registry: Allow to cancel current searches

When user types into the search box the previous search is canceled.
This improves the speed with which the results can be obtained.

Based on #460 plus cosmetic changes.
Related to #265, #523.

src/registry/cancellationtoken.cpp

@@ -0,0 +1,40 @@
+/****************************************************************************
+**
+** Copyright (C) 2015 Artur Spychaj
+** Contact: http://zealdocs.org/contact.html
+**
+** This file is part of Zeal.
+**
+** Zeal 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 3 of the License, or
+** (at your option) any later version.
+**
+** Zeal 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 Zeal. If not, see <http://www.gnu.org/licenses/>.
+**
+****************************************************************************/
+
+#include "cancellationtoken.h"
+
+using namespace Zeal;
+
+CancellationToken::CancellationToken()
+{
+    m_cancelled = QSharedPointer<bool>(new bool(false));
+}
+
+void CancellationToken::cancel()
+{
+    *m_cancelled = true;
+}
+
+bool CancellationToken::isCanceled() const
+{
+    return *m_cancelled;
+}

src/registry/cancellationtoken.h

@@ -0,0 +1,47 @@
+/****************************************************************************
+**
+** Copyright (C) 2015 Artur Spychaj
+** Contact: http://zealdocs.org/contact.html
+**
+** This file is part of Zeal.
+**
+** Zeal 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 3 of the License, or
+** (at your option) any later version.
+**
+** Zeal 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 Zeal. If not, see <http://www.gnu.org/licenses/>.
+**
+****************************************************************************/
+
+#ifndef CANCELLATIONTOKEN_H
+#define CANCELLATIONTOKEN_H
+
+#include <QSharedPointer>
+
+namespace Zeal {
+
+/// Token that stores whether cancel was called on it.
+/// In async code can be used to check if another thread called cancel.
+struct CancellationToken
+{
+public:
+    CancellationToken();
+    bool isCanceled() const;
+    void cancel();
+
+private:
+    QSharedPointer<bool> m_cancelled;
+};
+
+}
+
+Q_DECLARE_METATYPE(Zeal::CancellationToken)
+
+#endif // CANCELLATIONTOKEN_H

src/registry/docsetregistry.cpp

@@ -23,6 +23,7 @@
 
 #include "docsetregistry.h"
 
+#include "cancellationtoken.h"
 #include "searchresult.h"
 
 #include <QDir>
@@ -35,6 +36,7 @@ DocsetRegistry::DocsetRegistry(QObject *parent) :
     m_thread(new QThread(this))
 {
     // Register for use in signal connections.
+    qRegisterMetaType<CancellationToken>("CancellationToken");
     qRegisterMetaType<QList<Zeal::SearchResult>>("QList<SearchResult>");
 
     // FIXME: Only search should be performed in a separate thread
@@ -122,21 +124,21 @@ void DocsetRegistry::_addDocset(const QString &path)
     emit docsetAdded(name);
 }
 
-void DocsetRegistry::search(const QString &query)
+void DocsetRegistry::search(const QString &query, const CancellationToken &token)
 {
-    // Only invalidate queries
-    if (query.isEmpty())
-        return;
-
-    QMetaObject::invokeMethod(this, "_runQuery", Qt::QueuedConnection, Q_ARG(QString, query));
+    QMetaObject::invokeMethod(this, "_runQuery", Qt::QueuedConnection,
+                              Q_ARG(QString, query), Q_ARG(CancellationToken, token));
 }
 
-void DocsetRegistry::_runQuery(const QString &query)
+void DocsetRegistry::_runQuery(const QString &query, const CancellationToken &token)
 {
     QList<SearchResult> results;
 
-    for (Docset *docset : docsets())
+    for (Docset *docset : docsets()) {
+        if (token.isCanceled())
+            return;
         results << docset->search(query);
+    }
 
     std::sort(results.begin(), results.end());
 

src/registry/docsetregistry.h

@@ -32,6 +32,7 @@ class QThread;
 
 namespace Zeal {
 
+struct CancellationToken;
 struct SearchResult;
 
 class DocsetRegistry : public QObject
@@ -52,7 +53,8 @@ class DocsetRegistry : public QObject
     Docset *docset(int index) const;
     QList<Docset *> docsets() const;
 
-    void search(const QString &query);
+    void search(const QString &query, const CancellationToken &token);
+    const QList<SearchResult> &queryResults();
 
 public slots:
     void addDocset(const QString &path);
@@ -65,7 +67,7 @@ public slots:
 
 private slots:
     void _addDocset(const QString &path);
-    void _runQuery(const QString &query);
+    void _runQuery(const QString &query, const CancellationToken &token);
 
 private:
     void addDocsetsFromFolder(const QString &path);

src/ui/mainwindow.cpp

@@ -392,7 +392,9 @@ MainWindow::MainWindow(Core::Application *app, QWidget *parent) :
             return;
 
         currentTabState()->searchQuery = text;
-        m_application->docsetRegistry()->search(text);
+        m_cancelSearch.cancel();
+        m_cancelSearch = CancellationToken();
+        m_application->docsetRegistry()->search(text, m_cancelSearch);
         if (text.isEmpty()) {
             currentTabState()->tocModel->setResults();
             syncTreeView();

src/ui/mainwindow.h

@@ -25,6 +25,7 @@
 #define MAINWINDOW_H
 
 #include "registry/searchquery.h"
+#include "registry/cancellationtoken.h"
 
 #include <QMainWindow>
 
@@ -123,6 +124,8 @@ private slots:
     QMenu *m_backMenu = nullptr;
     QMenu *m_forwardMenu = nullptr;
 
+    Zeal::CancellationToken m_cancelSearch;
+
     QxtGlobalShortcut *m_globalShortcut = nullptr;
 
     QTabBar *m_tabBar = nullptr;