/**************************************************************************** ** ** Copyright (C) 2012 Nokia Corporation and/or its subsidiary(-ies). ** All rights reserved. ** Contact: Nokia Corporation (qt-info@nokia.com) ** ** This file is part of the documentation of the Qt Toolkit. ** ** $QT_BEGIN_LICENSE:FDL$ ** GNU Free Documentation License ** Alternatively, this file may be used under the terms of the GNU Free ** Documentation License version 1.3 as published by the Free Software ** Foundation and appearing in the file included in the packaging of ** this file. ** ** Other Usage ** Alternatively, this file may be used in accordance with the terms ** and conditions contained in a signed written agreement between you ** and Nokia. ** ** ** ** ** $QT_END_LICENSE$ ** ****************************************************************************/ /*! \example designer/worldtimeclockplugin \title World Time Clock Plugin Example \brief The World Time Clock Plugin example shows how to create a custom widget plugin for \QD that uses signals and slots. \image worldtimeclockplugin-example.png In this example, we simply extend the \l {designer/customwidgetplugin}{Custom Widget Plugin} example and its custom widget (based on the \l{widgets/analogclock}{Analog Clock} example), by introducing the concept of signals and slots. The World Time Clock Plugin example consists of two classes: \list \o \c WorldTimeClock is a custom clock widget with hour and minute hands that is automatically updated every few seconds. \o \c WorldTimeClockPlugin exposes the \c WorldTimeClock class to \QD. \endlist First we will take a look at the \c WorldTimeClock class which extends the \l {designer/customwidgetplugin}{Custom Widget Plugin} example's \c AnalogClock class by providing a signal and a slot. Then we will take a quick look at the \c WorldTimeClockPlugin class, but this class is in most parts identical to the \l {designer/customwidgetplugin}{Custom Widget Plugin} example's implementation. Finally we take a look at the plugin's project file. The project file for custom widget plugins needs some additional information to ensure that they will work within \QD. This is also covered in the \l {designer/customwidgetplugin}{Custom Widget Plugin} example, but due to its importance (custom widget plugins rely on components supplied with \QD which must be specified in the project file that we use) we will repeat it here. \section1 WorldTimeClock Class The \c WorldTimeClock class inherits QWidget, and is a custom clock widget with hour and minute hands that is automatically updated every few seconds. What makes this example different from the \l {designer/customwidgetplugin}{Custom Widget Plugin} example, is the introduction of the signal and slot in the custom widget class: \snippet examples/designer/worldtimeclockplugin/worldtimeclock.h 1 Note the use of the QDESIGNER_WIDGET_EXPORT macro. This is needed to ensure that \QD can create instances of the widget on some platforms, but it is a good idea to use it on all platforms. We declare the \c setTimeZone() slot with an associated \c timeZoneOffset variable, and we declare an \c updated() signal which takes the current time as argument and is emitted whenever the widget is repainted. \image worldtimeclock-connection.png In \QD's workspace we can then, for example, connect the \c WorldTimeClock widget's \c updated() signal to a QTimeEdit's \l {QDateTimeEdit::setTime()}{setTime()} slot using \QD's mode for editing signal and slots. \image worldtimeclock-signalandslot.png We can also connect a QSpinBox's \l {QSpinBox::valueChanged()}{valueChanged()} signal to the \c WorldTimeClock's \c setTimeZone() slot. \section1 WorldTimeClockPlugin Class The \c WorldTimeClockPlugin class exposes the \c WorldTimeClock class to \QD. Its definition is equivalent to the \l {designer/customwidgetplugin}{Custom Widget Plugin} example's plugin class which is explained in detail. The only part of the class definition that is specific to this particular custom widget is the class name: \snippet examples/designer/worldtimeclockplugin/worldtimeclockplugin.h 0 The plugin class provides \QD with basic information about our plugin, such as its class name and its include file. Furthermore it knows how to create instances of the \c WorldTimeClockPlugin widget. \c WorldTimeClockPlugin also defines the \l {QDesignerCustomWidgetInterface::initialize()}{initialize()} function which is called after the plugin is loaded into \QD. The function's QDesignerFormEditorInterface parameter provides the plugin with a gateway to all of \QD's API's. The \c WorldTimeClockPlugin class inherits from both QObject and QDesignerCustomWidgetInterface. It is important to remember, when using multiple inheritance, to ensure that all the interfaces (i.e. the classes that doesn't inherit Q_OBJECT) are made known to the meta object system using the Q_INTERFACES() macro. This enables \QD to use \l qobject_cast() to query for supported interfaces using nothing but a QObject pointer. The implementation of the \c WorldTimeClockPlugin is also equivalent to the plugin interface implementation in the \l {designer/customwidgetplugin}{Custom Widget Plugin} example (only the class name and the implementation of QDesignerCustomWidgetInterface::domXml() differ). The main thing to remember is to use the Q_EXPORT_PLUGIN2() macro to export the \c WorldTimeClockPlugin class for use with \QD: \snippet examples/designer/worldtimeclockplugin/worldtimeclockplugin.cpp 0 Without this macro, there is no way for Qt Designer to use the widget. \section1 The Project File: worldtimeclockplugin.pro The project file for custom widget plugins needs some additional information to ensure that they will work as expected within \QD: \snippet examples/designer/worldtimeclockplugin/worldtimeclockplugin.pro 0 \snippet examples/designer/worldtimeclockplugin/worldtimeclockplugin.pro 1 The \c TEMPLATE variable's value make \c qmake create the custom widget as a library. The \c CONFIG variable contains two values, \c designer and \c plugin: \list \o \c designer: Since custom widgets plugins rely on components supplied with \QD, this value ensures that our plugin links against \QD's library (\c libQtDesigner.so). \o \c plugin: We also need to ensure that \c qmake considers the custom widget a \e plugin library. \endlist When Qt is configured to build in both debug and release modes, \QD will be built in release mode. When this occurs, it is necessary to ensure that plugins are also built in release mode. For that reason you might have to add a \c release value to your \c CONFIG variable. Otherwise, if a plugin is built in a mode that is incompatible with \QD, it won't be loaded and installed. The header and source files for the widget are declared in the usual way, and in addition we provide an implementation of the plugin interface so that \QD can use the custom widget. \snippet examples/designer/worldtimeclockplugin/worldtimeclockplugin.pro 2 It is important to ensure that the plugin is installed in a location that is searched by \QD. We do this by specifying a target path for the project and adding it to the list of items to install: \snippet doc/src/snippets/code/doc_src_examples_worldtimeclockplugin.pro 0 The custom widget is created as a library, and will be installed alongside the other \QD plugins when the project is installed (using \c{make install} or an equivalent installation procedure). Later, we will ensure that it is recognized as a plugin by \QD by using the Q_EXPORT_PLUGIN2() macro to export the relevant widget information. Note that if you want the plugins to appear in a Visual Studio integration, the plugins must be built in release mode and their libraries must be copied into the plugin directory in the install path of the integration (for an example, see \c {C:/program files/trolltech as/visual studio integration/plugins}). For more information about plugins, see the \l {How to Create Qt Plugins} document. */