Fix a bug that got revealed by 604c51f1fc5c79b7fad12cda911b06b9e6e5005f

The bug has been around for a while, but change 604c51f1fc5c7 made it
emerge.
The problem was that stretches were combined by always *maxing* them.
The values of 'stretch' can be interpreted as this:

-1: (the default) it means that the items should be stretched with
    the stretch factor dervived from the size hints. (In practice this
    means that they are distributed fairly).
 0: Means that the item should not be stretched
>0: Means that the item should be stretch with that number as a factor.

This meant that combining one item with a fixed size(0) and another
item with a default stretch (-1) the combined row stretch would end
up being fixed.

This also fixes how stretches are combined for spanning items too.

Task-number: QTBUG-13551
Reviewed-by: John Tapsell
(cherry picked from commit 7fbf1829e11504eca6a55f1e5dbddf2f658b5302)

1 files changed, 3 insertions, 2 deletions

diff --git a/src/gui/graphicsview/qgridlayoutengine.cpp b/src/gui/graphicsview/qgridlayoutengine.cpp
index 8f833f8..cd30dfb 100644
--- a/src/gui/graphicsview/qgridlayoutengine.cpp
+++ b/src/gui/graphicsview/qgridlayoutengine.cpp
@@ -194,7 +194,8 @@ void QGridLayoutRowData::distributeMultiCells(const QGridLayoutRowInfo &rowInfo)
 
         for (int k = 0; k < span; ++k) {
             boxes[start + k].combine(extras[k]);
-            stretches[start + k] = qMax(stretches[start + k], stretch);
+            if (stretch != 0)
+                stretches[start + k] = qMax(stretches[start + k], stretch);
         }
     }
     multiCellMap.clear();
@@ -1472,7 +1473,7 @@ void QGridLayoutEngine::fillRowData(QGridLayoutRowData *rowData, const QLayoutSt
                     QGridLayoutBox *box;
                     if (effectiveRowSpan == 1) {
                         box = &rowBox;
-                        if (!userRowStretch)
+                        if (!userRowStretch && itemStretch != 0)
                             rowStretch = qMax(rowStretch, itemStretch);
                     } else {
                         QGridLayoutMultiCellData &multiCell =