Fix potential endless loop in layout

Usecase:
- No scrollbar is shown
- Window size will be decreased so that a scrollbar gets necessary

The decreased window size minus the space required for the scrollbar
results in a relayout of the items. In 99 % of all
cases a decreased window size won't result in showing more items in parallel in
comparison to a larger window size. However in the remaining 1 % this can
happen (e.g. see bug 293318 for a sample). This results in an endless loop as
now no scrollbar is required anymore, the layout changes again, the scrollbar
is required again, ...

BUG: 293318
FIXED-IN: 4.8.1

1 files changed, 13 insertions, 0 deletions

diff --git a/src/kitemviews/kitemlistview.cpp b/src/kitemviews/kitemlistview.cpp
index c671a2e6e..52d857705 100644
--- a/src/kitemviews/kitemlistview.cpp
+++ b/src/kitemviews/kitemlistview.cpp
@@ -1880,6 +1880,19 @@ bool KItemListView::animateChangedItemCount(int changedItemCount) const
     return changedItemCount <= maximum * 2 / 3;
 }
 
+
+bool KItemListView::scrollBarRequired(const QSizeF& size) const
+{
+    const QSizeF oldSize = m_layouter->size();
+
+    m_layouter->setSize(size);
+    const qreal maxOffset = m_layouter->maximumScrollOffset();
+    m_layouter->setSize(oldSize);
+
+    return m_layouter->scrollOrientation() == Qt::Vertical ? maxOffset > size.height()
+                                                           : maxOffset > size.width();
+}
+
 int KItemListView::calculateAutoScrollingIncrement(int pos, int range, int oldInc)
 {
     int inc = 0;