Subscript text in painter->drawTExt(..)

[maverick_pol]

Hi,

I have used the subscript text while create a QGraphicsTextItem(using setHTML("_..."), but now I need to draw the subscript text using a painter.
Possibly I will use the painter->drawText(...), but how to construct a QString with a subscript text?

Thanks for any ideas.

Maverick

[jpn]

How about using QTextLayout?

[Uwe]

void drawRichText(QPainter *painter, const QRect &rect, int flags, QTextDocument &text)
{
    text.setPageSize(QSize(rect.width(), QWIDGETSIZE_MAX));
 
    QAbstractTextDocumentLayout* layout = text.documentLayout();
 
    const int height = qRound(layout->documentSize().height());
    int y = rect.y();
    if (flags & Qt::AlignBottom)
        y += (rect.height() - height);
    else if (flags & Qt::AlignVCenter)
        y += (rect.height() - height)/2;
 
    QAbstractTextDocumentLayout::PaintContext context;
    context.palette.setColor(QPalette::Text, painter->pen().color());
 
    painter->save();
 
    painter->translate(rect.x(), y);
    layout->draw(painter, context);
 
    painter->restore();
}

void drawRichText(QPainter *painter, const QRect &rect, int flags, QTextDocument &text)
{
    text.setPageSize(QSize(rect.width(), QWIDGETSIZE_MAX));

    QAbstractTextDocumentLayout* layout = text.documentLayout();

    const int height = qRound(layout->documentSize().height());
    int y = rect.y();
    if (flags & Qt::AlignBottom)
        y += (rect.height() - height);
    else if (flags & Qt::AlignVCenter)
        y += (rect.height() - height)/2;

    QAbstractTextDocumentLayout::PaintContext context;
    context.palette.setColor(QPalette::Text, painter->pen().color());

    painter->save();

    painter->translate(rect.x(), y);
    layout->draw(painter, context);

    painter->restore();
}

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If you need additional operations like heightForWidth() or textSize() you can have a look at the implementation of QwtRichTextEngine in the Qwt package.

And yes, you can ask yourself, why you have to write this strange code for such a simple task.

HTH,
Uwe

[maverick_pol]

Hi,

Thanks both of You! So what which solutions is better? Let's say I want to draw a text("upper _lower"at QPointF(10,10). How to use QTextlayout to do this? I am not quite sure.

Let's say that I set a var containing my text like this:

QTextDocument*   text = new QTextDocument(0);
    text->setHtml("upper<sub>lower</sub>");

QTextDocument*   text = new QTextDocument(0);
    text->setHtml("upper<sub>lower</sub>");

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and now I need to draw the text in QPointF(10,10);

Isn't there a simpler way than using your function Uwe? Just wondering.

Thanks.

Maverick

[Uwe]

Isn't there a simpler way than using your function Uwe?

My code always prints the labels into a rect. In your case you can skip the alignment lines and have to adopt it to paint to a position. But the basics of the code will remain as ugly as it is.

I guess Scribe is designed for implementing something big like an office package and maybe it's ok for this - I never wrote one myself. But for the use case of drawing simple rich text labels, almost nobody ( I also had to ask the TrollTech support and it's by far not the first time I'm posting this code) will find the right code on his own. For a product, that takes care of a clean API, this is a very surprising situation.

If you have a commercial license you could also have a look at the MathML renderer in the Qt solution package.

Uwe