Expose ItemViewActivateItemOnSingleClick in QStyleHints

This completes support for ItemViewActivateItemOnSingleClick in
QPlatformIntegration and exposes the setting in QStyleHints.

Based on the review process, the public name used is
'singleClickActivation' for brevity, as well as to avoid con-
fusion over alluding to "item views" in the Qt Quick context.

KDE Plasma intends to use this via Qt.styleHints to have
Qt Quick-based UI correctly implement the global single vs.
double click user preference for item activation.

[ChangeLog][QtGui] Added QStyleHints::singleClickActivation
to access whether the platform expects item activation to
occur on single clicks rather than double clicks.

Change-Id: I0916e9e68c3a157f95053da8227b2612803653f7
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@theqtcompany.com>

src/gui/kernel/qplatformintegration.cpp

@@ -396,6 +396,8 @@ QVariant QPlatformIntegration::styleHint(StyleHint hint) const
         return QPlatformTheme::defaultThemeHint(QPlatformTheme::TabFocusBehavior);
     case ReplayMousePressOutsidePopup:
         return true;
+    case ItemViewActivateItemOnSingleClick:
+        return QPlatformTheme::defaultThemeHint(QPlatformTheme::ItemViewActivateItemOnSingleClick);
     }
 
     return 0;

src/gui/kernel/qplatformintegration.h

@@ -147,7 +147,8 @@ public:
         ShowIsMaximized,
         MousePressAndHoldInterval,
         TabFocusBehavior,
-        ReplayMousePressOutsidePopup
+        ReplayMousePressOutsidePopup,
+        ItemViewActivateItemOnSingleClick
     };
 
     virtual QVariant styleHint(StyleHint hint) const;

src/gui/kernel/qplatformtheme.cpp

@@ -434,6 +434,8 @@ QVariant QPlatformTheme::themeHint(ThemeHint hint) const
         return QGuiApplicationPrivate::platformIntegration()->styleHint(QPlatformIntegration::PasswordMaskCharacter);
     case QPlatformTheme::MousePressAndHoldInterval:
         return QGuiApplicationPrivate::platformIntegration()->styleHint(QPlatformIntegration::MousePressAndHoldInterval);
+    case QPlatformTheme::ItemViewActivateItemOnSingleClick:
+        return QGuiApplicationPrivate::platformIntegration()->styleHint(QPlatformIntegration::ItemViewActivateItemOnSingleClick);
     default:
         return QPlatformTheme::defaultThemeHint(hint);
     }

src/gui/kernel/qstylehints.cpp

@@ -377,4 +377,16 @@ Qt::TabFocusBehavior QStyleHints::tabFocusBehavior() const
     return Qt::TabFocusBehavior(themeableHint(QPlatformTheme::TabFocusBehavior, QPlatformIntegration::TabFocusBehavior).toInt());
 }
 
+/*!
+    \property QStyleHints::singleClickActivation
+    \brief \c true if items should be activated by single click, \b false
+    if they should be activated by double click instead.
+
+    \since 5.5
+*/
+bool QStyleHints::singleClickActivation() const
+{
+    return themeableHint(QPlatformTheme::ItemViewActivateItemOnSingleClick, QPlatformIntegration::ItemViewActivateItemOnSingleClick).toBool();
+}
+
 QT_END_NAMESPACE

src/gui/kernel/qstylehints.h

@@ -61,6 +61,7 @@ class Q_GUI_EXPORT QStyleHints : public QObject
     Q_PROPERTY(int startDragVelocity READ startDragVelocity STORED false CONSTANT FINAL)
     Q_PROPERTY(bool useRtlExtensions READ useRtlExtensions STORED false CONSTANT FINAL)
     Q_PROPERTY(Qt::TabFocusBehavior tabFocusBehavior READ tabFocusBehavior STORED false CONSTANT FINAL)
+    Q_PROPERTY(bool singleClickActivation READ singleClickActivation STORED false CONSTANT FINAL)
 
 public:
     void setMouseDoubleClickInterval(int mouseDoubleClickInterval);
@@ -83,6 +84,7 @@ public:
     bool useRtlExtensions() const;
     bool setFocusOnTouchRelease() const;
     Qt::TabFocusBehavior tabFocusBehavior() const;
+    bool singleClickActivation() const;
 
 Q_SIGNALS:
     void cursorFlashTimeChanged(int cursorFlashTime);