summaryrefslogtreecommitdiff
path: root/src/webchannel/signalhandler_p.h
blob: 8f8c34917a98ff9f2794f0d41107787f4d7345f1 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
/****************************************************************************
**
** Copyright (C) 2016 Klarälvdalens Datakonsult AB, a KDAB Group company, info@kdab.com, author Milian Wolff <milian.wolff@kdab.com>
** Contact: https://www.qt.io/licensing/
**
** This file is part of the QtWebChannel module of the Qt Toolkit.
**
** $QT_BEGIN_LICENSE:LGPL$
** Commercial License Usage
** Licensees holding valid commercial Qt licenses may use this file in
** accordance with the commercial license agreement provided with the
** Software or, alternatively, in accordance with the terms contained in
** a written agreement between you and The Qt Company. For licensing terms
** and conditions see https://www.qt.io/terms-conditions. For further
** information use the contact form at https://www.qt.io/contact-us.
**
** GNU Lesser General Public License Usage
** Alternatively, this file may be used under the terms of the GNU Lesser
** General Public License version 3 as published by the Free Software
** Foundation and appearing in the file LICENSE.LGPL3 included in the
** packaging of this file. Please review the following information to
** ensure the GNU Lesser General Public License version 3 requirements
** will be met: https://www.gnu.org/licenses/lgpl-3.0.html.
**
** GNU General Public License Usage
** Alternatively, this file may be used under the terms of the GNU
** General Public License version 2.0 or (at your option) the GNU General
** Public license version 3 or any later version approved by the KDE Free
** Qt Foundation. The licenses are as published by the Free Software
** Foundation and appearing in the file LICENSE.GPL2 and LICENSE.GPL3
** included in the packaging of this file. Please review the following
** information to ensure the GNU General Public License requirements will
** be met: https://www.gnu.org/licenses/gpl-2.0.html and
** https://www.gnu.org/licenses/gpl-3.0.html.
**
** $QT_END_LICENSE$
**
****************************************************************************/

#ifndef SIGNALHANDLER_H
#define SIGNALHANDLER_H

//
//  W A R N I N G
//  -------------
//
// This file is not part of the Qt API.  It exists purely as an
// implementation detail.  This header file may change from version to
// version without notice, or even be removed.
//
// We mean it.
//

#include <QObject>
#include <QHash>
#include <QList>
#include <QMetaMethod>
#include <QDebug>

QT_BEGIN_NAMESPACE

static const int s_destroyedSignalIndex = QObject::staticMetaObject.indexOfMethod("destroyed(QObject*)");

/**
 * The signal handler is similar to QSignalSpy, but geared towards the usecase of the web channel.
 *
 * It allows connecting to any number of signals of arbitrary objects and forwards the signal
 * invocations to the Receiver by calling its signalEmitted function, which takes the object,
 * signal index and a QVariantList of arguments.
 */
template<class Receiver>
class SignalHandler : public QObject
{
public:
    SignalHandler(Receiver *receiver, QObject *parent = 0);

    /**
     * Connect to a signal of @p object identified by @p signalIndex.
     *
     * If the handler is already connected to the signal, an internal counter is increased,
     * i.e. the handler never connects multiple times to the same signal.
     */
    void connectTo(const QObject *object, const int signalIndex);

    /**
     * Decrease the connection counter for the connection to the given signal.
     *
     * When the counter drops to zero, the connection is disconnected.
     */
    void disconnectFrom(const QObject *object, const int signalIndex);

    /**
     * @internal
     *
     * Custom implementation of qt_metacall which calls dispatch() for connected signals.
     */
    int qt_metacall(QMetaObject::Call call, int methodId, void **args) override;

    /**
     * Reset all connections, useful for benchmarks.
     */
    void clear();

    /**
     * Fully remove and disconnect an object from handler
     */
    void remove(const QObject *object);

private:
    /**
     * Exctract the arguments of a signal call and pass them to the receiver.
     *
     * The @p argumentData is converted to a QVariantList and then passed to the receiver's
     * signalEmitted method.
     */
    void dispatch(const QObject *object, const int signalIdx, void **argumentData);

    void setupSignalArgumentTypes(const QMetaObject *metaObject, const QMetaMethod &signal);

    Receiver *m_receiver;

    // maps meta object -> signalIndex -> list of arguments
    // NOTE: This data is "leaked" on disconnect until deletion of the handler, is this a problem?
    typedef QList<int> ArgumentTypeList;
    typedef QHash<int, ArgumentTypeList> SignalArgumentHash;
    QHash<const QMetaObject *, SignalArgumentHash > m_signalArgumentTypes;

    /*
     * Tracks how many connections are active to object signals.
     *
     * Maps object -> signalIndex -> pair of connection and number of connections
     *
     * Note that the handler is connected to the signal only once, whereas clients
     * may have connected multiple times.
     *
     * TODO: Move more of this logic to the HTML client side, esp. the connection counting.
     */
    typedef QPair<QMetaObject::Connection, int> ConnectionPair;
    typedef QHash<int, ConnectionPair> SignalConnectionHash;
    typedef QHash<const QObject*, SignalConnectionHash> ConnectionHash;
    ConnectionHash m_connectionsCounter;
};

template<class Receiver>
SignalHandler<Receiver>::SignalHandler(Receiver *receiver, QObject *parent)
    : QObject(parent)
    , m_receiver(receiver)
{
    // we must know the arguments of a destroyed signal for the global static meta object of QObject
    // otherwise, we might end up with missing m_signalArgumentTypes information in dispatch
    setupSignalArgumentTypes(&QObject::staticMetaObject, QObject::staticMetaObject.method(s_destroyedSignalIndex));
}

/**
 * Find and return the signal of index @p signalIndex in the meta object of @p object and return it.
 *
 * The return value is also verified to ensure it is a signal.
 */
inline QMetaMethod findSignal(const QMetaObject *metaObject, const int signalIndex)
{
    QMetaMethod signal = metaObject->method(signalIndex);
    if (!signal.isValid()) {
        qWarning("Cannot find signal with index %d of object %s", signalIndex, metaObject->className());
        return QMetaMethod();
    }
    Q_ASSERT(signal.methodType() == QMetaMethod::Signal);
    return signal;
}

template<class Receiver>
void SignalHandler<Receiver>::connectTo(const QObject *object, const int signalIndex)
{
    const QMetaObject *metaObject = object->metaObject();
    const QMetaMethod &signal = findSignal(metaObject, signalIndex);
    if (!signal.isValid()) {
        return;
    }

    ConnectionPair &connectionCounter = m_connectionsCounter[object][signalIndex];
    if (connectionCounter.first) {
        // increase connection counter if already connected
        ++connectionCounter.second;
        return;
    } // otherwise not yet connected, do so now

    static const int memberOffset = QObject::staticMetaObject.methodCount();
    QMetaObject::Connection connection = QMetaObject::connect(object, signal.methodIndex(), this, memberOffset + signalIndex, Qt::AutoConnection, 0);
    if (!connection) {
        qWarning() << "SignalHandler: QMetaObject::connect returned false. Unable to connect to" << object << signal.name() << signal.methodSignature();
        return;
    }
    connectionCounter.first = connection;
    connectionCounter.second = 1;

    setupSignalArgumentTypes(metaObject, signal);
}

template<class Receiver>
void SignalHandler<Receiver>::setupSignalArgumentTypes(const QMetaObject *metaObject, const QMetaMethod &signal)
{
    if (m_signalArgumentTypes.value(metaObject).contains(signal.methodIndex())) {
        return;
    }
    // find the type ids of the signal parameters, see also QSignalSpy::initArgs
    QList<int> args;
    args.reserve(signal.parameterCount());
    for (int i = 0; i < signal.parameterCount(); ++i) {
        int tp = signal.parameterType(i);
        if (tp == QMetaType::UnknownType) {
            qWarning("Don't know how to handle '%s', use qRegisterMetaType to register it.",
                    signal.parameterNames().at(i).constData());
        }
        args << tp;
    }

    m_signalArgumentTypes[metaObject][signal.methodIndex()] = args;
}

template<class Receiver>
void SignalHandler<Receiver>::dispatch(const QObject *object, const int signalIdx, void **argumentData)
{
    Q_ASSERT(m_signalArgumentTypes.contains(object->metaObject()));
    const QHash<int, QList<int>> &objectSignalArgumentTypes = m_signalArgumentTypes.value(object->metaObject());
    QHash<int, QList<int>>::const_iterator signalIt = objectSignalArgumentTypes.constFind(signalIdx);
    if (signalIt == objectSignalArgumentTypes.constEnd()) {
        // not connected to this signal, skip
        return;
    }
    const QList<int> &argumentTypes = *signalIt;
    QVariantList arguments;
    arguments.reserve(argumentTypes.count());
    // TODO: basic overload resolution based on number of arguments?
    for (int i = 0; i < argumentTypes.count(); ++i) {
        const QMetaType::Type type = static_cast<QMetaType::Type>(argumentTypes.at(i));
        QVariant arg;
        if (type == QMetaType::QVariant) {
            arg = *reinterpret_cast<QVariant *>(argumentData[i + 1]);
        } else {
            arg = QVariant(type, argumentData[i + 1]);
        }
        arguments.append(arg);
    }
    m_receiver->signalEmitted(object, signalIdx, arguments);
}

template<class Receiver>
void SignalHandler<Receiver>::disconnectFrom(const QObject *object, const int signalIndex)
{
    Q_ASSERT(m_connectionsCounter.value(object).contains(signalIndex));
    ConnectionPair &connection = m_connectionsCounter[object][signalIndex];
    --connection.second;
    if (!connection.second || !connection.first) {
        QObject::disconnect(connection.first);
        m_connectionsCounter[object].remove(signalIndex);
        if (m_connectionsCounter[object].isEmpty()) {
            m_connectionsCounter.remove(object);
        }
    }
}

template<class Receiver>
int SignalHandler<Receiver>::qt_metacall(QMetaObject::Call call, int methodId, void **args)
{
    methodId = QObject::qt_metacall(call, methodId, args);
    if (methodId < 0)
        return methodId;

    if (call == QMetaObject::InvokeMetaMethod) {
        const QObject *object = sender();
        Q_ASSERT(object);
        Q_ASSERT(senderSignalIndex() == methodId);
        Q_ASSERT(m_connectionsCounter.contains(object));
        Q_ASSERT(m_connectionsCounter.value(object).contains(methodId));

        dispatch(object, methodId, args);

        return -1;
    }
    return methodId;
}

template<class Receiver>
void SignalHandler<Receiver>::clear()
{
    foreach (const SignalConnectionHash &connections, m_connectionsCounter) {
        foreach (const ConnectionPair &connection, connections) {
            QObject::disconnect(connection.first);
        }
    }
    m_connectionsCounter.clear();
    const SignalArgumentHash keep = m_signalArgumentTypes.take(&QObject::staticMetaObject);
    m_signalArgumentTypes.clear();
    m_signalArgumentTypes[&QObject::staticMetaObject] = keep;
}

template<class Receiver>
void SignalHandler<Receiver>::remove(const QObject *object)
{
    Q_ASSERT(m_connectionsCounter.contains(object));
    const SignalConnectionHash &connections = m_connectionsCounter.value(object);
    foreach (const ConnectionPair &connection, connections) {
        QObject::disconnect(connection.first);
    }
    m_connectionsCounter.remove(object);
}

QT_END_NAMESPACE

#endif // SIGNALHANDLER_H