Item views: fix regression causing unexpected widget overlapping

A certain geometry adjustment was (practically) introduced in Qt 5.11,
and caused very surprising behavior, where item widgets will often
overwrite neighbouring cells. This has resulted in a number of bug
reports. Since the adjustment has such serious side effects, and does
not seem to be relevant any longer for the issue for which it was
intended, remove it here.

More details: From early Qt 4 times, QStyledItemDelegate would do some
automatic expansion of the geometry of editor widgets - but only if
the layout was RightToLeft. Hence, the effect of it was rarely
seen. QTBUG-37433 did, for Qt 5.10, and complained about it. However,
the resulting code change did not remove the adjustment, but instead
extended it to apply to the normal LeftToRight layout also. Hence,
more users experienced it, and reported it as a regression.

Also, now in Qt 5.13, it seems Qt has changed in other ways, and the
geometry adjustment no longer seems to help (or indeed make any
difference to) the original case in QTBUG-37433.

Fixes: QTBUG-78495
Fixes: QTBUG-76011
Fixes: QTBUG-68476
Change-Id: I4a4e873969eb1d89843f98fc63d90371207515d1
Reviewed-by: Paul Olav Tvete <[email protected]>

src/widgets/itemviews/qstyleditemdelegate.cpp

@@ -514,15 +514,6 @@ void QStyledItemDelegate::updateEditorGeometry(QWidget *editor,
 
     QStyle *style = widget ? widget->style() : QApplication::style();
     QRect geom = style->subElementRect(QStyle::SE_ItemViewItemText, &opt, widget);
-    const int delta = qSmartMinSize(editor).width() - geom.width();
-    if (delta > 0) {
-        //we need to widen the geometry
-        if (editor->layoutDirection() == Qt::RightToLeft)
-            geom.adjust(-delta, 0, 0, 0);
-        else
-            geom.adjust(0, 0, delta, 0);
-    }
-
     editor->setGeometry(geom);
 }