Avoid deleting QtWebComboBox it's own nested QEventLoop

A race condition meant that sometimes a QtWebComboBox would be deleted
in an eventloop run while hiding itself. This patch adds a flags
and delays scheduling a deletion until after the nested eventloop.

Task-number: QTBUG-29844
Change-Id: Ia5e03954756afa29c0be0a2d7f49ae8d1dbba250
Reviewed-by: Michael Bruning <michael.bruning@digia.com>

3 files changed, 28 insertions, 2 deletions

diff --git a/Source/WebKit/qt/WidgetSupport/QtFallbackWebPopup.cpp b/Source/WebKit/qt/WidgetSupport/QtFallbackWebPopup.cpp
index 5bf90d800..61ddacaa8 100644
--- a/Source/WebKit/qt/WidgetSupport/QtFallbackWebPopup.cpp
+++ b/Source/WebKit/qt/WidgetSupport/QtFallbackWebPopup.cpp
@@ -128,7 +128,7 @@ void QtFallbackWebPopup::deleteComboBox()
 {
     if (!m_combo)
         return;
-    m_combo->deleteLater();
+    m_combo->deleteComboBox();
     m_combo = 0;
 }
 
diff --git a/Source/WebKit/qt/WidgetSupport/QtWebComboBox.cpp b/Source/WebKit/qt/WidgetSupport/QtWebComboBox.cpp
index 2c22cd476..4cfa366dc 100644
--- a/Source/WebKit/qt/WidgetSupport/QtWebComboBox.cpp
+++ b/Source/WebKit/qt/WidgetSupport/QtWebComboBox.cpp
@@ -31,7 +31,7 @@
 namespace WebCore {
 
 QtWebComboBox::QtWebComboBox()
-    : QComboBox()
+    : QComboBox(), m_hiding(false), m_deleteAfterHiding(false)
 {
     // Install an event filter on the view inside the combo box popup to make sure we know
     // when the popup got closed. E.g. QComboBox::hidePopup() won't be called when the popup
@@ -53,6 +53,25 @@ bool QtWebComboBox::eventFilter(QObject* watched, QEvent* event)
     return false;
 }
 
+void QtWebComboBox::hidePopup()
+{
+    m_hiding = true;
+    // QComboBox::hidePopup() runs an eventloop, we need to make sure we do not delete ourselves in that loop.
+    QComboBox::hidePopup();
+    m_hiding = false;
+    if (m_deleteAfterHiding)
+        deleteLater();
+}
+
+
+void QtWebComboBox::deleteComboBox()
+{
+    if (!m_hiding)
+        deleteLater();
+    else
+        m_deleteAfterHiding = true;
 }
 
+} // namespace
+
 #endif // QT_NO_COMBOBOX
diff --git a/Source/WebKit/qt/WidgetSupport/QtWebComboBox.h b/Source/WebKit/qt/WidgetSupport/QtWebComboBox.h
index e32427edf..90b617b3d 100644
--- a/Source/WebKit/qt/WidgetSupport/QtWebComboBox.h
+++ b/Source/WebKit/qt/WidgetSupport/QtWebComboBox.h
@@ -36,8 +36,15 @@ public:
     void showPopupAtCursorPosition();
     virtual bool eventFilter(QObject* watched, QEvent*);
 
+    virtual void hidePopup() OVERRIDE;
+    void deleteComboBox();
+
 Q_SIGNALS:
     void didHide();
+
+private:
+    bool m_hiding;
+    bool m_deleteAfterHiding;
 };
 
 }