Phase 2 of removing QDesktopWidget

Remove QDestopWidget public header, simplify the implementation that
maintains a Qt::Desktop type QWidget for each QScreen, and turn
QWidget's initial target screen into a QScreen pointer.

QApplication::desktop() now takes an optional QScreen pointer, and
returns a QWidget pointer, so that applications and widgets can get
access to the root widget for a specific screen without having to
resort to private APIs.

QDesktopWidgetPrivate implementations to look up a screen for an index,
widget, or point are now all inline functions that thinly wrap
QGuiApplication::screens/screenAt calls. We should consider adding those
as convenience APIs to QScreen instead.

Note that QWidget::screen is assumed to return a valid pointer; there is
code that handles the case that it returns nullptr (but also code that
trusts that it never is nullptr), so this needs to be defined, verified
with tests, and asserted. We can then simplify the code further.

Change-Id: Ifc89be65a0dce265b6729feaf54121c35137cb94
Reviewed-by: Shawn Rutledge <shawn.rutledge@qt.io>
Reviewed-by: Tor Arne Vestbø <tor.arne.vestbo@qt.io>
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>

3 files changed, 3 insertions, 6 deletions

diff --git a/src/widgets/util/qcompleter.cpp b/src/widgets/util/qcompleter.cpp
index 926eee26f3..72084ebd8f 100644
--- a/src/widgets/util/qcompleter.cpp
+++ b/src/widgets/util/qcompleter.cpp
@@ -157,7 +157,6 @@
 #endif
 #include "QtWidgets/qapplication.h"
 #include "QtGui/qevent.h"
-#include "QtWidgets/qdesktopwidget.h"
 #include <private/qapplication_p.h>
 #include <private/qdesktopwidget_p.h>
 #if QT_CONFIG(lineedit)
@@ -921,7 +920,7 @@ void QCompleterPrivate::_q_autoResizePopup()
 
 void QCompleterPrivate::showPopup(const QRect& rect)
 {
-    const QRect screen = QDesktopWidgetPrivate::availableGeometry(widget);
+    const QRect screen = QWidgetPrivate::availableScreenGeometry(widget);
     Qt::LayoutDirection dir = widget->layoutDirection();
     QPoint pos;
     int rh, w;
diff --git a/src/widgets/util/qscroller.cpp b/src/widgets/util/qscroller.cpp
index fec373d45c..003f27de56 100644
--- a/src/widgets/util/qscroller.cpp
+++ b/src/widgets/util/qscroller.cpp
@@ -57,7 +57,6 @@
 #include <QGraphicsScene>
 #include <QGraphicsView>
 #endif
-#include <QDesktopWidget>
 #include <private/qdesktopwidget_p.h>
 #include <QVector2D>
 #include <QtCore/qmath.h>
diff --git a/src/widgets/util/qsystemtrayicon.cpp b/src/widgets/util/qsystemtrayicon.cpp
index e4ee5770f1..170eba7514 100644
--- a/src/widgets/util/qsystemtrayicon.cpp
+++ b/src/widgets/util/qsystemtrayicon.cpp
@@ -60,7 +60,6 @@
 #include "qstyle.h"
 #include "qgridlayout.h"
 #include "qapplication.h"
-#include "qdesktopwidget.h"
 #include <private/qdesktopwidget_p.h>
 #include "qbitmap.h"
 
@@ -132,7 +131,7 @@ static QIcon messageIcon2qIcon(QSystemTrayIcon::MessageIcon icon)
     of type QEvent::ToolTip. Additionally, the QSystemTrayIcon receives wheel events of
     type QEvent::Wheel. These are not supported on any other platform.
 
-    \sa QDesktopServices, QDesktopWidget, {Desktop Integration}, {System Tray Icon Example}
+    \sa QDesktopServices, {Desktop Integration}, {System Tray Icon Example}
 */
 
 /*!
@@ -533,7 +532,7 @@ QBalloonTip::QBalloonTip(const QIcon &icon, const QString &title,
     msgLabel->setAlignment(Qt::AlignTop | Qt::AlignLeft);
 
     // smart size for the message label
-    int limit = QDesktopWidgetPrivate::availableGeometry(msgLabel).size().width() / 3;
+    int limit = QWidgetPrivate::availableScreenGeometry(msgLabel).width() / 3;
     if (msgLabel->sizeHint().width() > limit) {
         msgLabel->setWordWrap(true);
         if (msgLabel->sizeHint().width() > limit) {