QmlProjectFiles: Dramatically reduce number of watched fs entities

Only watch directories, and not single files. Also, share one
FileSystemWatcher between projects & FileFilter items.

This fixes the issue that the process runs out of file handles e.g.
when loading a .qmlproject file containing all of qt examples & demos.

Basic implementation of FileSystemWatcher was copied from
ProjectExplorer::FileWatcher - however the FileWatcher is only
for files (and not directories), and also monitors the last
change date etc.

src/plugins/qmlprojectmanager/fileformat/filesystemwatcher.h

@@ -0,0 +1,88 @@
+/**************************************************************************
+**
+** This file is part of Qt Creator
+**
+** Copyright (c) 2010 Nokia Corporation and/or its subsidiary(-ies).
+**
+** Contact: Nokia Corporation (qt-info@nokia.com)
+**
+** Commercial Usage
+**
+** Licensees holding valid Qt Commercial licenses may use this file in
+** accordance with the Qt Commercial License Agreement provided with the
+** Software or, alternatively, in accordance with the terms contained in
+** a written agreement between you and Nokia.
+**
+** GNU Lesser General Public License Usage
+**
+** Alternatively, this file may be used under the terms of the GNU Lesser
+** General Public License version 2.1 as published by the Free Software
+** Foundation and appearing in the file LICENSE.LGPL included in the
+** packaging of this file.  Please review the following information to
+** ensure the GNU Lesser General Public License version 2.1 requirements
+** will be met: http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html.
+**
+** If you are unsure which license is appropriate for your use, please
+** contact the sales department at http://qt.nokia.com/contact.
+**
+**************************************************************************/
+
+#ifndef FSWATCHER_H
+#define FSWATCHER_H
+
+#include <QtCore/QDateTime>
+#include <QtCore/QHash>
+#include <QtCore/QObject>
+#include <QtCore/QStringList>
+#include <QtCore/QMap>
+
+class QTimer;
+class QFileSystemWatcher;
+
+namespace QmlProjectManager {
+
+class FileSystemWatcher : public QObject
+{
+    Q_DISABLE_COPY(FileSystemWatcher)
+    Q_OBJECT
+public:
+    explicit FileSystemWatcher(QObject *parent = 0);
+    virtual ~FileSystemWatcher();
+
+    void addFile(const QString &file);
+    void addFiles(const QStringList &files);
+
+    void removeFile(const QString &file);
+    void removeFiles(const QStringList &files);
+
+    QStringList files() const;
+
+    void addDirectory(const QString &file);
+    void addDirectories(const QStringList &files);
+
+    void removeDirectory(const QString &file);
+    void removeDirectories(const QStringList &files);
+
+    QStringList directories() const;
+
+private slots:
+    void slotFileChanged(const QString &path);
+    void slotDirectoryChanged(const QString &path);
+
+signals:
+    void fileChanged(const QString &path);
+    void directoryChanged(const QString &path);
+
+private:
+    QStringList m_files;
+    QStringList m_directories;
+
+    static int m_objectCount;
+    static QHash<QString, int> m_fileCount;
+    static QHash<QString, int> m_directoryCount;
+    static QFileSystemWatcher *m_watcher;
+};
+
+} // namespace QmlProjectManager
+
+#endif // FSWATCHER_H