Introduce QWidget::setScreen

Follows the QWindow semantics, and is a replacement for creating
a QWidget with a QDesktopScreenWidget as the parent.

We can now remove much of the special handling of QDesktopWidget and
the Qt::Desktop window type, and get rid of QDesktopScreenWidget.

Add a manual test that allows local testing. Our CI environments
only have a single screen, and no multi-head display server setup
which is the primary case where QWidget::setScreen is interesting.
For the more common case of a virtual desktop, QWidget::setScreen
has no real impact (just as QWindow::setScreen doesn't).

Change-Id: Id0099e069d316741bacd8c795c396ccad37be297
Fixes: QTBUG-85483
Reviewed-by: Tor Arne Vestbø <tor.arne.vestbo@qt.io>

1 files changed, 1 insertions, 2 deletions

diff --git a/src/widgets/kernel/qwidget.h b/src/widgets/kernel/qwidget.h
index 2bfff96252..6f4c709c10 100644
--- a/src/widgets/kernel/qwidget.h
+++ b/src/widgets/kernel/qwidget.h
@@ -598,11 +598,10 @@ public:
 
     QWindow *windowHandle() const;
     QScreen *screen() const;
+    void setScreen(QScreen *);
 
     static QWidget *createWindowContainer(QWindow *window, QWidget *parent=nullptr, Qt::WindowFlags flags=Qt::WindowFlags());
 
-    friend class QDesktopScreenWidget;
-
 Q_SIGNALS:
     void windowTitleChanged(const QString &title);
     void windowIconChanged(const QIcon &icon);