src/views/versioncontrol/pendingthreadsmaintainer.h

   1 /***************************************************************************
   2  *   Copyright (C) 2010 by Peter Penz <peter.penz19@gmail.com>             *
   3  *                                                                         *
   4  *   This program is free software; you can redistribute it and/or modify  *
   5  *   it under the terms of the GNU General Public License as published by  *
   6  *   the Free Software Foundation; either version 2 of the License, or     *
   7  *   (at your option) any later version.                                   *
   8  *                                                                         *
   9  *   This program is distributed in the hope that it will be useful,       *
  10  *   but WITHOUT ANY WARRANTY; without even the implied warranty of        *
  11  *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the         *
  12  *   GNU General Public License for more details.                          *
  13  *                                                                         *
  14  *   You should have received a copy of the GNU General Public License     *
  15  *   along with this program; if not, write to the                         *
  16  *   Free Software Foundation, Inc.,                                       *
  17  *   51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA            *
  18  ***************************************************************************/
  19
  20 #ifndef PENDINGTHREADSMAINTAINER_H
  21 #define PENDINGTHREADSMAINTAINER_H
  22
  23 #include <libdolphin_export.h>
  24
  25 #include <QObject>
  26
  27 class QTimer;
  28
  29 /**
  30  * TODO: Replace the PendingThreadMaintainer by a kind of
  31  *       VersionControlThreadFactory that is responsible for creating
  32  *       and deleting the threads. This would bypass the hack to poll
  33  *       for pending threads.
  34  *
  35  * If the creator of a thread gets deleted, although the thread is still
  36  * working, usually QThread::wait() is invoked. The drawback of this
  37  * approach is that the user interface gets blocked for an undefined amount
  38  * of time. If the thread does not contain references to the creator, the
  39  * deleting can be forwarded to the PendingThreadsMaintainer. In the following
  40  * example it is assumed, that m_thread will be 0, if it has been deleted by the
  41  * creator after receiving the signal QThread::finished():
  42  *
  43  * \code
  44  * ThreadCreator::~ThreadCreator()
  45  * {
  46  *     if (m_thread) {
  47  *         PendingThreadsMaintainer::instance().append(m_thread);
  48  *         m_thread = 0;
  49  *     }
  50  * }
  51  * \endcode
  52  *
  53  * The thread will get automatically deleted after it (or has already) been finished.
  54  *
  55  * Implementation note: Connecting to the signal QThread::finished() is
  56  * not sufficient, as it is possible that the thread has already emitted
  57  * the signal, but the signal has not been received yet by the thread creator.
  58  * Because of this a polling is done each 5 seconds to check, whether the
  59  * thread has been finished.
  60  */
  61 class LIBDOLPHINPRIVATE_EXPORT PendingThreadsMaintainer : public QObject
  62 {
  63     Q_OBJECT
  64
  65 public:
  66     static PendingThreadsMaintainer& instance();
  67     virtual ~PendingThreadsMaintainer();
  68
  69     /**
  70      * Appends the thread \p thread to the maintainer. The thread
  71      * will be deleted by the maintainer after it has been finished.
  72      */
  73     void append(QThread* thread);
  74
  75 protected:
  76     PendingThreadsMaintainer();
  77
  78 private slots:
  79     void cleanup();
  80
  81 private:
  82     QList<QThread*> m_threads;
  83     QTimer* m_timer;
  84
  85     friend class PendingThreadsMaintainerSingleton;
  86 };
  87
  88 #endif