Archived:Calculating text width in Qt

Article Metadata

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Tested with

Devices(s): 5800 XpressMusic

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Compatibility

Platform(s): Qt

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Article

Keywords: QFontMetrics, QFont

Created: (26 Mar 2009)

Last edited: mind_freak (28 Mar 2009)

Overview

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

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

Preconditions

• Install Qt for S60 Garden release from here: Qt for S60 "Garden" pre-release
• Check this link for installation guide: How to install the package

Main Function

• Returns the width in pixels of the first len characters of text.

int pixelsWide = fm.width("What's the width of this text?");

• Return the height in pixel of the given string.

int pixelsHigh = fm.height();

Source Code

#include <QtGui/QApplication>
#include "lblfont.h"
#include<QWidget>
#include<QFormLayout>
#include<QPainter>
#include<QFont>
#include<QFontMetrics>
#include<QString>
#include<QLabel>
int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    QWidget *win=new QWidget();
    QFormLayout *lay=new QFormLayout();
    QFont f("Helvetica",6);
    QFontMetrics fm(f);
    int pixelsWide = fm.width("What's the width of this text?");
    int pixelsHigh = fm.height();
    QString str;
    QString str2;
    str=str.number(pixelsWide);
    str2=str2.number(pixelsHigh);
    QLabel *lbl=new QLabel();
    QLabel *lbl1=new QLabel();
    QLabel *lbl2=new QLabel("Text width in Pixels:");
    QLabel *lbl3=new QLabel("Text height in Pixels:");
    lbl->setText(str);
    lbl1->setText(str2);
    lay->addRow(lbl2,lbl);
    lay->addRow(lbl3,lbl1);
    win->setLayout(lay);
    win->show();
    return a.exec();
}

Screenshot

Source code

• This source code is use to set the text in center as well as to color the text.

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

Text is screen center.