How to change text alignment in QTabWidget in C++?

Question

This is the same question as in: How to change text alignment in QTabWidget?

I tried to port that python code into C++ but it doesn't seem to work.

Here is header file:

#include <QTabBar>

class HorizontalTabWidget : public QTabBar
{
    Q_OBJECT
public:
    explicit HorizontalTabWidget(QWidget *parent = 0);

protected:
    void paintEvent(QPaintEvent *);
    QSize sizeHint() const;
};

Here is source file:

void HorizontalTabWidget::paintEvent(QPaintEvent *)
{
    for(int index = 0; index < count(); index++)
    {
        QPainter * painter = new QPainter(this);
        painter->begin(this);
        painter->setPen(Qt::blue);
        painter->setFont(QFont("Arial", 10));
        QRect tabrect = tabRect(index);
        painter->drawText(tabrect, Qt::AlignVCenter | Qt::TextDontClip, tabText(index));
        painter->end();
    }
}

QSize HorizontalTabWidget::sizeHint() const
{
    return QSize(130, 130);
}

I use it by creating NewTabWidget class that inherits QTabWidget. In the constructor of NewTabWidget I use:

setTabBar(new HorizontalTabWidget);

This is done just to be able to use that tabWidget because setTabBar is protected. Here is what I get:

What am I missing?

Edit: What I want to create is this but with icons on the top and the labels under the icons (as in Qt Creator):

Answer 1

the problem should be in the paint method; check if an example below would work for you, it should draw tabs the same way QTCreator does. I've reused the original tab style QStyleOptionTabV3 to do majority of paint work and then just rendered icon and tab's text on top of the image it produced:

class TestTabBar : public QTabBar
{
public:
    explicit TestTabBar(QWidget* parent=0) : QTabBar(parent)
    {
        setIconSize(QSize(80, 80));
    }

protected:
    QSize tabSizeHint(int) const
    {
        return QSize(80, 80);
    }
    void paintEvent(QPaintEvent *)
    {
        QStylePainter p(this);
        for (int index = 0; index < count(); index++)
        {
            QStyleOptionTabV3 tab;
            initStyleOption(&tab, index);

            QIcon tempIcon = tab.icon;
            QString tempText = tab.text;
            tab.icon = QIcon();
            tab.text = QString();

            p.drawControl(QStyle::CE_TabBarTab, tab);

            QPainter painter;
            painter.begin(this);
            QRect tabrect = tabRect(index);
            tabrect.adjust(0, 8, 0, -8);
            painter.drawText(tabrect, Qt::AlignBottom | Qt::AlignHCenter, tempText);
            tempIcon.paint(&painter, 0, tabrect.top(), tab.iconSize.width(), tab.iconSize.height(), Qt::AlignTop | Qt::AlignHCenter);    
            painter.end();
        }
    }
};

class TestTabWidget : public QTabWidget
{
public:
    explicit TestTabWidget(QWidget *parent = 0) : QTabWidget(parent)
    {
        setTabBar(new TestTabBar());
    }
};

tabwidget init:

TestTabWidget* test = new TestTabWidget(this);
test->setGeometry(20, 20, 300, 200);
test->addTab(new QWidget(), QIcon("icon0.png"), "test0");
test->addTab(new QWidget(), QIcon("icon1.png"), "test1");
test->setTabPosition(QTabWidget::West);

this worked fine on my ubuntu, hope it gonna work for you, regards

Answer 2

Vasiliy, thanks for fixing the double QPainter bug.

However, calling setTabIcon() and setTabText() from within paintEvent() leads to an infinite recursion. Remember that tab is a local object, so

tab.text = QString();

does not affect tabText().

So, the example can also be written without making temporary copies and do

p.drawText(tabrect, Qt::AlignBottom | Qt::AlignHCenter, tabText(index));
tabIcon(index).paint(&p, tabrect, Qt::AlignTop | Qt::AlignHCenter);

Answer 3

This example does not work. leads to a fall program.

bring your own example with minor edits - my system qt 4.6.3 for Windows and VS2008

class TestTabBar : public QTabBar
{
public:
    explicit TestTabBar(QWidget* parent=0) : QTabBar(parent)
    {
        setIconSize(QSize(58, 68));
    }

protected:
    QSize tabSizeHint(int) const
    {
        return QSize(58, 68);
    }

    void paintEvent(QPaintEvent *)
    {
        QStylePainter p(this);

        for (int index = 0; index < count(); index++)
        {
            QStyleOptionTabV3 tab;
            initStyleOption(&tab, index);

            QIcon tempIcon = tabIcon(index);
            QString tempText = this->tabText(index);

            QRect tabrect = tabRect(index);

            tab.icon = QIcon();
            tab.text = QString();

            p.drawControl(QStyle::CE_TabBarTab, tab);
            tabrect.adjust(0, 3, 0, -3);

            p.setPen(Qt::black);    
            p.setFont(QFont("Arial", 7));

            p.drawText(tabrect, Qt::AlignBottom | Qt::AlignHCenter, tempText );
            tempIcon.paint(&p, tabrect, Qt::AlignTop | Qt::AlignHCenter);

            this->setTabIcon(index, tempIcon );
            this->setTabText( index, tempText);
        }
    }
};

class TestTabWidget : public QTabWidget
{
public:
    explicit TestTabWidget(QWidget *parent = 0) : QTabWidget(parent)
    {
        setTabBar(new TestTabBar());
    }
};