Port away from QDesktopWidget

This ports Shell from QDesktopWidget to QScreen (trivial),
and removes unused QDesktopWidget includes (super-trivial).

core/utils.cpp

@@ -15,11 +15,11 @@
 #include "settings_core.h"
 
 #include <QApplication>
-#include <QDesktopWidget>
 #include <QIODevice>
 #include <QImage>
 #include <QRect>
 #include <QScreen>
+#include <QWidget>
 #include <QWindow>
 
 using namespace Okular;

shell/shell.cpp

@@ -40,12 +40,12 @@
 #include <KXMLGUIFactory>
 #include <QApplication>
 #include <QDBusConnection>
-#include <QDesktopWidget>
 #include <QDragMoveEvent>
 #include <QFileDialog>
 #include <QMenuBar>
 #include <QMimeDatabase>
 #include <QMimeType>
+#include <QScreen>
 #include <QTabBar>
 #include <QTabWidget>
 #include <QTimer>
@@ -545,7 +545,7 @@ void Shell::slotShowMenubar()
 
 QSize Shell::sizeHint() const
 {
-    return QApplication::desktop()->availableGeometry(this).size() * 0.75;
+    return QApplication::primaryScreen()->availableSize() * 0.75;
 }
 
 bool Shell::queryClose()

ui/propertiesdialog.cpp

@@ -11,7 +11,6 @@
 
 // qt/kde includes
 #include <QApplication>
-#include <QDesktopWidget>
 #include <QFile>
 #include <QFileDialog>
 #include <QFormLayout>