Unbreak binary compatibility in QStyleOptionHeader

4d94384612 introduced a new data member to
QStyleOptionHeader, and reduced the size of the orientation member.
This changed the binary layout of class instances, and breaks ABI.

180c662b07 added another member within
the new bitfield.

Introduce a new QStyleOptionHeaderV2 class instead with the new members,
and use that in QHeaderView, and the styles using the new members.

Fixes: QTBUG-91224
Pick-to: 6.1
Change-Id: I47e6841e6652e4b67f247b7b4514e90be5609156
Reviewed-by: David Faure <david.faure@kdab.com>

src/plugins/styles/mac/qmacstyle_mac.mm

@@ -3565,8 +3565,10 @@ void QMacStyle::drawControl(ControlElement ce, const QStyleOption *opt, QPainter
                 textr.translate(pixmap.width() / pixmap.devicePixelRatio() + 2, 0);
             }
             QString text = header->text;
-            if (header->textElideMode != Qt::ElideNone)
+            if (const QStyleOptionHeaderV2 *headerV2 = qstyleoption_cast<const QStyleOptionHeaderV2 *>(header)) {
-                text = header->fontMetrics.elidedText(text, header->textElideMode, textr.width());
+                if (headerV2->textElideMode != Qt::ElideNone)
+                    text = header->fontMetrics.elidedText(text, headerV2->textElideMode, textr.width());
+            }
 
             proxy()->drawItemText(p, textr, header->textAlignment | Qt::AlignVCenter, header->palette,
                                   header->state.testFlag(State_Enabled), text, QPalette::ButtonText);

src/widgets/itemviews/qheaderview.cpp

@@ -2910,6 +2910,7 @@ void QHeaderView::initStyleOptionForIndex(QStyleOptionHeader *option, int logica
     if (!option)
         return;
     QStyleOptionHeader &opt = *option;
+    QStyleOptionHeaderV2 *optV2 = qstyleoption_cast<QStyleOptionHeaderV2*>(option);
 
     QStyle::State state = QStyle::State_None;
     if (window()->isActiveWindow())
@@ -2953,7 +2954,8 @@ void QHeaderView::initStyleOptionForIndex(QStyleOptionHeader *option, int logica
                                         Qt::FontRole);
     if (var.isValid() && var.canConvert<QFont>())
         opt.fontMetrics = QFontMetrics(qvariant_cast<QFont>(var));
-    opt.textElideMode = d->textElideMode;
+    if (optV2)
+        optV2->textElideMode = d->textElideMode;
 
     QVariant foregroundBrush = d->model->headerData(logicalIndex, d->orientation,
                                                     Qt::ForegroundRole);
@@ -2992,7 +2994,8 @@ void QHeaderView::initStyleOptionForIndex(QStyleOptionHeader *option, int logica
         opt.selectedPosition = QStyleOptionHeader::NextIsSelected;
     else
         opt.selectedPosition = QStyleOptionHeader::NotAdjacent;
-    opt.isSectionDragTarget = d->target == logicalIndex;
+    if (optV2)
+        optV2->isSectionDragTarget = d->target == logicalIndex;
 }
 
 /*!
@@ -3007,7 +3010,7 @@ void QHeaderView::paintSection(QPainter *painter, const QRect &rect, int logical
     if (!rect.isValid())
         return;
 
-    QStyleOptionHeader opt;
+    QStyleOptionHeaderV2 opt;
     QPointF oldBO = painter->brushOrigin();
 
     initStyleOption(&opt);
@@ -3052,7 +3055,7 @@ QSize QHeaderView::sectionSizeFromContents(int logicalIndex) const
         return qvariant_cast<QSize>(variant);
 
     // otherwise use the contents
-    QStyleOptionHeader opt;
+    QStyleOptionHeaderV2 opt;
     initStyleOption(&opt);
     opt.section = logicalIndex;
     QVariant var = d->model->headerData(logicalIndex, d->orientation,

src/widgets/styles/qcommonstyle.cpp

@@ -1682,11 +1682,11 @@ void QCommonStyle::drawControl(ControlElement element, const QStyleOption *opt,
                 p->setFont(fnt);
                 fm = QFontMetrics((p->font()));
             }
-            QString text;
+            QString text = header->text;
-            if (header->textElideMode != Qt::ElideNone)
+            if (const QStyleOptionHeaderV2 *headerV2 = qstyleoption_cast<const QStyleOptionHeaderV2 *>(header)) {
-                text = fm.elidedText(header->text, header->textElideMode, rect.width());
+                if (headerV2->textElideMode != Qt::ElideNone)
-            else
+                    text = fm.elidedText(header->text, headerV2->textElideMode, rect.width());
-                text = header->text;
+            }
             proxy()->drawItemText(p, rect, header->textAlignment, header->palette,
                                   header->state.testFlag(State_Enabled), text, QPalette::ButtonText);
         }

src/widgets/styles/qfusionstyle.cpp

@@ -1280,10 +1280,12 @@ void QFusionStyle::drawControl(ControlElement element, const QStyleOption *optio
         painter->save();
         // Draws the header in tables.
         if (const QStyleOptionHeader *header = qstyleoption_cast<const QStyleOptionHeader *>(option)) {
+            const QStyleOptionHeaderV2 *headerV2 = qstyleoption_cast<const QStyleOptionHeaderV2 *>(option);
             QString pixmapName = QStyleHelper::uniqueName(QLatin1String("headersection"), option, option->rect.size());
             pixmapName += QString::number(- int(header->position));
             pixmapName += QString::number(- int(header->orientation));
-            pixmapName += QString::number(- int(header->isSectionDragTarget));
+            if (headerV2)
+                pixmapName += QString::number(- int(headerV2->isSectionDragTarget));
 
             QPixmap cache;
             if (!QPixmapCache::find(pixmapName, &cache)) {
@@ -1294,7 +1296,7 @@ void QFusionStyle::drawControl(ControlElement element, const QStyleOption *optio
                 QColor buttonColor = d->buttonColor(option->palette);
                 QColor gradientStartColor = buttonColor.lighter(104);
                 QColor gradientStopColor = buttonColor.darker(102);
-                if (header->isSectionDragTarget) {
+                if (headerV2 && headerV2->isSectionDragTarget) {
                     gradientStopColor = gradientStartColor.darker(130);
                     gradientStartColor = gradientStartColor.darker(130);
                 }

src/widgets/styles/qstyleoption.cpp

@@ -748,10 +748,32 @@ QStyleOptionHeader::QStyleOptionHeader(int version)
       section(0), textAlignment(Qt::AlignLeft), iconAlignment(Qt::AlignLeft),
       position(QStyleOptionHeader::Beginning),
       selectedPosition(QStyleOptionHeader::NotAdjacent), sortIndicator(None),
-      orientation(Qt::Horizontal), textElideMode(Qt::ElideNone), isSectionDragTarget(false), unused(0)
+      orientation(Qt::Horizontal)
 {
 }
 
+/*!
+    \class QStyleOptionHeaderV2
+    \brief The QStyleOptionHeaderV2 class is used to describe the
+    parameters for drawing a header.
+*/
+
+/*!
+    Constructs a QStyleOptionHeaderV2, initializing the members
+    variables to their default values.
+*/
+QStyleOptionHeaderV2::QStyleOptionHeaderV2()
+    : QStyleOptionHeaderV2(QStyleOptionHeader::Version)
+{
+}
+
+/*!
+    \internal
+*/
+QStyleOptionHeaderV2::QStyleOptionHeaderV2(int version)
+: QStyleOptionHeader(version), textElideMode(Qt::ElideNone), isSectionDragTarget(false), unused(0)
+{}
+
 /*!
     \variable QStyleOptionHeader::orientation
     \brief the header's orientation (horizontal or vertical)
@@ -892,7 +914,7 @@ QStyleOptionHeader::QStyleOptionHeader(int version)
 */
 
 /*!
-    \variable QStyleOptionHeader::textElideMode
+    \variable QStyleOptionHeaderV2::textElideMode
     \brief where ellipsis should be added for text that is too long to fit
     into an item
 

src/widgets/styles/qstyleoption.h

@@ -219,10 +219,7 @@ public:
     SectionPosition position;
     SelectedPosition selectedPosition;
     SortIndicator sortIndicator;
-    Qt::Orientation orientation:2;
+    Qt::Orientation orientation;
-    Qt::TextElideMode textElideMode:2;
-    bool isSectionDragTarget:1;
-    int unused:27;
 
     QStyleOptionHeader();
     QStyleOptionHeader(const QStyleOptionHeader &other) : QStyleOption(Version, Type) { *this = other; }
@@ -232,6 +229,24 @@ protected:
     QStyleOptionHeader(int version);
 };
 
+class Q_WIDGETS_EXPORT QStyleOptionHeaderV2 : public QStyleOptionHeader
+{
+public:
+    enum StyleOptionType { Type = SO_Header };
+    enum StyleOptionVersion { Version = 2 };
+
+    QStyleOptionHeaderV2();
+    QStyleOptionHeaderV2(const QStyleOptionHeaderV2 &other) : QStyleOptionHeader(Version) { *this = other; }
+    QStyleOptionHeaderV2 &operator=(const QStyleOptionHeaderV2 &) = default;
+
+    Qt::TextElideMode textElideMode:2;
+    bool isSectionDragTarget:1;
+    int unused:29;
+
+protected:
+    QStyleOptionHeaderV2(int version);
+};
+
 class Q_WIDGETS_EXPORT QStyleOptionButton : public QStyleOption
 {
 public: