Difference between revisions of "Development/Tutorials/Writing Qt Designer Plugins"

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== Abstract ==
{{Note|This is now located at https://community.kde.org/Get_Involved/development/Tutorials/Writing_Qt_Designer_Plugins}}
This tutorial shows how to add support for custom GUI elements to Qt Designer. It starts by showing how to add a simple custom widget.
== Creating a simple factory for a custom widget ==
We assume you have written a nice widget which you also want to be able to use in Qt Designer and the ui files. For this to achieve you have to write a plugin module for Qt Designer. It consists of just a single object of a class you have to write.
=== The interface to the plugin ===
The class, a factory, needs to be subclassed from {{qt|QObject}} and to implement the interface {{qt|QDesignerCustomWidgetInterface}}, as given by example for the widget MyWidget in the "mywidgetdesignerfactory.h":
<code cppqt n>
// Qt
#include <QtDesigner/QDesignerCustomWidgetInterface>
class MyWidgetDesignerFactory : public QObject, public QDesignerCustomWidgetInterface
  Q_INTERFACES( QDesignerCustomWidgetInterface )
    explicit MyWidgetDesignerFactory : QObject* parent = 0 );
  public: // QDesignerCustomWidgetInterface API
    virtual QWidget* createWidget( QWidget* parent );
    virtual QString group() const;
    virtual QIcon icon() const;
    virtual QString includeFile() const;
    virtual bool isContainer() const;
    virtual QString name() const;
    virtual QString toolTip() const;
    virtual QString whatsThis() const;
=== Creating the data as needed by the interface  ===
The definition of the methods is done as shown in the file "mywidgetdesignerfactory.cpp":
<code cppqt n>
#include "mywidgetdesignerfactory.h"
// my lib
#include <mywidget.h>
// Qt
#include <QtCore/QtPlugin>
MyWidgetDesignerFactory::MyWidgetDesignerFactory( QObject* parent )
  : QObject( parent )
QWidget* MyWidgetDesignerFactory::createWidget( QWidget* parent )
    MyNamespace::MyWidget* widget = new MyNamespace::MyWidget( parent );
    // init with some example data useful in the preview inside Qt Designer
    // this data will be only used there, not in the resulting view in the program.
    return widget;
QString MyWidgetDesignerFactory::group() const
    return QString::fromLatin1("Some group (KDE)");
QIcon MyWidgetDesignerFactory::icon() const
    return QIcon();
QString MyWidgetDesignerFactory::includeFile() const
    return QString::fromLatin1("neededincludepathprefix/mywidget.h");
QString MyWidgetDesignerFactory::toolTip() const
    return QString::fromLatin1("Useful Widget of Mine");
QString MyWidgetDesignerFactory::whatsThis() const
    return QString::fromLatin1("Some description of my widget.");
bool MyWidgetDesignerFactory::isContainer() const
    return false;
QString MyWidgetDesignerFactory::name() const
    return QString::fromLatin1("MyNamespace::MyWidget");
// export macro, takes the name of the plugin module and the class name
Q_EXPORT_PLUGIN2( mydesignerplugin, MyWidgetDesignerFactory )
=== Adding to the Buildsystem ===
After you created the two files above you need to tell the buildsystem how to create the Qt Designer plugin and where to install it. This needs a CMakeLists.txt file in the same directory with such content:
set( mydesignerplugin_SRCS
# the name of the plugin module is the same name as used in the macro Q_EXPORT_PLUGIN2 in the mywidgetdesignerfactory.cpp file
kde4_add_plugin( mydesignerplugin  ${mydesignerplugin_SRCS} )
target_link_libraries( mydesignerplugin
  # other needed libs
install( TARGETS mydesignerplugin  DESTINATION ${PLUGIN_INSTALL_DIR}/plugins/designer )
=== Finding your widget in Qt Designer ===
If you successfully compiled and installed your plugin, (re-)start Qt Designer and have a look in the Widgetbox (on the left side by default). If everything worked perfectly you will see a new entry "MyNamespace::MyWidget" (as defined by MyWidgetDesignerFactory::name()) in the group "Some group (KDE)" (as defined by MyWidgetDesignerFactory::group()). Now drag and drop the entry to the currently edited view in Qt Designer, and voilà, it should be added to the view.

Latest revision as of 12:48, 16 May 2019

This page was last edited on 16 May 2019, at 12:48. Content is available under Creative Commons License SA 4.0 unless otherwise noted.