designer: Fix MSVC warning about returning address of local variable or temporary

std::reverse_iterator::operator*() returns by reference while
QKeyValueIterator::operator*() returns by value, so MSVC is correct
when it warns about returning the address of a local variable or
temporary in (*itStop).second:

C:\Program Files\Microsoft Visual Studio\2022\Enterprise\VC\Tools\MSVC\14.30.30705\include\xutility(1582) : error C2220: the following warning is treated as an error
C:\Program Files\Microsoft Visual Studio\2022\Enterprise\VC\Tools\MSVC\14.30.30705\include\xutility(1582) : warning C4172: returning address of local variable or temporary

Avoid this by just iterating backwards.

Amends 6ed8a22dd2756557954dc85052870c0894de06ba.

Change-Id: I01ce7cb151efa61e8702686b3a463790869df72c
Reviewed-by: Marc Mutz <marc.mutz@qt.io>
Reviewed-by: Giuseppe D'Angelo <giuseppe.dangelo@kdab.com>
(cherry picked from commit a9084297f629423c64d571d7f7286d3c0e239247)
Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>

1 files changed, 2 insertions, 7 deletions

diff --git a/src/shared/qtgradienteditor/qtgradientstopsmodel.cpp b/src/shared/qtgradienteditor/qtgradientstopsmodel.cpp
index cd587793e..c064eeff4 100644
--- a/src/shared/qtgradienteditor/qtgradientstopsmodel.cpp
+++ b/src/shared/qtgradienteditor/qtgradientstopsmodel.cpp
@@ -418,17 +418,12 @@ void QtGradientStopsModel::clearSelection()
         selectStop(stop, false);
 }
 
-namespace {
-    template <typename BidirectionalIterator>
-    std::reverse_iterator<BidirectionalIterator> rev(BidirectionalIterator it)
-    { return std::reverse_iterator<BidirectionalIterator>(it); }
-}
-
 void QtGradientStopsModel::flipAll()
 {
     QMap<qreal, QtGradientStop *> stopsMap = stops();
     QMap<QtGradientStop *, bool> swappedList;
-    for (auto itStop = rev(stopsMap.keyValueEnd()), end = rev(stopsMap.keyValueBegin()); itStop != end; ++itStop) {
+    for (auto itStop = stopsMap.keyValueEnd(), begin = stopsMap.keyValueBegin(); itStop != begin;) {
+        --itStop;
         QtGradientStop *stop = (*itStop).second;
         if (swappedList.contains(stop))
             continue;