Work around memory leak issue in grid and linear layouts.

These classes create a new QWidget and assign it to a static pointer
which is never cleaned up. Using Q_GLOBAL_STATIC ensures that they are
deleted on library unload. This is really just a cosmetic change that
removes a leak warning - the real fix should be to find a way to not
use a new QWidget like this. It seems odd that QGraphicsLayouts, which
don't use QWidget in any other way, should depend on QWidget like this.

Task-number: QTBUG-10768

Merge-request: 741
Reviewed-by: Jan-Arve Sæther <jan-arve.saether@nokia.com>
(cherry picked from commit ea6a5146397b668bf535ee7249bd4262d6185234)

2 files changed, 6 insertions, 8 deletions

diff --git a/src/gui/graphicsview/qgraphicsgridlayout.cpp b/src/gui/graphicsview/qgraphicsgridlayout.cpp
index 83db3ec..062b5ac 100644
--- a/src/gui/graphicsview/qgraphicsgridlayout.cpp
+++ b/src/gui/graphicsview/qgraphicsgridlayout.cpp
@@ -94,14 +94,13 @@ public:
 #endif
 };
 
+Q_GLOBAL_STATIC(QWidget, globalStyleInfoWidget);
+
 QLayoutStyleInfo QGraphicsGridLayoutPrivate::styleInfo() const
 {
-    static QWidget *wid = 0;
-    if (!wid)
-        wid = new QWidget;
     QGraphicsItem *item = parentItem();
     QStyle *style = (item && item->isWidget()) ? static_cast<QGraphicsWidget*>(item)->style() : QApplication::style();
-    return QLayoutStyleInfo(style, wid);
+    return QLayoutStyleInfo(style, globalStyleInfoWidget());
 }
 
 /*!
diff --git a/src/gui/graphicsview/qgraphicslinearlayout.cpp b/src/gui/graphicsview/qgraphicslinearlayout.cpp
index b828722..37408ef 100644
--- a/src/gui/graphicsview/qgraphicslinearlayout.cpp
+++ b/src/gui/graphicsview/qgraphicslinearlayout.cpp
@@ -171,14 +171,13 @@ int QGraphicsLinearLayoutPrivate::gridColumn(int index) const
     return int(qMin(uint(index), uint(engine.columnCount())));
 }
 
+Q_GLOBAL_STATIC(QWidget, globalStyleInfoWidget)
+
 QLayoutStyleInfo QGraphicsLinearLayoutPrivate::styleInfo() const
 {
-    static QWidget *wid = 0;
-    if (!wid)
-        wid = new QWidget;
     QGraphicsItem *item = parentItem();
     QStyle *style = (item && item->isWidget()) ? static_cast<QGraphicsWidget*>(item)->style() : QApplication::style();
-    return QLayoutStyleInfo(style, wid);
+    return QLayoutStyleInfo(style, globalStyleInfoWidget());
 }
 
 /*!