Fix hover handling in QTreeView

Cached hoverBranch could get invalid if branches were collapsed or
expanded programmatically, leading to a crash in some situations.

Fixed the logic for updating hovered over branch indicators and
also now update hoverBranch when drawing so that it is guaranteed to be
up to date there - this fixes issues like hover indicator not updating
when the view is programmatically scrolled.

Task-number: QTBUG-27158
Change-Id: I5bd1ad76aee512ad78df33959a84ead16886a47c
Reviewed-by: Stephen Kelly <stephen.kelly@kdab.com>
(cherry picked from qt5/qtbase commit fd6a870136ab2fdb3ce8b516abcf8c05d45caba7))

2 files changed, 12 insertions, 14 deletions

diff --git a/src/gui/itemviews/qtreeview.cpp b/src/gui/itemviews/qtreeview.cpp
index 15ec9a4..97d23a5 100644
--- a/src/gui/itemviews/qtreeview.cpp
+++ b/src/gui/itemviews/qtreeview.cpp
@@ -1236,19 +1236,14 @@ bool QTreeView::viewportEvent(QEvent *event)
         QHoverEvent *he = static_cast<QHoverEvent*>(event);
         int oldBranch = d->hoverBranch;
         d->hoverBranch = d->itemDecorationAt(he->pos());
-        if (oldBranch != d->hoverBranch) {
-            //we need to paint the whole items (including the decoration) so that when the user
-            //moves the mouse over those elements they are updated
-            if (oldBranch >= 0) {
-                int y = d->coordinateForItem(oldBranch);
-                int h = d->itemHeight(oldBranch);
-                viewport()->update(QRect(0, y, viewport()->width(), h));
-            }
-            if (d->hoverBranch >= 0) {
-                int y = d->coordinateForItem(d->hoverBranch);
-                int h = d->itemHeight(d->hoverBranch);
-                viewport()->update(QRect(0, y, viewport()->width(), h));
-            }
+        QModelIndex newIndex = indexAt(he->pos());
+        if (d->hover != newIndex || d->hoverBranch != oldBranch) {
+            // Update the whole hovered over row. No need to update the old hovered
+            // row, that is taken care in superclass hover handling.
+            QRect rect = visualRect(newIndex);
+            rect.setX(0);
+            rect.setWidth(viewport()->width());
+            viewport()->update(rect);
         }
         break; }
     default:
@@ -1414,6 +1409,9 @@ void QTreeView::drawTree(QPainter *painter, const QRegion &region) const
 
     const int viewportWidth = d->viewport->width();
 
+    QPoint hoverPos = d->viewport->mapFromGlobal(QCursor::pos());
+    d->hoverBranch = d->itemDecorationAt(hoverPos);
+
     QVector<QRect> rects = region.rects();
     QVector<int> drawn;
     bool multipleRects = (rects.size() > 1);
diff --git a/src/gui/itemviews/qtreeview_p.h b/src/gui/itemviews/qtreeview_p.h
index 250bdab..b52ccae 100644
--- a/src/gui/itemviews/qtreeview_p.h
+++ b/src/gui/itemviews/qtreeview_p.h
@@ -244,7 +244,7 @@ public:
     QBasicTimer openTimer;
 
     // used for drawing hilighted expand/collapse indicators
-    int hoverBranch;
+    mutable int hoverBranch;
 
     // used for blocking recursion when calling setViewportMargins from updateGeometries
     bool geometryRecursionBlock;