Implement private visualRect() in QTreeView and QAbstractItemView

QTreeView::visualRect() returns a given model index's visual rectangle.
The method is used to toggle the background during hovering.
The previous implementation included the row indicator, when the first
row section was hovered. When it was unhovered, the row indicator
remained highlighted, until the mouse had left the view port.

The reason is, that the highlighting implementation changed the
rectangle returned for the first section, to include the row indicator.
The implementation for neutralising a highlighted section relies on
QAbstractItemViewPrivate::setHoverIndex() and
QAbstractItemView::update(). These methods don't know about the row
indicator to be included, and therefore do not update() its rectangle.
As a consequence, the correct background gets painted but not updated
on the screen.

This patch moves the calculation of the visual rectangle to a new
QTreeViewPrivate::visualRect_impl(). In addition to the model index,
the new method expects an enum argument, representing the calculation
rule:
- SingleSection: Calculate the rectangle of the given section.
- FullRow: Returns the rectangle of the entire row, regardless of the
index's column.
- AddRowIndiCatorToFirstCulumn: Adds the row indicator to the rect,
if the model index points to the first column.

The patch updates all calls within QTreeView, to use the private method
with the right calculation rule for the use case at hand. It elminates
manual (and repeated) modifications of the return value.

The patch implements QAbstractItemViewPrivate::visualRect(), which
returns QAbstractItemView::visualRect(). It is overridden in
QTreeViewPrivate, so that QAbstractItemViewPrivate::setHoverIndex()
and QAbstractItemView receive the rectangle including row indicator.

As a drive-by, several local variables have been constified and/or
renamed to indicative variable names.

Fixes: QTBUG-115149
Pick-to: 6.6 6.5
Change-Id: I4838bcf744f87d8cfb259c5d8758fb65e091e9fe
Reviewed-by: Tor Arne Vestbø <tor.arne.vestbo@qt.io>

1 files changed, 2 insertions, 0 deletions

diff --git a/src/widgets/itemviews/qabstractitemview_p.h b/src/widgets/itemviews/qabstractitemview_p.h
index bd859e1332..f016f085d8 100644
--- a/src/widgets/itemviews/qabstractitemview_p.h
+++ b/src/widgets/itemviews/qabstractitemview_p.h
@@ -417,6 +417,8 @@ public:
     bool verticalScrollModeSet;
     bool horizontalScrollModeSet;
 
+    virtual QRect visualRect(const QModelIndex &index) const { return q_func()->visualRect(index); }
+
 private:
     inline QAbstractItemDelegate *delegateForIndex(const QModelIndex &index) const {
         QMap<int, QPointer<QAbstractItemDelegate> >::ConstIterator it;