QHeaderView: Mark the drop section during section move

Currently there is no visual feedback where the section move will end
up. Therefore mark the drop section to show where the dragged section
will be inserted.

Fixes: QTBUG-673
Fixes: QTBUG-1114
Change-Id: I3e45a9a9c0604342bb0286fc7cd4c89c757c28cd
Reviewed-by: Richard Moe Gustavsen <richard.gustavsen@qt.io>

5 files changed, 37 insertions, 5 deletions

diff --git a/src/widgets/itemviews/qheaderview.cpp b/src/widgets/itemviews/qheaderview.cpp
index 8ddbbd903a..e815ff53fa 100644
--- a/src/widgets/itemviews/qheaderview.cpp
+++ b/src/widgets/itemviews/qheaderview.cpp
@@ -2572,7 +2572,8 @@ void QHeaderView::mousePressEvent(QMouseEvent *e)
             acceptMoveSection = false; // Do not allow moving the tree nod
 
         if (acceptMoveSection) {
-            d->section = d->target = d->pressed;
+            d->target = -1;
+            d->section = d->pressed;
             if (d->section == -1)
                 return;
             d->state = QHeaderViewPrivate::MoveSection;
@@ -2645,6 +2646,7 @@ void QHeaderView::mouseMoveEvent(QMouseEvent *e)
                 const int posThreshold = d->headerSectionPosition(visual) - d->offset + d->headerSectionSize(visual) / 2;
                 const int checkPos = d->reverse() ? d->viewport->width() - pos : pos;
                 int moving = visualIndex(d->section);
+                int oldTarget = d->target;
                 if (visual < moving) {
                     if (checkPos < posThreshold)
                         d->target = d->logicalIndex(visual);
@@ -2658,6 +2660,8 @@ void QHeaderView::mouseMoveEvent(QMouseEvent *e)
                 } else {
                     d->target = d->section;
                 }
+                if (oldTarget != d->target || oldTarget == -1)
+                    d->updateSectionsBeforeAfter(d->target);
                 d->updateSectionIndicator(d->section, pos);
             }
             return;
@@ -2729,6 +2733,8 @@ void QHeaderView::mouseReleaseEvent(QMouseEvent *e)
             moveSection(from, to);
             d->section = d->target = -1;
             d->updateSectionIndicator(d->section, pos);
+            if (from == to)
+                d->updateSectionsBeforeAfter(from);
             break;
         } // not moving
         Q_FALLTHROUGH();
@@ -2986,6 +2992,7 @@ void QHeaderView::initStyleOptionForIndex(QStyleOptionHeader *option, int logica
         opt.selectedPosition = QStyleOptionHeader::NextIsSelected;
     else
         opt.selectedPosition = QStyleOptionHeader::NotAdjacent;
+    opt.isSectionDragTarget = d->target == logicalIndex;
 }
 
 /*!
@@ -4047,6 +4054,25 @@ void QHeaderViewPrivate::setScrollOffset(const QScrollBar *scrollBar, QAbstractI
     }
 }
 
+void QHeaderViewPrivate::updateSectionsBeforeAfter(int logical)
+{
+    Q_Q(QHeaderView);
+    const int visual = visualIndex(logical);
+    int from = logicalIndex(visual > 1 ? visual - 1 : 0);
+    int to = logicalIndex(visual + 1 >= sectionCount() ? visual : visual + 1);
+    QRect updateRect;
+    if (orientation == Qt::Horizontal) {
+        if (reverse())
+            std::swap(from, to);
+        updateRect = QRect(QPoint(q->sectionViewportPosition(from), 0),
+                           QPoint(q->sectionViewportPosition(to) + headerSectionSize(to), viewport->height()));
+    } else {
+        updateRect = QRect(QPoint(0, q->sectionViewportPosition(from)),
+                           QPoint(viewport->width(), q->sectionViewportPosition(to) + headerSectionSize(to)));
+    }
+    viewport->update(updateRect);
+}
+
 #ifndef QT_NO_DATASTREAM
 void QHeaderViewPrivate::write(QDataStream &out) const
 {
diff --git a/src/widgets/itemviews/qheaderview_p.h b/src/widgets/itemviews/qheaderview_p.h
index 7c1ff94646..e8a096bf98 100644
--- a/src/widgets/itemviews/qheaderview_p.h
+++ b/src/widgets/itemviews/qheaderview_p.h
@@ -385,6 +385,7 @@ public:
     int viewSectionSizeHint(int logical) const;
     int adjustedVisualIndex(int visualIndex) const;
     void setScrollOffset(const QScrollBar *scrollBar, QAbstractItemView::ScrollMode scrollMode);
+    void updateSectionsBeforeAfter(int logical);
 
 #ifndef QT_NO_DATASTREAM
     void write(QDataStream &out) const;
diff --git a/src/widgets/styles/qfusionstyle.cpp b/src/widgets/styles/qfusionstyle.cpp
index b8044dbc09..d2eb5e25cc 100644
--- a/src/widgets/styles/qfusionstyle.cpp
+++ b/src/widgets/styles/qfusionstyle.cpp
@@ -1283,6 +1283,7 @@ void QFusionStyle::drawControl(ControlElement element, const QStyleOption *optio
             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));
 
             QPixmap cache;
             if (!QPixmapCache::find(pixmapName, &cache)) {
@@ -1291,9 +1292,12 @@ void QFusionStyle::drawControl(ControlElement element, const QStyleOption *optio
                 QRect pixmapRect(0, 0, rect.width(), rect.height());
                 QPainter cachePainter(&cache);
                 QColor buttonColor = d->buttonColor(option->palette);
-                QColor gradientStopColor;
                 QColor gradientStartColor = buttonColor.lighter(104);
-                gradientStopColor = buttonColor.darker(102);
+                QColor gradientStopColor = buttonColor.darker(102);
+                if (header->isSectionDragTarget) {
+                    gradientStopColor = gradientStartColor.darker(130);
+                    gradientStartColor = gradientStartColor.darker(130);
+                }
                 QLinearGradient gradient(pixmapRect.topLeft(), pixmapRect.bottomLeft());
 
                 if (option->palette.window().gradient()) {
diff --git a/src/widgets/styles/qstyleoption.cpp b/src/widgets/styles/qstyleoption.cpp
index 6e994dc8dc..933603dd7e 100644
--- a/src/widgets/styles/qstyleoption.cpp
+++ b/src/widgets/styles/qstyleoption.cpp
@@ -748,7 +748,7 @@ 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), unused(0)
+      orientation(Qt::Horizontal), textElideMode(Qt::ElideNone), isSectionDragTarget(false), unused(0)
 {
 }
 
diff --git a/src/widgets/styles/qstyleoption.h b/src/widgets/styles/qstyleoption.h
index 4998d8cf14..677a04c04b 100644
--- a/src/widgets/styles/qstyleoption.h
+++ b/src/widgets/styles/qstyleoption.h
@@ -221,7 +221,8 @@ public:
     SortIndicator sortIndicator;
     Qt::Orientation orientation:2;
     Qt::TextElideMode textElideMode:2;
-    int unused:28;
+    bool isSectionDragTarget:1;
+    int unused:27;
 
     QStyleOptionHeader();
     QStyleOptionHeader(const QStyleOptionHeader &other) : QStyleOption(Version, Type) { *this = other; }