Projectexplorer: Delay querying for folder icon.

As a custom icon is set in most cases anyway.

Reviewed-by: Robert Loehning <robert.loehning@nokia.com>

src/plugins/projectexplorer/projectnodes.cpp

@@ -154,8 +154,7 @@ bool FileNode::isGenerated() const
 */
 FolderNode::FolderNode(const QString &folderPath)  :
     Node(FolderNodeType, folderPath),
-    m_displayName(QDir::toNativeSeparators(folderPath)),
-    m_icon(Core::FileIconProvider::instance()->icon(QFileIconProvider::Folder))
+    m_displayName(QDir::toNativeSeparators(folderPath))
 {
 }
 
@@ -182,6 +181,9 @@ QString FolderNode::displayName() const
  */
 QIcon FolderNode::icon() const
 {
+    // Instantiating the Icon provider is expensive.
+    if (m_icon.isNull())
+        m_icon = Core::FileIconProvider::instance()->icon(QFileIconProvider::Folder);
     return m_icon;
 }
 

src/plugins/projectexplorer/projectnodes.h

@@ -147,7 +147,7 @@ private:
     // managed by ProjectNode
     friend class ProjectNode;
     QString m_displayName;
-    QIcon m_icon;
+    mutable QIcon m_icon;
 };
 
 class PROJECTEXPLORER_EXPORT ProjectNode : public FolderNode