Fixed QLayout::addChildLayout(QLayout *l) when l had a parent

Previously if l had a parent, addChildLayout would warn and skip the
reparenting, but it would still add the sub layout to the layout.
This caused some inconsistencies in the hierarchy which in worst case
could cause crashes.

Task-number: QTBUG-30758
(cherry-picked from qtbase commit 146658a10f290603470b800d71b778239e764312)
Change-Id: Iee6ace3189620395d7670007a23783823ed616b9
Reviewed-by: Paul Olav Tvete <paul.tvete@digia.com>

5 files changed, 19 insertions, 5 deletions

diff --git a/src/gui/kernel/qboxlayout.cpp b/src/gui/kernel/qboxlayout.cpp
index 91393ed..444cea2 100644
--- a/src/gui/kernel/qboxlayout.cpp
+++ b/src/gui/kernel/qboxlayout.cpp
@@ -1001,7 +1001,8 @@ void QBoxLayout::insertSpacerItem(int index, QSpacerItem *spacerItem)
 void QBoxLayout::insertLayout(int index, QLayout *layout, int stretch)
 {
     Q_D(QBoxLayout);
-    addChildLayout(layout);
+    if (!adoptLayout(layout))
+        return;
     if (index < 0)                                // append
         index = d->list.count();
     QBoxLayoutItem *it = new QBoxLayoutItem(layout, stretch);
diff --git a/src/gui/kernel/qformlayout.cpp b/src/gui/kernel/qformlayout.cpp
index ba88211..8f97d1c 100644
--- a/src/gui/kernel/qformlayout.cpp
+++ b/src/gui/kernel/qformlayout.cpp
@@ -976,8 +976,8 @@ void QFormLayoutPrivate::setLayout(int row, QFormLayout::ItemRole role, QLayout
 {
     if (layout) {
         Q_Q(QFormLayout);
-        q->addChildLayout(layout);
-        setItem(row, role, layout);
+        if (q->adoptLayout(layout))
+            setItem(row, role, layout);
     }
 }
 
diff --git a/src/gui/kernel/qgridlayout.cpp b/src/gui/kernel/qgridlayout.cpp
index c9550de..731d5cd9 100644
--- a/src/gui/kernel/qgridlayout.cpp
+++ b/src/gui/kernel/qgridlayout.cpp
@@ -1609,7 +1609,8 @@ void QGridLayout::addWidget(QWidget *widget, int fromRow, int fromColumn,
 void QGridLayout::addLayout(QLayout *layout, int row, int column, Qt::Alignment alignment)
 {
     Q_D(QGridLayout);
-    addChildLayout(layout);
+    if (!adoptLayout(layout))
+        return;
     QGridBox *b = new QGridBox(layout);
     b->setAlignment(alignment);
     d->add(b, row, column);
@@ -1628,7 +1629,8 @@ void QGridLayout::addLayout(QLayout *layout, int row, int column,
                                       int rowSpan, int columnSpan, Qt::Alignment alignment)
 {
     Q_D(QGridLayout);
-    addChildLayout(layout);
+    if (!adoptLayout(layout))
+        return;
     QGridBox *b = new QGridBox(layout);
     b->setAlignment(alignment);
     d->add(b, row, (rowSpan < 0) ? -1 : row + rowSpan - 1, column, (columnSpan < 0) ? -1 : column + columnSpan - 1);
diff --git a/src/gui/kernel/qlayout.cpp b/src/gui/kernel/qlayout.cpp
index 1f7b34c..ce8322b 100644
--- a/src/gui/kernel/qlayout.cpp
+++ b/src/gui/kernel/qlayout.cpp
@@ -935,6 +935,16 @@ void QLayout::addChildLayout(QLayout *l)
 
 }
 
+/*!
+   \internal
+ */
+bool QLayout::adoptLayout(QLayout *layout)
+{
+    const bool ok = !layout->parent();
+    addChildLayout(layout);
+    return ok;
+}
+
 #ifdef QT_DEBUG
 static bool layoutDebug()
 {
diff --git a/src/gui/kernel/qlayout.h b/src/gui/kernel/qlayout.h
index d4a79d9..09f0e33 100644
--- a/src/gui/kernel/qlayout.h
+++ b/src/gui/kernel/qlayout.h
@@ -189,6 +189,7 @@ protected:
     void childEvent(QChildEvent *e);
     void addChildLayout(QLayout *l);
     void addChildWidget(QWidget *w);
+    bool adoptLayout(QLayout *layout);
 #ifdef QT3_SUPPORT
     QT3_SUPPORT void deleteAllItems();
 #endif