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++ // Copyright (C) 2016 The Qt Company Ltd.
++ // SPDX-License-Identifier: LicenseRef-Qt-Commercial OR GFDL-1.3-no-invariants-only
++
++ /*!
++ \page deployment-plugins.html
++ \title Deploying Plugins
++ \brief A guide to the plugin-specific aspects of deploying Qt and Qt Applications.
++
++ This topic explains how to deploy plugin libraries for Qt or your application to load at
++ runtime. If you use \l{How to Create Qt Plugins#Static Plugins}{static plugins}, then the
++ plugin code is already part of your application executable and no separate deployment steps
++ are required.
++
++ \section1 The Plugin Directory
++
++ In Qt, when an application starts, the application's executable directory is the base directory
++ where Qt searches for plugins.
++
++ For example, on Windows, if the application is in \c{C:\Program Files\MyApp} and it has a style
++ plugin, Qt looks in \c{C:\Program Files\MyApp\styles}.
++
++ To find out where your application's executable is located, see
++ QCoreApplication::applicationDirPath().
++
++ Qt also looks in the directory specified by QLibraryInfo::path(QLibraryInfo::PluginsPath),
++ which typically is located in \c QTDIR/plugins; \c QTDIR is the directory where Qt is installed.
++ If you want Qt to look in additional places you can add as many paths as you need with calls to
++ QCoreApplication::addLibraryPath(). If you want to set your own path(s), you can use
++ QCoreApplication::setLibraryPaths().
++
++ Alternatively, you can use a \c qt.conf file to override the hard-coded paths that are compiled
++ into the Qt library. For more information, see \l {Using qt.conf}.
++
++ Another possibility is to set the \c QT_PLUGIN_PATH environment variable before you run the
++ application; multiple paths can be separated with a system path separator. When set, Qt looks
++ for plugins in the paths specified in this variable.
++
++ \note Do not export \c QT_PLUGIN_PATH as a system-wide environment variable because it can
++ interfere with other Qt installations.
++
++ \section1 Loading and Verifying Plugins Dynamically
++
++ When loading plugins, the Qt library does some sanity checking to determine whether the plugin
++ can be loaded and used. This sanity check enables you to have multiple Qt versions and
++ configurations installed side by side.
++
++ The following rules apply:
++
++ \list
++ \li Plugins linked with a Qt library that has a higher minor version number will not be loaded by a
++ library with a lower minor version number.
++
++ \br
++ \b{Example:} Qt 6.2.0 will \e{not} load a plugin built with Qt 6.3.0.
++ \b{Example:} Qt 6.2.0 will load a plugin built with Qt 6.1.0.
++ \b{Example:} Qt 6.2.0 will load a plugin built with Qt 6.2.1.
++
++ \li Plugins linked with a Qt library that has a lower major version number will not be loaded
++ by a library with a higher major version number.
++
++ \br
++ \b{Example:} Qt 6.0.0 will \e{not} load a plugin built with Qt 5.15.0.
++ \endlist
++
++ When building plugins to extend an application, it's important to ensure that the plugin is
++ configured in the same way as the application. This means that if the application was built in
++ release mode, plugins should be built in release mode, too. Except for Unix operating systems,
++ where the plugin system will not load plugins built in a different mode from the application.
++
++ \section1 Debugging Plugins
++
++ There are a number of issues that may prevent correctly-written plugins from working with the
++ applications that are designed to use them. Many of these are related to differences in the way
++ that plugins and applications have been built, often arising from separate build systems and
++ processes.
++
++ To obtain diagnostic information from Qt, about each plugin it tries to load, use the
++ \c QT_DEBUG_PLUGINS environment variable. Set this variable to a non-zero value in the
++ environment where your application is launched.
++
++ The following table describes the common causes of problems developers experience when creating
++ plugins and possible solutions.
++
++ \table
++ \header
++ \li Problem \li Cause \li Solution
++ \row
++ \li Plugins silently fail to load even when opened directly by the application.
++ \QD shows the plugin libraries in its \uicontrol{Help|About Plugins} dialog, but no
++ plugins are listed under each of them.
++ \li The application and its plugins are built in different modes.
++ \li Build the plugin in the same configuration as the executable.
++ \endtable
++
++ */