Using QML Modules with Plugins
QML modules may use plugins to expose components defined in C++ to QML applications. Qt Creator cannot load the plugins to determine the details of the contained components, and therefore, the modules must provide extra type information for code completion and the semantic checks to work correctly.
To create a QML module and make it appear in the Library in Qt Quick Designer:
- Create custom QML controls and place all the
.qml
files in a directory dedicated to your module. - Create a
qmldir
file for your module and place it in the module directory. For more information, see Module Definition qmldir Files. - Create a
qmltypes
file, preferably usingqmlplugindump
. For more information see, Generating qmltypes Files. - Create a directory named
designer
in your module directory. - Create a
.metainfo
file for your module and place it in thedesigner
directory. Meta information is needed to display the components in the QML Types tab in the Library. Use a metainfo file delivered with Qt, such asqtquickcontrols2.metainfo
, as an example. - Import your module into a project using
QML_IMPORT_PATH
in the .pro file:QML_IMPORT_PATH += path/to/module
. For more information, see Importing QML Modules. - Make sure that the QML emulation layer of Qt Quick Designer is built with the same Qt version as your QML modules. For more information, see Running QML Modules in Qt Quick Designer. You can also try skipping this step and take it later, if necessary.
Your module should now appear in the Imports tab in the Library in Qt Quick Designer. Your components should appear in the QML Types tab if a valid .metainfo
file is in place.
Registering QML Types
When you write a QML module or use QML from a C++ application, you typically register new types with the qmlRegisterType() function or expose some class instances with QQmlContext::setContextProperty(). The Qt Creator C++ code model now scans for these calls and tells the QML code model about them. This means that properties are displayed during code completion and the JavaScript code checker does not complain about unknown types. However, this works only when the source code is available, and therefore, you must explicitly generate type information for QML modules with plugins before distributing them.
Classes registered with qmlRegisterType()
can be used as backend objects in the Qt Quick Designer. For more information, see Adding Connections.
Generating qmltypes Files
Ideally, QML modules have a plugins.qmltypes
file in the same directory as the qmldir
file. The qmltypes
file contains a description of the types exported by the module's plugins and is loaded by Qt Creator when the module is imported.
For Qt 4.8 and later, one or more qmltypes
files can be listed in the qmldir
file under the typeinfo
header. These files will be read in addition to plugins.qmltypes
. For more information, see Writing a qmltypes File.
You can create and edit qmltypes
files manually, but you are recommended to use the qmlplugindump
tool shipped with Qt 4.8 and later to generate them automatically.
Once you have obtained qmlplugindump
for the Qt version the QML module's plugins were compiled with, run the following command to load My.Module version 1.0 from /import/path/my/module
including all its plugins and output a description of the plugins' types to /import/path/my/module/plugins.qmltypes
:
qmlplugindump -nonrelocatable My.Module 1.0 /import/path > /import/path/my/module/plugins.qmltypes
You can safely ignore the debug output.
For Qt 4.7.x, you can compile a version of the tool called qmldump
from the sources in <QtCreator>/share/qtcreator/qml/qmldump
if the Qt version contains private headers.
Dumping Plugins Automatically
If a module with plugins lacks the qmltypes
file, Qt Creator tries to generate a temporary file itself by running the qmldump
program in the background. However, this automatic dumping is a fallback mechanism with many points of failure and you cannot rely upon it.
Importing QML Modules
By default, Qt Creator will look in the QML import path of Qt for QML modules. If your applications adds additional import paths that Qt Creator should use, then you can specify those using QML_IMPORT_PATH
in the .pro
file of your application.
If you use CMake, add the following command to the CMakeLists.txt file to set the QML import path:
{set(QML_IMPORT_PATH ${CMAKE_SOURCE_DIR}/qml ${CMAKE_BINARY_DIR}/imports CACHE string "" FORCE)}
The import path affects all the targets built by the CMake project.
Running QML Modules in Qt Quick Designer
Qt Quick Designer uses a QML emulation layer (also called QML Puppet) to render and preview images and to collect data. To be able to render custom types correctly from QML modules, the emulation layer must be built with the same Qt version as the QML modules.
By default, a fallback emulation layer is provided by Qt Creator and built with the same Qt version as Qt Creator. Therefore, your QML modules will mostly not work out of the box.
To use an emulation layer that is built with the Qt configured in the build and run kit for the project, select Tools > Options > Qt Quick > Qt Quick Designer > Use QML emulation layer which is built by the selected Qt radio button. Qt Creator builds the emulation layer when you select the Design mode.
A plugin should behave differently depending on whether it is run by the emulation layer or an application. For example, animations should not be run in the Design mode. You can use the value of the QML_PUPPET_MODE environment variable to check whether the plugin is currently being run by an application or edited in the Design mode.
If you want to use a different module in Qt Quick Designer than in your actual application for example to mockup C++ items, then you can use QML_DESIGNER_IMPORT_PATH
in the .pro
file. Modules in the import paths defined in QML_DESIGNER_IMPORT_PATH
will be used only in Qt Quick Designer. For an example, see Qt Quick Controls 2 - Contact List.