Development/Tutorials/Introduction to Goya usage: Difference between revisions

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    {{TutorialBrowser|
    {{Archived}}


    series=Goya Framework|
    name=Introduction to the Goya Framework usage|
    pre=[http://mindview.net/Books/TICPP/ThinkingInCPP2e.html C++], [http://www.trolltech.com/products/qt/ Qt], [http://doc.trolltech.com/latest/model-view-programming.html Model/View Qt Framework], [[Getting_Started/Build/KDE4|KDE4 development environment]]|
    next=[[Development/Tutorials/Introduction to Goya usage 2]]
    |
    }}
    ==Abstract==
    ==Abstract==
    We are developing some component of our application using Model/View (check prerequisites). At some point on our development, we discover that we actually want to add widgets to our delegate, but the Model/View framework does not provide a powerful and integrated way of doing so. Here is where Goya comes to help out for this task.
    We are developing some component of our application using Model/View (check prerequisites). At some point on our development, we discover that we actually want to add widgets to our delegate, but the Model/View framework does not provide a powerful and integrated way of doing so. Here is where Goya comes to help out for this task.
    Line 15: Line 6:
    We could say Goya is a layer between the view and your delegate that draws widgets with the needed options and that seem to behave as if they were real widgets, but they are fake widgets after all.
    We could say Goya is a layer between the view and your delegate that draws widgets with the needed options and that seem to behave as if they were real widgets, but they are fake widgets after all.


    Goya is so nice mainly because it integrates pretty well with the Model/View design, and uses the Qt powerful signals and slots. Goya widgets will emit signals when something have happened to them, so you will be able to connect those signals to your app slots, and do fancy stuff without complex stuff.
    Goya is so nice mainly because it integrates pretty well with the Model/View design, and uses the Qt powerful signals and slots. Goya widgets will emit signals when something has happened to them, so you will be able to connect those signals to your app slots, and do fancy stuff without complex stuff.
    ==A Simple Example==
    ==A Simple Example==
    This example consists on a single window that will contain a list view. There will be pushbuttons only in the odd rows.
    This example consists on a single window that will contain a list view. There will be pushbuttons only in the odd rows.


    <code cppqt>
    <syntaxhighlight lang="cpp-qt">
    // Basic Goya includes
    // Basic Goya includes
    #include <goya/goya.h>
    #include <goya/kwidgetitemdelegate.h>
    #include <goya/pushbutton.h>


    // Basic Qt includes
    // Basic Qt includes
    Line 38: Line 28:
    #include <kicon.h>
    #include <kicon.h>


    // We define the model "MyModel" as a QStringListModel. In this very simple
    // This is our delegate, it has to inherit KWidgetItemDelegate which inherits
    // example, the class will only return strings, and the necessary widgets.
    // QAbstractItemDelegate. The delegate needs on its constructor first
    class MyModel
    // parameter a view, this is different to a regular QAbstractItemDelegate
         : public QStringListModel
    // because we need to install event filters in order to allow interaction
    // with the user.
    class MiDelegate
         : public KWidgetItemDelegate
    {
    {
         Q_OBJECT
         Q_OBJECT
    public:
    public:
         MyModel(QObject *parent = 0)
         MiDelegate(QAbstractItemView *itemView, QObject *parent = 0)
             : QStringListModel(parent)
             : KWidgetItemDelegate(itemView, parent)
         {
         {
            // We create a Goya pushbutton, this pushbutton will be shared by all
            // rows using it, so the memory impact for 1000 rows is the same as for
            // 1 row. Since all our rows will show the same information (that
            // meaning the pushbutton will show always "More information") we
            // initialize the values here, and all rows will reuse them. In a
            // slightly more complex example we can later see how to handle this
            // when rows want for instance a different text for the pushbutton, or
            // a different icon.
            button = new Goya::PushButton(0);
            button->setText("More Information");
            button->setIcon(KIcon("help-about"));
            button->setIconSize(QSize(16, 16));
            // Goya is able to "eat events". This means that the events that you
            // specify here won't be forwarded to the view. This is pretty helpful
            // because when you click on a button that is in a non-selected row
            // and the MouseButtonPress eat is enabled, the unselected row won't
            // be selected, because the button receives that event, and "eats" it.
            button->setEatEvents(QEvent::MouseButtonPress);
            button->setEatEvents(QEvent::MouseButtonRelease);
            button->setEatEvents(QEvent::MouseButtonDblClick);
            // We would like to connect to the clicked signal of the pushbutton.
            connect(button, SIGNAL(clicked(QModelIndex,const Goya::PushButton*)),
                    this, SLOT(slotClicked(QModelIndex)));
         }
         }


         virtual ~MyModel()
         virtual ~MiDelegate()
         {
         {
            delete button;
         }
         }


         virtual QVariant data(const QModelIndex &index, int role) const
         QList<QWidget*> createItemWidgets() const
         {
         {
             // Goya when asking for widgets asks with role WidgetRole. We teach
             return QList<QWidget*>() << new QPushButton();
            // our model on what to do on this case. In this particular model, we
            // will return an empty widget list for odd rows, and a single widget
            // (our pushbutton) for even rows.
            // If the role that we were asked for is not the WidgetRole, we just
            // expect QStringListModel to do the right thing.
            if (role == Goya::WidgetRole)
            {
                if (index.row() % 2)
                    return GOYA_EMPTY_WIDGET_LIST;
     
                return GOYA_WIDGET_LIST(button);
            }
     
            return QStringListModel::data(index, role);
         }
         }


    private:
         void initializeItemWidgets(const QList<QWidget*> widgets,
         Goya::PushButton *button;
                                  const QStyleOptionViewItem &option,
     
                                  const QModelIndex &index) const
    private Q_SLOTS:
        // This slot will be triggered when our pushbutton has been clicked. Note
        // that the signal has an index and even a Goya::PushButton* parameters.
        // In this case only with the index we are OK. On the messagebox we notify
        // the user which row button was clicked.
        void slotClicked(const QModelIndex &index)
         {
         {
             KMessageBox::information(0, "More information clicked on row " +
             QPushButton *button = static_cast<QPushButton*>(widgets.at(0));
                                    QString::number(index.row() + 1),
            button->setText("More Information");
                                    "Button clicked");
            button->setIcon(KIcon("help-about"));
        }
            button->setIconSize(QSize(16, 16));
    };


    // This is our delegate. It will perform custom painting, but this a very
            connect(button, SIGNAL(clicked(QModelIndex,const Goya::PushButton*)),
    // important part with Goya integration. The most important thing here is that
                    this, SLOT(slotClicked(QModelIndex)));
    // this delegate inherits Goya::Canvas, what inherits QAbstractItemDelegate.
    class MyDelegate
        : public Goya::Canvas
    {
    public:
        MyDelegate(QAbstractItemView *itemView, QObject *parent = 0)
            : Canvas(itemView, parent)
        {
        }
     
        virtual ~MyDelegate()
        {
        }
     
        // Goya asks for the position of widgets. In this method you should
        // specify where do you want widget to be placed. In a slightly more
        // complex example we will see later that you can also specify your
        // position not only in absolute terms, but relative to other Goya
        // widgets.
        QPoint widgetPosition(Goya::Widget *widget, const QStyleOption *option,
                              const QModelIndex &index) const
        {
            // We will be at the topLeft corner, with a small separation from the
            // limits of the delegate of font height, for example.
            return QPoint(option->fontMetrics.height(),
                          option->fontMetrics.height());
         }
         }


    Line 162: Line 80:
             }
             }


            // In this case we want to draw the string below the button. sizeHint
            // method from Canvas will return the united rect of all widgets in
            // that row. As we only have one, is the same as asking for
            // Canvas::widgetSize with the correct parameters.
             painter->drawText(option.fontMetrics.height() + option.rect.left(),
             painter->drawText(option.fontMetrics.height() + option.rect.left(),
                               option.fontMetrics.height() * 3 +  
                               option.fontMetrics.height() * 3 +  
                               Canvas::sizeHint(option, index).height() +  
                               Canvas::sizeHint(option, index).height() +
                               option.rect.top(),
                               option.rect.top(),
                               QString("This is the index in row number ") +  
                               QString("This is the index in row number ") +  
    Line 175: Line 89:
             painter->restore();
             painter->restore();


             // This is very important. Do not forget to ask Goya to paint,
             KWidgetItemDelegate::paintWidgets(painter, option, index);
            // because this is the method that will actually draw the widgets
            // onto your delegate.
            Canvas::paint(painter, option, index);
         }
         }


         QSize sizeHint(const QStyleOptionViewItem &option,
         QSize sizeHint() const
                      const QModelIndex &index) const
         {
         {
             Q_UNUSED(option);
             return QSize(600, 60);
            Q_UNUSED(index);
        }


            // As before, we use sizeHint, but there is no problem of using
    private Q_SLOTS:
            // widgetSize with the correct parameters.
        void slotClicked(const QModelIndex &index)
            QSize size = Canvas::sizeHint(option, index);
        {
     
             KMessageBox::information(0, "More information clicked on row " +  
             size.setWidth(size.width() + option.fontMetrics.height() * 4);
                                    QString::number(index.row() + 1),
            size.setHeight(size.height() + option.fontMetrics.height() * 4);
                                    "Button clicked");
     
            return size;
         }
         }
    };
    };
    Line 202: Line 110:
         KAboutData aboutData("goyatest",
         KAboutData aboutData("goyatest",
                             0,
                             0,
                             ki18n("Goya Simple Test "),
                             ki18n("Goya Test "),
                             "1.0",
                             "1.0",
                             ki18n("A test for the Goya Framework"),
                             ki18n("A test for the Goya subsystem"),
                             KAboutData::License_LGPL,
                             KAboutData::License_LGPL,
                             ki18n("(c) Rafael Fernández López, 2008"),
                             ki18n("(c) Rafael Fernández López, 2007"),
                             ki18n("A test for the Goya Framework"),
                             ki18n("A test for the Goya subsystem"),
                             "http://www.ereslibre.es",
                             "http://www.ereslibre.es",
                             "[email protected]");
                             "[email protected]");
    Line 221: Line 129:


         QListView *listView = new QListView();
         QListView *listView = new QListView();
         MyModel *model = new MyModel();
         listView->setSelectionMode(QAbstractItemView::ExtendedSelection);
         MyDelegate *delegate = new MyDelegate(listView);
        QStringListModel *model = new QStringListModel();
         MiDelegate *delegate = new MiDelegate(listView);
     
        QListView *listView2 = new QListView();
        listView2->setSelectionMode(QAbstractItemView::ExtendedSelection);
        QStringListModel *model2 = new QStringListModel();
        MiDelegate *delegate2 = new MiDelegate(listView2);


         model->insertColumn(0);
         model->insertColumn(0);
    Line 229: Line 143:
             model->insertRow(i);
             model->insertRow(i);
             model->setData(model->index(i, 0), QString::number(i));
             model->setData(model->index(i, 0), QString::number(i));
        }
        model2->insertColumn(0);
        for (int i = 0; i < 10; ++i)
        {
            model2->insertRow(i);
            model2->setData(model2->index(i, 0), QString::number(i));
         }
         }


    Line 235: Line 156:
         listView->setVerticalScrollMode(QListView::ScrollPerPixel);
         listView->setVerticalScrollMode(QListView::ScrollPerPixel);


        listView2->setModel(model2);
        listView2->setItemDelegate(delegate2);
        listView2->setVerticalScrollMode(QListView::ScrollPerPixel);
        layout->addWidget(new QPushButton("Above Button"));
         layout->addWidget(listView);
         layout->addWidget(listView);
        layout->addWidget(listView2);
        layout->addWidget(new QPushButton("Below Button"));


         widget->show();
         widget->show();
    Line 241: Line 169:
         return app.exec();
         return app.exec();
    }
    }
    </code>
     
    #include "main.moc"
    </syntaxhighlight>

    Latest revision as of 12:45, 31 May 2019


    This page has been archived
    The information on this page is outdated or no longer in use but is kept for historical purposes. Please see the Category:Archives for similar pages.

    Abstract

    We are developing some component of our application using Model/View (check prerequisites). At some point on our development, we discover that we actually want to add widgets to our delegate, but the Model/View framework does not provide a powerful and integrated way of doing so. Here is where Goya comes to help out for this task.

    We could say Goya is a layer between the view and your delegate that draws widgets with the needed options and that seem to behave as if they were real widgets, but they are fake widgets after all.

    Goya is so nice mainly because it integrates pretty well with the Model/View design, and uses the Qt powerful signals and slots. Goya widgets will emit signals when something has happened to them, so you will be able to connect those signals to your app slots, and do fancy stuff without complex stuff.

    A Simple Example

    This example consists on a single window that will contain a list view. There will be pushbuttons only in the odd rows.

    // Basic Goya includes
    #include <goya/kwidgetitemdelegate.h>
    
    // Basic Qt includes
    #include <QPainter>
    #include <QBoxLayout>
    #include <QListView>
    #include <QStringListModel>
    
    // Basic KDE includes
    #include <kapplication.h>
    #include <kaboutdata.h>
    #include <kmessagebox.h>
    #include <kcmdlineargs.h>
    #include <klocalizedstring.h>
    #include <kicon.h>
    
    // This is our delegate, it has to inherit KWidgetItemDelegate which inherits
    // QAbstractItemDelegate. The delegate needs on its constructor first
    // parameter a view, this is different to a regular QAbstractItemDelegate
    // because we need to install event filters in order to allow interaction
    // with the user.
    class MiDelegate
        : public KWidgetItemDelegate
    {
        Q_OBJECT
    public:
        MiDelegate(QAbstractItemView *itemView, QObject *parent = 0)
            : KWidgetItemDelegate(itemView, parent)
        {
        }
    
        virtual ~MiDelegate()
        {
        }
    
        QList<QWidget*> createItemWidgets() const
        {
            return QList<QWidget*>() << new QPushButton();
        }
    
        void initializeItemWidgets(const QList<QWidget*> widgets,
                                   const QStyleOptionViewItem &option,
                                   const QModelIndex &index) const
        {
            QPushButton *button = static_cast<QPushButton*>(widgets.at(0));
            button->setText("More Information");
            button->setIcon(KIcon("help-about"));
            button->setIconSize(QSize(16, 16));
    
            connect(button, SIGNAL(clicked(QModelIndex,const Goya::PushButton*)),
                    this, SLOT(slotClicked(QModelIndex)));
        }
    
        void paint(QPainter *painter, const QStyleOptionViewItem &option,
                   const QModelIndex &index) const
        {
            if (option.state & QStyle::State_Selected)
            {
                painter->fillRect(option.rect, option.palette.highlight());
            }
    
            painter->save();
    
            if (option.state & QStyle::State_Selected)
            {
                painter->setPen(QPen(option.palette.highlightedText().color()));
            }
    
            painter->drawText(option.fontMetrics.height() + option.rect.left(),
                              option.fontMetrics.height() * 3 + 
                              Canvas::sizeHint(option, index).height() +
                              option.rect.top(),
                              QString("This is the index in row number ") + 
                              QString::number(index.row() + 1));
    
            painter->restore();
    
            KWidgetItemDelegate::paintWidgets(painter, option, index);
        }
    
        QSize sizeHint() const
        {
            return QSize(600, 60);
        }
    
    private Q_SLOTS:
        void slotClicked(const QModelIndex &index)
        {
            KMessageBox::information(0, "More information clicked on row " + 
                                     QString::number(index.row() + 1),
                                     "Button clicked");
        }
    };
    
    int main(int argc, char **argv)
    {
        KAboutData aboutData("goyatest",
                             0,
                             ki18n("Goya Test "),
                             "1.0",
                             ki18n("A test for the Goya subsystem"),
                             KAboutData::License_LGPL,
                             ki18n("(c) Rafael Fernández López, 2007"),
                             ki18n("A test for the Goya subsystem"),
                             "http://www.ereslibre.es",
                             "[email protected]");
    
        KCmdLineArgs::init(argc, argv, &aboutData);
        KApplication app;
    
        QWidget *widget = new QWidget();
        QVBoxLayout *layout = new QVBoxLayout;
    
        widget->setLayout(layout);
        widget->resize(800, 600);
    
        QListView *listView = new QListView();
        listView->setSelectionMode(QAbstractItemView::ExtendedSelection);
        QStringListModel *model = new QStringListModel();
        MiDelegate *delegate = new MiDelegate(listView);
    
        QListView *listView2 = new QListView();
        listView2->setSelectionMode(QAbstractItemView::ExtendedSelection);
        QStringListModel *model2 = new QStringListModel();
        MiDelegate *delegate2 = new MiDelegate(listView2);
    
        model->insertColumn(0);
        for (int i = 0; i < 1000; ++i)
        {
            model->insertRow(i);
            model->setData(model->index(i, 0), QString::number(i));
        }
    
        model2->insertColumn(0);
        for (int i = 0; i < 10; ++i)
        {
            model2->insertRow(i);
            model2->setData(model2->index(i, 0), QString::number(i));
        }
    
        listView->setModel(model);
        listView->setItemDelegate(delegate);
        listView->setVerticalScrollMode(QListView::ScrollPerPixel);
    
        listView2->setModel(model2);
        listView2->setItemDelegate(delegate2);
        listView2->setVerticalScrollMode(QListView::ScrollPerPixel);
    
        layout->addWidget(new QPushButton("Above Button"));
        layout->addWidget(listView);
        layout->addWidget(listView2);
        layout->addWidget(new QPushButton("Below Button"));
    
        widget->show();
    
        return app.exec();
    }
    
    #include "main.moc"