1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
|
/****************************************************************************
**
** Copyright (C) 2016 The Qt Company Ltd.
** Contact: https://www.qt.io/licensing/
**
** This file is part of the documentation of the Qt Toolkit.
**
** $QT_BEGIN_LICENSE:FDL$
** Commercial License Usage
** Licensees holding valid commercial Qt licenses may use this file in
** accordance with the commercial license agreement provided with the
** Software or, alternatively, in accordance with the terms contained in
** a written agreement between you and The Qt Company. For licensing terms
** and conditions see https://www.qt.io/terms-conditions. For further
** information use the contact form at https://www.qt.io/contact-us.
**
** GNU Free Documentation License Usage
** 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. Please review the following information to ensure
** the GNU Free Documentation License version 1.3 requirements
** will be met: https://www.gnu.org/licenses/fdl-1.3.html.
** $QT_END_LICENSE$
**
****************************************************************************/
/*!
\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::location(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 version number will not be loaded by a
library with a lower version number.
\br
\b{Example:} Qt 5.0.0 will \e{not} load a plugin built with Qt 5.0.1.
\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 5.0.1 will \e{not} load a plugin built with Qt 4.8.2.
\br
\b{Example:} Qt 5.1.1 will load plugins built with Qt 5.1.0 and Qt 5.0.3.
\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.
If you configure Qt to be built in both debug and release modes, but only build your
applications in release mode, you need to ensure that your plugins are also built in release
mode. By default, if a debug build of Qt is available, plugins will \e only be built in debug
mode. To force the plugins to be built in release mode, add the following line to the plugin's
project (\c{.pro}) file:
\code
CONFIG += release
\endcode
This ensures that the plugin is compatible with the version of the library used in 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 sliently 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 Either share the same build information or build the plugins in both debug and release
modes by appending the \c debug_and_release to the
\l{qmake Variable Reference#CONFIG}{CONFIG} variable in each of their project files.
\endtable
*/
|
