parent, const QPixmap &pixmap = QPixmap(), Qt::WindowFlags f = Qt::WindowFlags());
+#endif
     virtual ~QSplashScreen();
 
     void setPixmap(const QPixmap &pixmap);

tests/auto/widgets/widgets/qsplashscreen/tst_qsplashscreen.cpp

@@ -36,6 +36,7 @@ class tst_QSplashScreen : public QObject
 
 private slots:
     void checkCloseTime();
+    void checkScreenConstructor();
 };
 
 class CloseEventSplash : public QSplashScreen
@@ -69,5 +70,16 @@ void tst_QSplashScreen::checkCloseTime()
     QVERIFY(w.windowHandle()->isExposed());
 }
 
+void tst_QSplashScreen::checkScreenConstructor()
+{
+    for (const auto screen : QGuiApplication::screens()) {
+        QSplashScreen splash(screen);
+        splash.show();
+        QCOMPARE(splash.screen(), screen);
+        QVERIFY(splash.windowHandle());
+        QCOMPARE(splash.windowHandle()->screen(), screen);
+    }
+}
+
 QTEST_MAIN(tst_QSplashScreen)
 #include "tst_qsplashscreen.moc"