Add HasFrame feature to QStyleOptionTab

This makes it possible for styles like Fusion to draw tabbars different
when they have a frame.

Change-Id: I1bb21198c0c3caf44c757f6f39310bf2509054bf
Reviewed-by: J-P Nurmi <jpnurmi@digia.com>

src/widgets/styles/qstyleoption.cpp

@@ -1271,7 +1271,8 @@ QStyleOptionTab::QStyleOptionTab()
       row(0),
       position(Beginning),
       selectedPosition(NotAdjacent), cornerWidgets(QStyleOptionTab::NoCornerWidgets),
-      documentMode(false)
+      documentMode(false),
+      features(QStyleOptionTab::None)
 {
 }
 
@@ -1284,7 +1285,8 @@ QStyleOptionTab::QStyleOptionTab(int version)
       row(0),
       position(Beginning),
       selectedPosition(NotAdjacent), cornerWidgets(QStyleOptionTab::NoCornerWidgets),
-      documentMode(false)
+      documentMode(false),
+      features(QStyleOptionTab::None)
 {
 }
 
@@ -1437,6 +1439,17 @@ QStyleOptionTab::QStyleOptionTab(int version)
     The default value is false;
 */
 
+/*!
+    \enum QStyleOptionTab::TabFeature
+
+    Describes the various features that a tab button can have.
+
+    \value None A normal tab button.
+    \value HasFrame The tab button is positioned on a tab frame
+
+    \sa features
+*/
+
 /*!
     \variable QStyleOptionTab::leftButtonSize
     \brief the size for the left widget on the tab.

src/widgets/styles/qstyleoption.h

@@ -255,7 +255,9 @@ public:
     enum SelectedPosition { NotAdjacent, NextIsSelected, PreviousIsSelected };
     enum CornerWidget { NoCornerWidgets = 0x00, LeftCornerWidget = 0x01,
                         RightCornerWidget = 0x02 };
+    enum TabFeature { None = 0x00, HasFrame = 0x01 };
     Q_DECLARE_FLAGS(CornerWidgets, CornerWidget)
+    Q_DECLARE_FLAGS(TabFeatures, TabFeature)
 
     QTabBar::Shape shape;
     QString text;
@@ -268,6 +270,7 @@ public:
     bool documentMode;
     QSize leftButtonSize;
     QSize rightButtonSize;
+    TabFeatures features;
 
     QStyleOptionTab();
     QStyleOptionTab(const QStyleOptionTab &other) : QStyleOption(Version, Type) { *this = other; }

src/widgets/widgets/qtabbar.cpp

@@ -185,6 +185,7 @@ void QTabBar::initStyleOption(QStyleOptionTab *option, int tabIndex) const
 
 #ifndef QT_NO_TABWIDGET
     if (const QTabWidget *tw = qobject_cast<const QTabWidget *>(parentWidget())) {
+        option->features |= QStyleOptionTab::HasFrame;
         if (tw->cornerWidget(Qt::TopLeftCorner) || tw->cornerWidget(Qt::BottomLeftCorner))
             option->cornerWidgets |= QStyleOptionTab::LeftCornerWidget;
         if (tw->cornerWidget(Qt::TopRightCorner) || tw->cornerWidget(Qt::BottomRightCorner))