QtWidgets: replace uses of inefficient QList<QPair>s with QVectors

These QPairs are larger than a void*, so holding them in QLists
is needlessly inefficient. Worse, the code could come to depend
on the fragile property of (inefficient) QLists that references
to elements therein never are invalidated.

Fix by holding them in QVector instead.

Change-Id: I3c205f5326cfd96482563078bdca1747d718457f
Reviewed-by: Olivier Goffart (Woboq GmbH) <ogoffart@woboq.com>

2 files changed, 7 insertions, 6 deletions

diff --git a/src/widgets/itemviews/qtreeview.cpp b/src/widgets/itemviews/qtreeview.cpp
index e7d8fc9783..fdd2be69eb 100644
--- a/src/widgets/itemviews/qtreeview.cpp
+++ b/src/widgets/itemviews/qtreeview.cpp
@@ -3777,8 +3777,8 @@ QRect QTreeViewPrivate::itemDecorationRect(const QModelIndex &index) const
     return q->style()->subElementRect(QStyle::SE_TreeViewDisclosureItem, &opt, q);
 }
 
-QList<QPair<int, int> > QTreeViewPrivate::columnRanges(const QModelIndex &topIndex,
-                                                          const QModelIndex &bottomIndex) const
+QVector<QPair<int, int> > QTreeViewPrivate::columnRanges(const QModelIndex &topIndex,
+                                                         const QModelIndex &bottomIndex) const
 {
     const int topVisual = header->visualIndex(topIndex.column()),
         bottomVisual = header->visualIndex(bottomIndex.column());
@@ -3798,7 +3798,7 @@ QList<QPair<int, int> > QTreeViewPrivate::columnRanges(const QModelIndex &topInd
     //let's sort the list
     std::sort(logicalIndexes.begin(), logicalIndexes.end());
 
-    QList<QPair<int, int> > ret;
+    QVector<QPair<int, int> > ret;
     QPair<int, int> current;
     current.first = -2; // -1 is not enough because -1+1 = 0
     current.second = -2;
@@ -3832,8 +3832,8 @@ void QTreeViewPrivate::select(const QModelIndex &topIndex, const QModelIndex &bo
     const int top = viewIndex(topIndex),
         bottom = viewIndex(bottomIndex);
 
-    const QList< QPair<int, int> > colRanges = columnRanges(topIndex, bottomIndex);
-    QList< QPair<int, int> >::const_iterator it;
+    const QVector<QPair<int, int> > colRanges = columnRanges(topIndex, bottomIndex);
+    QVector<QPair<int, int> >::const_iterator it;
     for (it = colRanges.begin(); it != colRanges.end(); ++it) {
         const int left = (*it).first,
             right = (*it).second;
diff --git a/src/widgets/itemviews/qtreeview_p.h b/src/widgets/itemviews/qtreeview_p.h
index 9d2f496c5d..a3619ce13b 100644
--- a/src/widgets/itemviews/qtreeview_p.h
+++ b/src/widgets/itemviews/qtreeview_p.h
@@ -54,6 +54,7 @@
 #include "private/qabstractitemview_p.h"
 #include <QtCore/qvariantanimation.h>
 #include <QtCore/qabstractitemmodel.h>
+#include <QtCore/qvector.h>
 
 #ifndef QT_NO_TREEVIEW
 
@@ -164,7 +165,7 @@ public:
     QRect itemDecorationRect(const QModelIndex &index) const;
 
 
-    QList<QPair<int, int> > columnRanges(const QModelIndex &topIndex, const QModelIndex &bottomIndex) const;
+    QVector<QPair<int, int> > columnRanges(const QModelIndex &topIndex, const QModelIndex &bottomIndex) const;
     void select(const QModelIndex &start, const QModelIndex &stop, QItemSelectionModel::SelectionFlags command);
 
     QPair<int,int> startAndEndColumns(const QRect &rect) const;