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.cpp

@@ -0,0 +1,212 @@
+/**************************************************************************
+**
+** 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.
+**
+**************************************************************************/
+
+#include "filesystemwatcher.h"
+
+#include <QtCore/QDebug>
+#include <QtCore/QDir>
+#include <QtCore/QFileInfo>
+#include <QtCore/QFileSystemWatcher>
+#include <QtCore/QTimer>
+
+enum { debug = false };
+
+namespace QmlProjectManager {
+
+int FileSystemWatcher::m_objectCount = 0;
+QHash<QString,int> FileSystemWatcher::m_fileCount;
+QHash<QString,int> FileSystemWatcher::m_directoryCount;
+QFileSystemWatcher *FileSystemWatcher::m_watcher = 0;
+
+FileSystemWatcher::FileSystemWatcher(QObject *parent) :
+    QObject(parent)
+{
+    if (!m_watcher)
+        m_watcher = new QFileSystemWatcher();
+    ++m_objectCount;
+    connect(m_watcher, SIGNAL(fileChanged(QString)),
+            this, SLOT(slotFileChanged(QString)));
+    connect(m_watcher, SIGNAL(directoryChanged(QString)),
+            this, SLOT(slotDirectoryChanged(QString)));
+}
+
+FileSystemWatcher::~FileSystemWatcher()
+{
+    removeFiles(files());
+    removeDirectories(directories());
+
+    if (--m_objectCount == 0) {
+        delete m_watcher;
+        m_watcher = 0;
+    }
+}
+
+void FileSystemWatcher::addFile(const QString &file)
+{
+    addFiles(QStringList(file));
+}
+
+void FileSystemWatcher::addFiles(const QStringList &files)
+{
+    QStringList toAdd;
+
+    if (debug)
+        qDebug() << Q_FUNC_INFO << files.count();
+
+    foreach (const QString &file, files) {
+        if (m_files.contains(file)) {
+            qWarning() << "FileSystemWatcher: File" << file << "is already being watched";
+            continue;
+        }
+        m_files.append(file);
+
+        const int count = ++m_fileCount[file];
+        Q_ASSERT(count > 0);
+
+        if (count == 1)
+            toAdd << file;
+    }
+
+    if (!toAdd.isEmpty())
+        m_watcher->addPaths(toAdd);
+}
+
+void FileSystemWatcher::removeFile(const QString &file)
+{
+    removeFiles(QStringList(file));
+}
+
+void FileSystemWatcher::removeFiles(const QStringList &files)
+{
+    QStringList toRemove;
+
+    if (debug)
+        qDebug() << Q_FUNC_INFO << files.count();
+
+    foreach (const QString &file, files) {
+        if (!m_files.contains(file)) {
+            qWarning() << "FileSystemWatcher: File" << file << "is not watched";
+            continue;
+        }
+        m_files.removeOne(file);
+        const int count = --m_fileCount[file];
+        Q_ASSERT(count >= 0);
+
+        if (!count) {
+            toRemove << file;
+        }
+    }
+
+    if (!toRemove.isEmpty())
+        m_watcher->removePaths(toRemove);
+}
+
+QStringList FileSystemWatcher::files() const
+{
+    return m_files;
+}
+
+void FileSystemWatcher::addDirectory(const QString &directory)
+{
+    addDirectories(QStringList(directory));
+}
+
+void FileSystemWatcher::addDirectories(const QStringList &directories)
+{
+    QStringList toAdd;
+
+    if (debug)
+        qDebug() << Q_FUNC_INFO << directories.count();
+
+    foreach (const QString &directory, directories) {
+        if (m_directories.contains(directory)) {
+            qWarning() << "Directory" << directory << "is already being watched";
+            continue;
+        }
+        m_directories.append(directory);
+
+        const int count = ++m_directoryCount[directory];
+        Q_ASSERT(count > 0);
+
+        if (count == 1)
+            toAdd << directory;
+    }
+
+    if (!toAdd.isEmpty())
+        m_watcher->addPaths(toAdd);
+}
+
+void FileSystemWatcher::removeDirectory(const QString &directory)
+{
+    removeDirectories(QStringList(directory));
+}
+
+void FileSystemWatcher::removeDirectories(const QStringList &directories)
+{
+    QStringList toRemove;
+
+    if (debug)
+        qDebug() << Q_FUNC_INFO << directories.count();
+
+    foreach (const QString &directory, directories) {
+        if (!m_directories.contains(directory)) {
+            qWarning() << "FileSystemWatcher: Directory" << directory << "is not watched";
+            continue;
+        }
+        m_directories.removeOne(directory);
+
+        const int count = --m_directoryCount[directory];
+        Q_ASSERT(count >= 0);
+
+        if (!count) {
+            toRemove << directory;
+        }
+    }
+    if (!toRemove.isEmpty())
+        m_watcher->removePaths(toRemove);
+}
+
+QStringList FileSystemWatcher::directories() const
+{
+    return m_directories;
+}
+
+void FileSystemWatcher::slotFileChanged(const QString &path)
+{
+    if (m_files.contains(path))
+        emit fileChanged(path);
+}
+
+void FileSystemWatcher::slotDirectoryChanged(const QString &path)
+{
+    if (m_directories.contains(path))
+        emit directoryChanged(path);
+}
+
+} // namespace QmlProjectManager