forked from qt-creator/qt-creator
123 lines
6.0 KiB
Plaintext
123 lines
6.0 KiB
Plaintext
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/****************************************************************************
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**
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** This file is part of Qt Creator
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**
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** Copyright (c) 2011 Nokia Corporation and/or its subsidiary(-ies).
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**
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** Contact: Nokia Corporation (info@qt.nokia.com)
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**
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**
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** GNU Free Documentation License
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**
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** Alternatively, this file may be used under the terms of the GNU Free
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** Documentation License version 1.3 as published by the Free Software
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** Foundation and appearing in the file included in the packaging of this
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** file.
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**
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** If you have questions regarding the use of this file, please contact
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** Nokia at info@qt.nokia.com.
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**
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****************************************************************************/
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/*!
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\page plugin-lifecycle.html
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\title Plugin Life Cycle
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To be able to write \QC plugins, you must understand the steps that the plugin
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manager takes when you start or shut down \QC. This section describes
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the process and the state that plugins go through in detail.
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When you start \QC, the plugin manager does the following:
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\list 1
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\o Looks in its search paths for
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all .pluginspec files, and reads them. This is the first point where
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loading a plugin can fail in the worst case of a malformed plugin spec.
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\o Creates an instance of the \l{ExtensionSystem::PluginSpec} class for
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each plugin. This class is a container for
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all the information from the plugin specification, and additionally
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tracks the state of the plugin.
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You can get the \l{ExtensionSystem::PluginSpec} instances via the
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plugin manager's \l{ExtensionSystem::PluginManager::plugins()}{plugins()}
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method, or, after a plugin is loaded, through the plugin's
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\l{ExtensionSystem::IPlugin::pluginSpec()}{pluginSpec()} method.
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\o Sets the plugins to \c Read state.
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\o Verifies that the dependencies of each plugin
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exist and are compatible. For more information about plugin dependencies,
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see \l{Plugin Specifications}.
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\o Sets the plugins to \c Resolved state.
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\o Sorts all plugins into a list that we call the \e{load queue}, where the
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dependencies of a plugin are positioned after the plugin
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(but not necessarily \e directly after the plugin).
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It will make sure that we load
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and initialize the plugins in proper order.
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\o Loads the plugins' libraries, and creates their IPlugin instances
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in the order of the load queue. At this point the
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plugin constructors are called. Plugins that other plugins depend on
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are created first.
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\o Sets the plugins to \c Loaded state.
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\o Calls the \l{ExtensionSystem::IPlugin::initialize()}{initialize()} methods of
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all plugins in the order of the load queue. In the initialize method,
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a plugin should make sure that all exported interfaces are set up and available
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to other plugins. A plugin can assume that plugins they depend on have set up
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their exported interfaces. For example, the \c Core plugin sets up the
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\l{Core::ActionManager}, \l{Core::EditorManager} and all other publicly available
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interfaces, so other plugins can request and use them.
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The \l{ExtensionSystem::IPlugin::initialize()}{initialize()} method of a plugin
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is a good place for
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\list
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\o registering objects in the plugin manager's object pool
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(see \l{The Plugin Manager, the Object Pool, and Registered Objects})
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\o loading settings
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\o adding new menus, and new actions to menus
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\o connecting to other plugin's signals.
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\endlist
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\o Sets the plugins to \c Initialized state.
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\o Calls the \l{ExtensionSystem::IPlugin::extensionsInitialized()}{extensionsInitialized()}
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methods of all plugins in \e reverse order of the load queue. After
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the extensionsInitialized method, a plugin should be fully initialized, set up
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and running. A plugin can assume that plugins that depend on it are fully set up,
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and can finish the initialization of parts that can be extended by other plugins.
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For example, the \c Core plugin assumes that all plugins have registered
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their actions, and finishes initialization of the action manager.
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\o Sets the plugins to \c Running state.
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\endlist
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At the end of startup, the \c Core plugin's \l{Core::ICore} sends two signals.
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Before the \QC UI is shown it sends \l{Core::ICore::coreAboutToOpen()}{coreAboutToOpen()},
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and afterwards \l{Core::ICore::coreOpened()}{coreOpened()}.
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Before shutdown, the \c Core plugin's \l{Core::ICore} sends the
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\l{Core::ICore::coreAboutToClose()}{coreAboutToClose()} signal. After that, the
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plugin manager starts its shutdown sequence:
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\list 1
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\o Calls the \l{ExtensionSystem::IPlugin::aboutToShutdown()}{aboutToShutdown()} methods of
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all plugins in the order of the load queue. Plugins should perform measures
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for speeding up the actual shutdown here, like disconnecting signals that
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would otherwise needlessly be called.
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If a plugin needs to delay the real shutdown for a while, for example if
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it needs to wait for external processes to finish for a clean shutdown,
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the plugin can return \l{ExtensionSystem::IPlugin::AsynchronousShutdown} from this
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method. This will make the plugin manager wait with the next step, and keep the main
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event loop running, until all plugins requesting AsynchronousShutdown have sent
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the asynchronousShutdownFinished() signal.
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\o Destroys all plugins by deleting their \l{ExtensionSystem::IPlugin}
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instances in \e reverse order of the load queue. At this point the plugin destructors
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are called. Plugins should clean up after themselves by freeing memory and other resources.
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\endlist
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*/
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