Development/Tutorials/Introduction to Goya usage

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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"