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265 lines
11 KiB
C++
265 lines
11 KiB
C++
/****************************************************************************
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**
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** Copyright (C) Qxt Foundation. Some rights reserved.
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**
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** This file is part of the QxtCore module of the Qxt library.
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**
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** This library is free software; you can redistribute it and/or modify it
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** under the terms of the Common Public License, version 1.0, as published
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** by IBM, and/or under the terms of the GNU Lesser General Public License,
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** version 2.1, as published by the Free Software Foundation.
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**
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** This file is provided "AS IS", without WARRANTIES OR CONDITIONS OF ANY
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** KIND, EITHER EXPRESS OR IMPLIED INCLUDING, WITHOUT LIMITATION, ANY
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** WARRANTIES OR CONDITIONS OF TITLE, NON-INFRINGEMENT, MERCHANTABILITY OR
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** FITNESS FOR A PARTICULAR PURPOSE.
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**
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** You should have received a copy of the CPL and the LGPL along with this
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** file. See the LICENSE file and the cpl1.0.txt/lgpl-2.1.txt files
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** included with the source distribution for more information.
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** If you did not receive a copy of the licenses, contact the Qxt Foundation.
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**
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** <http://libqxt.org> <foundation@libqxt.org>
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**
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****************************************************************************/
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#ifndef QXTBOUNDFUNCTION_H
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#define QXTBOUNDFUNCTION_H
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#include <QObject>
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#include <QMetaObject>
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#include <QGenericArgument>
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#include <qxtmetaobject.h>
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#include <qxtnull.h>
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#include <QThread>
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#include <QtDebug>
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/*!
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\class QxtBoundFunction
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\inmodule QxtCore
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\brief Binds parameters to a function call
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* A bound function is very similar to what the C++ FAQ Lite refers to as "functionoids."
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* (http://www.parashift.com/c++-faq-lite/pointers-to-members.html#faq-33.10)
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* It is similar in use to a function pointer, but allows any or all parameters to be
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* pre-filled with constant values. The remaining parameters are specified when the
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* function is invoked, for instance, by a Qt signal connection.
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*
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* By far, the most common expected use is to provide a parameter to a slot when the
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* signal doesn't have offer one. Many developers new to Qt try to write code like this:
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* \code
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* connect(button, SIGNAL(clicked()), lineEdit, SLOT(setText("Hello, world")));
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* \endcode
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* Experienced Qt developers will immediately spot the flaw here. The typical solution
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* is to create a short, one-line wrapper slot that invokes the desired function. Some
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* clever developers may even use QSignalMapper to handle slots that only need one
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* int or QString parameter.
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*
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* QxtBoundFunction enables the previous connect statement to be written like this:
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* \code
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* connect(button, SIGNAL(clicked()), QxtMetaObject::bind(lineEdit, SLOT(setText(QString)), Q_ARG(QString, "Hello, world!")));
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* \code
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* This accomplishes the same result without having to create a new slot, or worse,
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* an entire object, just to pass a constant value.
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*
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* Additionally, through the use of the QXT_BIND macro, parameters from the signal
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* can be rearranged, skipped, or passed alongside constant arguments provided
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* with the Q_ARG macro. This can be used to provide stateful callbacks to a
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* generic function, for example.
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*
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* Many kinds of functions can be bound. The most common binding applies to
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* Qt signals and slots, but standard C/C++ functions can be bound as well.
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* Future development may add the ability to bind to C++ member functions,
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* and developers can make custom QxtBoundFunction subclasses for even more
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* flexibility if necessary.
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*
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*
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*/
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class QXT_CORE_EXPORT QxtBoundFunction : public QObject
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{
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Q_OBJECT
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public:
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/*!
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* Invokes the bound function and returns a value.
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*
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* The template parameter should be the return type of the invoked function. This overload accepts
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* QVariant parameters and will guess the data type of each parameter based on the type of the QVariant.
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*/
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template <class T>
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inline QxtNullable<T> invoke(QXT_PROTO_10ARGS(QVariant))
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{
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if (!parent() || QThread::currentThread() == parent()->thread())
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return invoke<T>(Qt::DirectConnection, p1, p2, p3, p4, p5, p6, p7, p8, p9, p10);
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#if QT_VERSION >= 0x040300
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return invoke<T>(Qt::BlockingQueuedConnection, p1, p2, p3, p4, p5, p6, p7, p8, p9, p10);
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#else
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qWarning() << "QxtBoundFunction::invoke: Cannot return a value using a queued connection";
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return QxtNull();
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#endif
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}
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/*!
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* Invokes the bound function and returns a value.
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*
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* The template parameter should be the return type of the invoked function. This overload accepts
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* QGenericArgument parameters, expressed using the Q_ARG() macro.
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*/
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template <class T>
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QxtNullable<T> invoke(Qt::ConnectionType type, QVariant p1, QXT_PROTO_9ARGS(QVariant))
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{
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if (type == Qt::QueuedConnection)
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{
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qWarning() << "QxtBoundFunction::invoke: Cannot return a value using a queued connection";
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return QxtNull();
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}
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T retval;
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// I know this is a totally ugly function call
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if (invoke(type, QGenericReturnArgument(qVariantFromValue<T>(*reinterpret_cast<T*>(0)).typeName(), reinterpret_cast<void*>(&retval)),
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p1, p2, p3, p4, p5, p6, p7, p8, p9, p10))
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{
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return retval;
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}
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else
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{
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return QxtNull();
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}
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}
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/*!
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* Invokes the bound function, discarding the return value.
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*
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* This overload accepts QVariant parameters and will guess the data type of each
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* parameter based on the type of the QVariant.
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*
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* This function returns true if the invocation was successful, otherwise it
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* returns false.
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*/
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inline bool invoke(QVariant p1, QXT_PROTO_9ARGS(QVariant))
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{
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return invoke(Qt::AutoConnection, p1, p2, p3, p4, p5, p6, p7, p8, p9, p10);
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}
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/*!
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* Invokes the bound function, discarding the return value.
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*
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* This overload accepts QVariant parameters and will guess the data type of each
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* parameter based on the type of the QVariant. It also allows you to specify the
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* connection type, allowing the bound function to be invoked across threads using
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* the Qt event loop.
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*
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* This function returns true if the invocation was successful, otherwise it
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* returns false.
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*/
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bool invoke(Qt::ConnectionType, QVariant p1, QXT_PROTO_9ARGS(QVariant));
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/*!
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* Invokes the bound function, discarding the return value.
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*
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* This overload accepts QGenericArgument parameters, expressed using the Q_ARG()
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* macro.
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*
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* This function returns true if the invocation was successful, otherwise it
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* returns false.
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*/
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inline bool invoke(QXT_PROTO_10ARGS(QGenericArgument))
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{
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return invoke(Qt::AutoConnection, p1, p2, p3, p4, p5, p6, p7, p8, p9, p10);
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}
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/*!
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* Invokes the bound function, discarding the return value.
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*
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* This overload accepts QGenericArgument parameters, expressed using the Q_ARG()
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* macro. It also allows you to specify the connection type, allowing the bound
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* function to be invoked across threads using the Qt event loop.
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*
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* This function returns true if the invocation was successful, otherwise it
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* returns false.
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*/
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inline bool invoke(Qt::ConnectionType type, QXT_PROTO_10ARGS(QGenericArgument))
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{
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return invoke(type, QGenericReturnArgument(), p1, p2, p3, p4, p5, p6, p7, p8, p9, p10);
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}
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/*!
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* Invokes the bound function and assigns the return value to a parameter passed by reference.
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*
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* Use the Q_RETURN_ARG() macro to pass a reference to an assignable object of the function's
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* return type. When the function completes, its return value will be stored in that object.
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*
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* This overload accepts QVariant parameters and will guess the data type of each
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* parameter based on the type of the QVariant.
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*
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* This function returns true if the invocation was successful, otherwise it
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* returns false.
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*/
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inline bool invoke(QGenericReturnArgument returnValue, QVariant p1, QXT_PROTO_9ARGS(QVariant))
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{
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return invoke(Qt::AutoConnection, returnValue, p1, p2, p3, p4, p5, p6, p7, p8, p9, p10);
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}
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/*!
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* Invokes the bound function and assigns the return value to a parameter passed by reference.
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*
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* Use the Q_RETURN_ARG() macro to pass a reference to an assignable object of the function's
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* return type. When the function completes, its return value will be stored in that object.
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*
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* This overload accepts QVariant parameters and will guess the data type of each
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* parameter based on the type of the QVariant. It also allows you to specify the
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* connection type, allowing the bound function to be invoked across threads using
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* the Qt event loop.
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*
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* This function returns true if the invocation was successful, otherwise it
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* returns false.
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*/
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bool invoke(Qt::ConnectionType type, QGenericReturnArgument returnValue, QVariant p1, QXT_PROTO_9ARGS(QVariant));
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/*!
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* Invokes the bound function and assigns the return value to a parameter passed by reference.
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*
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* Use the Q_RETURN_ARG() macro to pass a reference to an assignable object of the function's
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* return type. When the function completes, its return value will be stored in that object.
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*
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* This overload accepts QGenericArgument parameters, expressed using the Q_ARG()
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* macro.
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*
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* This function returns true if the invocation was successful, otherwise it
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* returns false.
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*/
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inline bool invoke(QGenericReturnArgument returnValue, QXT_PROTO_10ARGS(QGenericArgument))
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{
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return invoke(Qt::AutoConnection, returnValue, p1, p2, p3, p4, p5, p6, p7, p8, p9, p10);
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}
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/*!
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* Invokes the bound function and assigns the return value to a parameter passed by reference.
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*
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* Use the Q_RETURN_ARG() macro to pass a reference to an assignable object of the function's
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* return type. When the function completes, its return value will be stored in that object.
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*
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* This overload accepts QGenericArgument parameters, expressed using the Q_ARG()
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* macro. It also allows you to specify the connection type, allowing the bound
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* function to be invoked across threads using the Qt event loop.
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*
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* This function returns true if the invocation was successful, otherwise it
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* returns false.
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*/
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bool invoke(Qt::ConnectionType type, QGenericReturnArgument returnValue, QXT_PROTO_10ARGS(QGenericArgument));
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protected:
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#ifndef QXT_DOXYGEN_RUN
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QxtBoundFunction(QObject* parent = 0);
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#endif
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/*!
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* Performs the work of invoking the bound function.
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*
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* This function is pure virtual. The various QxtMetaObject::bind() functions return opaque subclasses
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* of QxtBoundFunction. If you wish to create a new kind of bound function, reimplement this function to
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* perform the invocation and assign the function's return value, if any, to the returnValue parameter.
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*
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* This function should return true if the invocation is successful and false if an error occurs.
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*/
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virtual bool invokeImpl(Qt::ConnectionType type, QGenericReturnArgument returnValue, QXT_PROTO_10ARGS(QGenericArgument)) = 0;
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};
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#endif
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