Revamp tracker list widget

Internally redesign tracker list widget using Qt Model/View architecture.
Make tracker list sortable by any column.

PR #19633.
Closes #261.

src/gui/trackerlist/trackerlistitemdelegate.cpp

@@ -0,0 +1,65 @@
+/*
+ * Bittorrent Client using Qt and libtorrent.
+ * Copyright (C) 2023  Vladimir Golovnev <glassez@yandex.ru>
+ *
+ * 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.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
+ *
+ * In addition, as a special exception, the copyright holders give permission to
+ * link this program with the OpenSSL project's "OpenSSL" library (or with
+ * modified versions of it that use the same license as the "OpenSSL" library),
+ * and distribute the linked executables. You must obey the GNU General Public
+ * License in all respects for all of the code used other than "OpenSSL".  If you
+ * modify file(s), you may extend this exception to your version of the file(s),
+ * but you are not obligated to do so. If you do not wish to do so, delete this
+ * exception statement from your version.
+ */
+
+#include "trackerlistitemdelegate.h"
+
+#include <QModelIndex>
+#include <QPainter>
+
+#include "trackerlistmodel.h"
+#include "trackerlistwidget.h"
+
+TrackerListItemDelegate::TrackerListItemDelegate(TrackerListWidget *view)
+    : QStyledItemDelegate(view)
+    , m_view {view}
+{
+    Q_ASSERT(m_view);
+}
+
+void TrackerListItemDelegate::initStyleOption(QStyleOptionViewItem *option, const QModelIndex &index) const
+{
+    QStyledItemDelegate::initStyleOption(option, index);
+
+    if (index.parent().isValid() || !m_view->isExpanded(index.siblingAtColumn(0)))
+        return;
+
+    switch (index.column())
+    {
+    case TrackerListModel::COL_PEERS:
+    case TrackerListModel::COL_SEEDS:
+    case TrackerListModel::COL_LEECHES:
+    case TrackerListModel::COL_TIMES_DOWNLOADED:
+    case TrackerListModel::COL_MSG:
+    case TrackerListModel::COL_NEXT_ANNOUNCE:
+    case TrackerListModel::COL_MIN_ANNOUNCE:
+        option->text.clear();
+        break;
+    default:
+        break;
+    }
+}