Style Plugin Example

SimpleStylePlugin inherits https:// and is the plugin class.

class SimpleStylePlugin : public QStylePlugin
{
    Q_OBJECT
    Q_PLUGIN_METADATA(IID "org.qt-project.Qt.QStyleFactoryInterface" FILE "simplestyle.json")

public:
    SimpleStylePlugin() {}

    QStringList keys() const;
    QStyle *create(const QString &key) override;
};

keys() returns a list of style names that this plugin can create, while create() takes such a string and returns the https:// corresponding to the key. Both functions are pure virtual functions reimplemented from https://. When an application requests an instance of the SimpleStyle style, which this plugin creates, Qt will create it with this plugin.

Here is the implementation of keys():

QStringList SimpleStylePlugin::keys() const
{
    return QStringList() << "SimpleStyle";
}

Since this plugin only supports one style, we return a https:// with the class name of that style.

Here is the create() function:

QStyle *SimpleStylePlugin::create(const QString &key)
{
    if (key.toLower() == "simplestyle")
        return new SimpleStyle;
    return 0;
}

Note that the key for style plugins are case insensitive. The case sensitivity varies from plugin to plugin, so you need to check this when implementing new plugins.

int main(int argv, char *args[])
{
    QApplication app(argv, args);
    QApplication::setStyle(QStyleFactory::create("simplestyle"));

    StyleWindow window;
    window.resize(200, 50);
    window.show();

    return app.exec();
}

Qt loads the available style plugins when the https:// object is initialized. The https:// class knows about all styles and produces them with https://() (it is a wrapper around all the style plugins).

The SimpleStylePlugin lives in its own directory and have its own profile:

TEMPLATE    = lib
CONFIG     += plugin
QT         += widgets
HEADERS     = simplestyle.h \
              simplestyleplugin.h
SOURCES     = simplestyle.cpp \
              simplestyleplugin.cpp
TARGET      = simplestyleplugin

In the plugin profile we need to set the lib template as we are building a shared library instead of an executable. We must also set the config to plugin. We set the library to be stored in the styles folder under stylewindow because this is a path in which Qt will search for style plugins.

In addition to the plugin https://, we have other examples and articles that concern plugins.

In the https:// we show how to implement plugins that extends Qt applications rather than Qt itself, which is the case with the style plugin of this example. The https:// example shows how to implement a static plugin as well as being a more involved example on plugins that extend applications.

Files:

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