Archived:Calculating text width in Qt

Article Metadata

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Tested with

Devices(s): Nokia 5800 XpressMusic

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Compatibility

Platform(s): S60 3rd Edition, FP1, FP2
S60 5th Edition

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Article

Keywords: QFontMetrics, QFont

Created: (29 Apr 2009)

Last edited: jimgilmour1 (30 Jun 2009)

Overview

This code snippets shows how to use the QFont and QFontMetrics classes to draw a string into the center of the screen and to get the string height and width in pixels.

Note: In order to use this code, you need to have Qt for S60 installed on your platform.

Preconditions

• Install latest Qt for S60 see Qt for S60 - Installation packages
• Check this link for installation guide: How to install the package.
• Go through this article: Getting started with Qt for S60

Source code

• This source code centers the text and sets the text colour.

void QMyWidget::paintEvent(QPaintEvent*)
    {
    QPainter painter(this);
 
    // Create font
    QFont f("Helvetica",6);
    // Set current font
    painter.setFont(f);
    // Set font color
    painter.setPen(Qt::white);
    // Get QFontMetrics reference
    QFontMetrics fm = painter.fontMetrics();
 
    QString text = "helloworld";
 
    // Calculate text center position into the screen using QFontMetrics class
    QPoint center = QPoint((widgetSize.width()-fm.width(text))/2,
                           fm.height());
 
    // QFontMetrics::width() gives calculated text width with current QFont in QPainter
    // QFontMetrics::height() gives text height
 
    painter.drawText(center,text);
    }

Postconditions

The text is centered on the screen.