QScrollBar: Add createStandardContextMenu

Modeled after QLineEdit::createStandardContextMenu, allows customizing
the scroll bar context menu without re-implementing the entire menu.

[ChangeLog][QtWidgets][QScrollBar] Added createStandardContextMenu()
method to allow extending the built-in context menu.

Change-Id: I4f9feaba81a44a8c366b7341e0eb6934e9403a41
Reviewed-by: Axel Spoerl <axel.spoerl@qt.io>
Reviewed-by: Volker Hilsheimer <volker.hilsheimer@qt.io>

src/widgets/widgets/qscrollbar.cpp

@@ -9,17 +9,19 @@
 #include "qstyle.h"
 #include "qstyleoption.h"
 #include "qstylepainter.h"
-#if QT_CONFIG(menu)
-#include "qmenu.h"
-#endif
 
 #include <QtCore/qelapsedtimer.h>
 #include <QtCore/qpointer.h>
 
-
 #if QT_CONFIG(accessibility)
 #include "qaccessible.h"
 #endif
+
+#if QT_CONFIG(menu)
+#include "qmenu.h"
+#include "private/qmenu_p.h"
+#endif
+
 #include <limits.h>
 #include "qscrollbar_p.h"
 
@@ -27,6 +29,8 @@ using namespace std::chrono_literals;
 
 QT_BEGIN_NAMESPACE
 
+using namespace Qt::StringLiterals;
+
 /*!
     \class QScrollBar
     \brief The QScrollBar widget provides a vertical or horizontal scroll bar.
@@ -364,50 +368,96 @@ void QScrollBarPrivate::init()
 }
 
 #ifndef QT_NO_CONTEXTMENU
-/*! \reimp */
+/*!
+    \since 6.10
+
+    Creates the standard context menu, which is shown
+    when the user clicks on the scroll bar with the right mouse
+    button. It is called from the default contextMenuEvent() handler
+    and takes the \a position where the mouse click was in
+    this widget's local coordinates.
+    The popup menu's ownership is transferred to the caller.
+*/
+QMenu *QScrollBar::createStandardContextMenu(QPoint position)
+{
+#if QT_CONFIG(menu)
+    const bool horiz = HORIZONTAL;
+    QMenu *menu = new QMenu();
+    menu->setObjectName("qt_scrollbar_menu"_L1);
+
+    if (window() && window()->windowHandle()) {
+        if (auto *menuTopData = QMenuPrivate::get(menu)->topData())
+            menuTopData->initialScreen = window()->windowHandle()->screen();
+    }
+
+    menu->addAction(tr("Scroll here"), this, [this, horiz, position] {
+        setValue(d_func()->pixelPosToRangeValue(horiz ? position.x() : position.y()));
+    });
+    menu->addSeparator();
+    menu->addAction(horiz ? tr("Left edge") : tr("Top"), this, [this] {
+        triggerAction(QAbstractSlider::SliderToMinimum);
+    });
+    menu->addAction(horiz ? tr("Right edge") : tr("Bottom"), this, [this] {
+        triggerAction(QAbstractSlider::SliderToMaximum);
+    });
+    menu->addSeparator();
+    menu->addAction(horiz ? tr("Page left") : tr("Page up"), this, [this] {
+        triggerAction(QAbstractSlider::SliderPageStepSub);
+    });
+    menu->addAction(horiz ? tr("Page right") : tr("Page down"), this, [this] {
+        triggerAction(QAbstractSlider::SliderPageStepAdd);
+    });
+    menu->addSeparator();
+    menu->addAction(horiz ? tr("Scroll left") : tr("Scroll up"), this, [this] {
+        triggerAction(QAbstractSlider::SliderSingleStepSub);
+    });
+    menu->addAction(horiz ? tr("Scroll right") : tr("Scroll down"), this, [this] {
+        triggerAction(QAbstractSlider::SliderSingleStepAdd);
+    });
+    return menu;
+#else
+    Q_UNUSED(position);
+    return nullptr;
+#endif // QT_CONFIG(menu)
+}
+
+/*!
+    \reimp
+    \fn void QScrollBar::contextMenuEvent(QContextMenuEvent *event)
+
+    Shows the standard context menu created with createStandardContextMenu().
+
+    If you do not want the scroll bar to have a context menu, you can set
+    its \l contextMenuPolicy to Qt::NoContextMenu. A style can also control
+    this behavior using the SH_ScrollBar_ContextMenu hint.
+
+    If you want to customize the context menu, reimplement this function.
+    If you want to extend the standard context menu, reimplement this function,
+    call createStandardContextMenu() and extend the menu returned. Either store
+    the returned QMenu for later re-use or set the WA_DeleteOnClose attribute.
+
+    Information about the event is passed in the \a event object.
+*/
 void QScrollBar::contextMenuEvent(QContextMenuEvent *event)
 {
     if (!style()->styleHint(QStyle::SH_ScrollBar_ContextMenu, nullptr, this)) {
         QAbstractSlider::contextMenuEvent(event);
-        return ;
+        return;
     }
 
 #if QT_CONFIG(menu)
-    bool horiz = HORIZONTAL;
-    QPointer<QMenu> menu = new QMenu(this);
-    QAction *actScrollHere = menu->addAction(tr("Scroll here"));
-    menu->addSeparator();
-    QAction *actScrollTop =  menu->addAction(horiz ? tr("Left edge") : tr("Top"));
-    QAction *actScrollBottom = menu->addAction(horiz ? tr("Right edge") : tr("Bottom"));
-    menu->addSeparator();
-    QAction *actPageUp = menu->addAction(horiz ? tr("Page left") : tr("Page up"));
-    QAction *actPageDn = menu->addAction(horiz ? tr("Page right") : tr("Page down"));
-    menu->addSeparator();
-    QAction *actScrollUp = menu->addAction(horiz ? tr("Scroll left") : tr("Scroll up"));
-    QAction *actScrollDn = menu->addAction(horiz ? tr("Scroll right") : tr("Scroll down"));
-    QAction *actionSelected = menu->exec(event->globalPos());
-    delete menu;
-    if (actionSelected == nullptr)
-        /* do nothing */ ;
-    else if (actionSelected == actScrollHere)
-        setValue(d_func()->pixelPosToRangeValue(horiz ? event->pos().x() : event->pos().y()));
-    else if (actionSelected == actScrollTop)
-        triggerAction(QAbstractSlider::SliderToMinimum);
-    else if (actionSelected == actScrollBottom)
-        triggerAction(QAbstractSlider::SliderToMaximum);
-    else if (actionSelected == actPageUp)
-        triggerAction(QAbstractSlider::SliderPageStepSub);
-    else if (actionSelected == actPageDn)
-        triggerAction(QAbstractSlider::SliderPageStepAdd);
-    else if (actionSelected == actScrollUp)
-        triggerAction(QAbstractSlider::SliderSingleStepSub);
-    else if (actionSelected == actScrollDn)
-        triggerAction(QAbstractSlider::SliderSingleStepAdd);
-#endif // QT_CONFIG(menu)
+    QMenu *menu = createStandardContextMenu(event->pos());
+    if (!menu)
+        return;
+
+    menu->setAttribute(Qt::WA_DeleteOnClose);
+    menu->popup(event->globalPos());
+#else
+    Q_UNUSED(pos)
+#endif
 }
 #endif // QT_NO_CONTEXTMENU
 
-
 /*! \reimp */
 QSize QScrollBar::sizeHint() const
 {

src/widgets/widgets/qscrollbar.h

@@ -27,6 +27,10 @@ public:
     QSize sizeHint() const override;
     bool event(QEvent *event) override;
 
+#ifndef QT_NO_CONTEXTMENU
+    QMenu *createStandardContextMenu(QPoint position);
+#endif
+
 protected:
 #if QT_CONFIG(wheelevent)
     void wheelEvent(QWheelEvent *) override;