/************************************************************************** ** ** Copyright (c) 2012 Digia Plc and/or its subsidiary(-ies). ** Contact: http://www.qt-project.org/legal ** ** This file is part of Qt Creator ** ** ** 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. ** ** **************************************************************************/ /*! \page first-plugin.html \title Creating Your First Plugin This section describes how to create a \QC plugin by using the plugin template provided by \QC, and get the first impression of what a plugin consists of and what its general structure is. \section1 Creating a Plugin Project \QC comes with a wizard for \QC plugins, that creates a runable, \e minimal plugin for you. We strongly suggest that you use two different \QC instances for developing and testing your plugin with. Otherwise your plugin will also be loaded in your development environment, which can make that unstable while your plugin is still unstable. You can just create a copy of your \QC build and use one for actually developing, and the other for testing your plugin with. \list 1 \o Select \gui{File > New File or Project > Libraries > Qt Creator Plugin > Choose}. \image firstplugin-wizard.png "Choose the \QC Plugin Wizard" The \gui{Introduction and Project Location} dialog opens. \image firstplugin-nameandpath.png "Choose Name and Place of the Project" \o Give your project a name and specify in which path this project will be created. The actual plugin's name can be different from the project name. You will choose that name later in the wizard. Continue to the next page. The \gui{Kit Selection} dialog opens. \image firstplugin-kitselection.png "Choose the kit to build and run your project with" \o Select the \l{glossary-buildandrun-kit}{kit} to build and run your project with. For a \QC plugin this needs to be a kit with \gui{Desktop} device type, and a Qt version that is compatible with the Qt version that your \QC was built with (in the best case the exact same build). If you use an incompatible Qt version to build your plugin, you will get errors while \QC tries to load your plugin. Continue to the next page. The \gui{Plugin Information} dialog opens. \image firstplugin-pluginsetup.png "Specify Your Plugin Details" \o In the \gui{Plugin name} field, type \gui{Example}. The name of the plugin is used as its identifier, and also is the base for the file names and classes in the code. \o The values of the following fields are mainly informational, and are shown in the detailed view in \QC's plugin overview (\gui{Help > About Plugins}, or \gui{Qt Creator > About Plugins} on Mac). \list \o \gui{Vendor name} is a short one-word name of the company or organization that created the plugin. This is also used for the path name where the plugin will be deployed to. \o \gui{Copyright} is a one-line, short copyright string. \o \gui{License} is a multi-line license text (but shouldn't be pages over pages long, since the interface doesn't allow nice reading of long texts). \o \gui{Description} is a relatively short, but possibly multi-line description of what the plugin does. \o \gui{URL} is a website where the user can find more information about the plugin and/or organization providing it. \endlist \o Set the \gui{Qt Creator sources} and \gui{Qt Creator build} fields to the source and build directory of the \QC instance you want to use to test your plugin with, respectively. If you don't do that correctly you will get compile errors for your plugin, and your plugin might not show up in \QC at all. \o In the \gui{Deploy into} list, select \gui{Qt Creator build}. This sets your .pro file up to deploy your plugin directly into your \QC build's plugin directory (requires you to have write permissions there). The other option, \gui{Local user settings}, sets your .pro file up to deploy your plugin into \QC's user plugin path (for example \c{~/.config/QtProject/qtcreator/plugins} on Unix systems). We choose \gui{Qt Creator build} because we use a self-compiled \QC, and want the plugin to be only loaded by that \QC instance. Continue to the next page. The \gui{Project Management} dialog opens. \image firstplugin-summary.png "Summary of Created Files" \o Review the files that will be created, choose a version control system that \QC should use for your project (always a good idea!), and finish the wizard. \endlist \section1 Building and Running the Plugin If you passed the correct \QC source and build paths in the project wizard, your plugin should just build fine when pressing the build button. When you try to run your project, \QC will ask you for the executable to run and you are presented the following dialog: \image firstplugin-runsettings.png "Specify the Executable to Run" Select the path to the \QC executable from the build that you specified in the \gui{Qt Creator build} setting in the project wizard and click \gui OK. \QC starts up, and you can verify that your plugin successfully loaded by looking for a menu entry \gui{Tools > Example} and by looking for the plugin in the \gui{About Plugins} dialog. \image firstplugin-menuitem.png "Menu Registered by the Plugin" \section1 File Structure The plugin wizard creates a set of basic files that a plugin needs or should have. We will have a look at some of them in detail in the following sections, here is a short overview: \table \header \o File \o Role \row \o \c{Example.pluginspec.in} \o Template plugin specification. QMake creates a \c{Example.pluginspec} from this file, which is read by \QC to find out about the plugin. \row \o \c{example.pro} \o Project file, used by QMake to generate a Makefile that then is used to build the plugin. \row \o \c{example_global.h} \o Contains macro definitions that are useful when this plugin should export symbols to other plugins. \row \o \c{exampleconstants.h} \o Header defining constants used by the plugin code. \row \o \c{exampleplugin.h/.cpp} \o C++ header and source files that define the plugin class that will be instanciated and run by \QC's plugin manager. \endtable \section1 qmake Project The qmake project file \c{example.pro} defines how your plugin should be compiled. \QC plugins need to have a specific setup there, in addition to telling qmake which files need to be compiled (or handled by \c moc or \c uic). Let us have a look at what the project wizard generated for you in detail. \snippet exampleplugin/example.pro 1 The first section of the .pro file defines the very basic properties of your project, the name (\c{TARGET}), and that a library should be generated, since plugins are actually libraries that are dynamically loaded (\c{TEMPLATE = lib}). The section also lets the compiler pass an \c EXAMPLE_LIBRARY define to the compiled code, which is used in the \c{example_global.h} header, but is not really of interest for now. You should not need to change that section of the .pro file. \snippet exampleplugin/example.pro 2 This section tells qmake about the files of your project that it should let compile or otherwise handle. You need to expand that section with any files you add to the project. \snippet exampleplugin/example.pro 3 To compile and deploy your plugin, the project needs access to the \QC sources and build. This section contains the logic that looks for the information about the location of the sources and build in the \c{QTC_SOURCE} and \c{QTC_BUILD} environment variables. If these are not defined, it uses the defaults you set in the project wizard. So, if someone else opens your plugin project on their machine, they do not need to edit the .pro file, but instead they should set the \c{QTC_SOURCE} and \c{QTC_BUILD} environment variables correctly for the plugin's build environment. You should not need to change this section, except perhaps to adapt the defaults. \snippet exampleplugin/example.pro 4 \QC plugins can either be installed into the \QC installation's plugin directory (requires write access there), or to a user specific plugin directory. The \c USE_USER_DESTDIR switch in the .pro file defines which method is used for building the plugin (which is independent from what you can later use for distributing your plugin to other users). \snippet exampleplugin/example.pro 5 The \c{PROVIDER} variable is for example used to deploy your plugin to a provider specific plugin subdirectory, and the value is taken from the information that you gave in the plugin project wizard. \snippet exampleplugin/example.pro 6 This section includes the necessary parts from the \QC sources and makes your plugin find the \QC libraries and plugins. The included file \c{qtcreatorplugin.pri} makes sure that you build a plugin that is suitable for use in \QC. The file \c{plugins/coreplugin/coreplugin.pri} makes your plugin dependent on the Core plugin and makes sure that you can access its public API. If you want to use or extend functionality from other plugins, you need to add the corresponding .pri file of the plugin here. For more information about qmake, and writing .pro files in general, see the \l{http://qt-project.org/doc/qt-4.8/qmake-manual.html}{qmake Manual}. \section1 Plugin Specification The .pluginspec file is an XML file that contains information that is needed by the plugin manager to find your plugin and resolve its dependencies before actually loading your plugin's library file. We will only have a short look at it here. For more information, see \l{Plugin Specifications}. The wizard doesn't actually create a .pluginspec file directly, but instead a .pluginspec.in file. qmake uses this to generate the actual plugin specification file, replacing variables like \c{QTCREATOR_VERSION} with their actual values. Therefore you need to escape all backslashes and quotes in the .pluginspec.in file (i.e. you need to write \c{\\} to get a backslash and \c{\"} to get a quote in the generated plugin specification). \snippet exampleplugin/Example.pluginspec.in 1 The main tag of the plugin specification that is created by the wizard defines the name of your plugin, its version, and with what version of this plugin the current version is binary compatible with. \snippet exampleplugin/Example.pluginspec.in 2 After the main tag you'll find the information about the plugin that you gave in the project wizard. \snippet exampleplugin/Example.pluginspec.in 3 The last section tells the plugin manager about the dependencies of this plugin. Most \QC plugins will at least depend on the \c{Core} plugin. \section1 Plugin Class The files \c{exampleplugin.h} and \c{exampleplugin.cpp} define the plugin implementation of your little plugin. We'll concentrate on some highlights here, and give pointers to more detailed information for the various parts. \section2 Header File The header file \c{exampleplugin.h} defines the interface of the plugin class. \snippet exampleplugin/exampleplugin.h namespaces The plugin is defined in a \c{Example::Internal} namespace, which conforms to the coding rules for \l{coding-rules-namespacing}{namespacing} in \QC sources. \snippet exampleplugin/exampleplugin.h base class All \QC plugins must be derived from \l{ExtensionSystem::IPlugin} and are QObjects. \snippet exampleplugin/exampleplugin.h plugin methods The base class defines basic methods that are called during the life cycle of a plugin, which are here implemented for your new plugin. These methods and their roles are described in detail in \l{The Plugin Life Cycle}. \snippet exampleplugin/exampleplugin.h slot The plugin has an additional custom slot, that is used to pop up a dialog when the user chooses the menu item that this plugin adds. \section2 Source File The source file contains the actual implementation of the plugin, which registers a new menu and menu item, and opens a message box when that item is triggered. All the necessary header files from the plugin code itself, from the Core plugin, and from Qt are included in the beginning of the file. The setup of the menu and menu item is done in the plugin's \c{initialize} method, which is the first thing called after the plugin constructor. In that method, the plugin can be sure that the basic setup of plugin's that it depends on has been done, for example the Core plugin's \c{ActionManager} instance has been created. For more information about implementing the plugin interface, see the \l{ExtensionSystem::IPlugin} API documentation and \l{Plugin Life Cycle}. \snippet exampleplugin/exampleplugin.cpp add action This part of the code creates a new \c{QAction}, registers it as a new \c{Command} in the action manager, and connects it to the plugin's slot. The action manager provides a central place where the user can assign and change keyboard shortcuts, and manages cases where for example a menu item should be directed to different plugins under different circumstances, as well as a few other things. This is described in more detail in \l{Menus and Menu Items}. \snippet exampleplugin/exampleplugin.cpp add menu Here a new menu item is created, the created command added to it, and the menu added to the \gui{Tools} menu in the menu bar. Again, this is covered in more detail in \l{Menus and Menu Items}. \snippet exampleplugin/exampleplugin.cpp slot implementation This part defines the code that is called when the menu item is triggered. It uses the Qt API to open a message box that displays informative text and an \gui OK button. \snippet exampleplugin/exampleplugin.cpp export plugin At the end of the file, the Qt macro \c{Q_EXPORT_PLUGIN2} is used to register the plugin with Qt's plugin loader system. This is necessary for Qt to be able to load your plugin. */