annotate src/fswatcher.cpp @ 571:012ba1b83328

Show cancel button with progress bar only when running an operation that it makes sense to cancel (we don't really want people cancelling e.g. initial folder scan because it would leave things in an inconsistent state)

/* -*- c-basic-offset: 4 indent-tabs-mode: nil -*-  vi:set ts=8 sts=4 sw=4: */

/*
    EasyMercurial

    Based on hgExplorer by Jari Korhonen
    Copyright (c) 2010 Jari Korhonen
    Copyright (c) 2012 Chris Cannam
    Copyright (c) 2012 Queen Mary, University of London
    
    This program is free software; you can redistribute it and/or
    modify it under the terms of the GNU General Public License as
    published by the Free Software Foundation; either version 2 of the
    License, or (at your option) any later version.  See the file
    COPYING included with this distribution for more information.
*/

#include "fswatcher.h"
#include "debug.h"

#include <QMutexLocker>
#include <QDir>

#include <deque>

//#define DEBUG_FSWATCHER 1

/*
 * Watching the filesystem is trickier than it seems at first glance.
 *
 * We ideally should watch every directory, and every file that is
 * tracked by Hg. If a new file is created in a directory, then we
 * need to respond in order to show it as a potential candidate to be
 * added.
 *
 * Complicating matters though is that Hg itself might modify the
 * filesystem. This can happen even in "read-only" operations: for
 * example, hg stat creates files called hg-checklink and hg-checkexec
 * to test properties of the filesystem. So we need to know to ignore
 * those files; unfortunately, when watching a directory (which is how
 * we find out about the creation of new files) we are notified only
 * that the directory has changed -- we aren't told what changed.
 *
 * This means that, when a directory changes, we need to rescan the
 * directory to learn whether the set of files in it _excluding_ files
 * matching our ignore patterns differs from the previous scan, and
 * ignore the change if it doesn't.
 */

FsWatcher::FsWatcher() :
    m_lastToken(0),
    m_lastCounter(0)
{
    connect(&m_watcher, SIGNAL(directoryChanged(QString)),
	    this, SLOT(fsDirectoryChanged(QString)));
    connect(&m_watcher, SIGNAL(fileChanged(QString)),
	    this, SLOT(fsFileChanged(QString)));
}

FsWatcher::~FsWatcher()
{
}

void
FsWatcher::setWorkDirPath(QString path)
{
    QMutexLocker locker(&m_mutex);
    if (m_workDirPath == path) return;
    // annoyingly, removePaths prints a warning if given an empty list
    if (!m_watcher.directories().empty()) {
        m_watcher.removePaths(m_watcher.directories());
    }
    if (!m_watcher.files().empty()) {
        m_watcher.removePaths(m_watcher.files());
    }
    m_workDirPath = path;
    addWorkDirectory(path);
    debugPrint();
}

void
FsWatcher::setTrackedFilePaths(QStringList paths)
{
    QMutexLocker locker(&m_mutex);

    QSet<QString> alreadyWatched = 
	QSet<QString>::fromList(m_watcher.files());

    foreach (QString path, paths) {
        path = m_workDirPath + QDir::separator() + path;
        if (!alreadyWatched.contains(path)) {
            m_watcher.addPath(path);
        } else {
            alreadyWatched.remove(path);
        }
    }

    // Remove the remaining paths, those that were being watched
    // before but that are not in the list we were given
    foreach (QString path, alreadyWatched) {
        m_watcher.removePath(path);
    }

    debugPrint();
}

void
FsWatcher::addWorkDirectory(QString path)
{
    // QFileSystemWatcher will refuse to add a file or directory to
    // its watch list that it is already watching -- fine -- but it
    // prints a warning when this happens, which we wouldn't want.  So
    // we'll check for duplicates ourselves.
    QSet<QString> alreadyWatched = 
	QSet<QString>::fromList(m_watcher.directories());
    
    std::deque<QString> pending;
    pending.push_back(path);

    while (!pending.empty()) {

        QString path = pending.front();
        pending.pop_front();
        if (!alreadyWatched.contains(path)) {
            m_watcher.addPath(path);
            m_dirContents[path] = scanDirectory(path);
        }

        QDir d(path);
        if (d.exists()) {
            d.setFilter(QDir::Dirs | QDir::NoDotAndDotDot |
                        QDir::Readable | QDir::NoSymLinks);
            foreach (QString entry, d.entryList()) {
                if (entry.startsWith('.')) continue;
                QString entryPath = d.absoluteFilePath(entry);
                pending.push_back(entryPath);
            }
        }
    }
}

void
FsWatcher::setIgnoredFilePrefixes(QStringList prefixes)
{
    QMutexLocker locker(&m_mutex);
    m_ignoredPrefixes = prefixes;
}

void
FsWatcher::setIgnoredFileSuffixes(QStringList suffixes)
{
    QMutexLocker locker(&m_mutex);
    m_ignoredSuffixes = suffixes;
}

int
FsWatcher::getNewToken()
{
    QMutexLocker locker(&m_mutex);
    int token = ++m_lastToken;
    m_tokenMap[token] = m_lastCounter;
    return token;
}

QSet<QString>
FsWatcher::getChangedPaths(int token)
{
    QMutexLocker locker(&m_mutex);
    size_t lastUpdatedAt = m_tokenMap[token];
    QSet<QString> changed;
    for (QHash<QString, size_t>::const_iterator i = m_changes.begin();
	 i != m_changes.end(); ++i) {
	if (i.value() > lastUpdatedAt) {
	    changed.insert(i.key());
	}
    }
    m_tokenMap[token] = m_lastCounter;
    return changed;
}

void
FsWatcher::fsDirectoryChanged(QString path)
{
    {
	QMutexLocker locker(&m_mutex);

	if (shouldIgnore(path)) return;

        QSet<QString> files = scanDirectory(path);
        if (files == m_dirContents[path]) {
#ifdef DEBUG_FSWATCHER
            std::cerr << "FsWatcher: Directory " << path << " has changed, but not in a way that we are monitoring" << std::endl;
#endif
            return;
        } else {
#ifdef DEBUG_FSWATCHER
            std::cerr << "FsWatcher: Directory " << path << " has changed" << std::endl;
#endif
            m_dirContents[path] = files;
        }

        size_t counter = ++m_lastCounter;
        m_changes[path] = counter;
    }

    emit changed();
}

void
FsWatcher::fsFileChanged(QString path)
{
    {
        QMutexLocker locker(&m_mutex);

        // We don't check whether the file matches an ignore pattern,
        // because we are only notified for file changes if we are
        // watching the file explicitly, i.e. the file is in the
        // tracked file paths list. So we never want to ignore them

#ifdef DEBUG_FSWATCHER
        std::cerr << "FsWatcher: Tracked file " << path << " has changed" << std::endl;
#endif

        size_t counter = ++m_lastCounter;
        m_changes[path] = counter;
    }

    emit changed();
}

bool
FsWatcher::shouldIgnore(QString path)
{
    QFileInfo fi(path);
    QString fn(fi.fileName());
    foreach (QString pfx, m_ignoredPrefixes) {
        if (fn.startsWith(pfx)) {
#ifdef DEBUG_FSWATCHER
            std::cerr << "(ignoring: " << path << ")" << std::endl;
#endif
            return true;
        }
    }
    foreach (QString sfx, m_ignoredSuffixes) {
        if (fn.endsWith(sfx)) {
#ifdef DEBUG_FSWATCHER
            std::cerr << "(ignoring: " << path << ")" << std::endl;
#endif
            return true;
        }
    }
    return false;
}

QSet<QString>
FsWatcher::scanDirectory(QString path)
{
    QSet<QString> files;
    QDir d(path);
    if (d.exists()) {
        d.setFilter(QDir::Files | QDir::NoDotAndDotDot |
                    QDir::Readable | QDir::NoSymLinks);
        foreach (QString entry, d.entryList()) {
            if (entry.startsWith('.')) continue;
            if (shouldIgnore(entry)) continue;
            files.insert(entry);
        }
    }
//    std::cerr << "scanDirectory:" << std::endl;
//    foreach (QString f, files) std::cerr << f << std::endl;
    return files;
}

void
FsWatcher::debugPrint()
{
#ifdef DEBUG_FSWATCHER
    std::cerr << "FsWatcher: Now watching " << m_watcher.directories().size()
              << " directories and " << m_watcher.files().size()
              << " files" << std::endl;
#endif
}