How to Draw Text & Line in Qt5 with QPainter

In this Qt5 article i want to show you How to Draw Text & Line in Qt5 with QPainter , The QPainter class performs low-level painting on widgets and other paint devices. QPainter provides highly optimized functions to do most of the drawing GUI programs require. It can draw everything from simple lines to complex shapes like pies and chords. It can also draw aligned text and pixmaps. Normally, it draws in a “natural” coordinate system, but it can also do view and world transformation. QPainter can operate on any object that inherits the QPaintDevice class. The common use of QPainter is inside a widget’s paint event: Construct and customize (e.g. set the pen or the brush) the painter. Then draw. Remember to destroy the QPainter object after drawing.

For example:

void SimpleExampleWidget::paintEvent(QPaintEvent *)
{
    QPainter painter(this);
    painter.setPen(Qt::blue);
    painter.setFont(QFont("Arial", 30));
    painter.drawText(rect(), Qt::AlignCenter, "Qt");
}

void SimpleExampleWidget::paintEvent(QPaintEvent *)

{

QPainter painter(this);

painter.setPen(Qt::blue);

painter.setFont(QFont("Arial", 30));

painter.drawText(rect(), Qt::AlignCenter, "Qt");

}

The core functionality of QPainter is drawing, but the class also provide several functions that allows you to customize QPainter’s settings and its rendering quality, and others that enable clipping. In addition you can control how different shapes are merged together by specifying the painter’s composition mode.

So first of all you need to create a New Project in Qt5 framework, after that open your mainwindow.h and add this header file

#include<QPainter>
#include<QTextDocument>

1 2	#include<QPainter> #include<QTextDocument>

Also in your mainwindow.h you need to write the paintEvent() method of QPainter class in the public section of the class

virtual void paintEvent(QPaintEvent *event);

1	virtual void paintEvent(QPaintEvent *event);

After adding your mainwindow.h will looks like this

#ifndef MAINWINDOW_H
#define MAINWINDOW_H

#include <QMainWindow>

#include<QPainter>
#include<QTextDocument>

namespace Ui {
class MainWindow;
}

class MainWindow : public QMainWindow
{
    Q_OBJECT

public:
    explicit MainWindow(QWidget *parent = 0);
    ~MainWindow();

    virtual void paintEvent(QPaintEvent *event);



private:
    Ui::MainWindow *ui;
};

#endif // MAINWINDOW_H

#ifndef MAINWINDOW_H

#define MAINWINDOW_H

#include <QMainWindow>

#include<QPainter>

#include<QTextDocument>

namespace Ui {

class MainWindow;

}

class MainWindow : public QMainWindow

{

Q_OBJECT

public:

explicit MainWindow(QWidget *parent = 0);

~MainWindow();

virtual void paintEvent(QPaintEvent *event);

private:

Ui::MainWindow *ui;

};

#endif // MAINWINDOW_H

So after that you need to add the paintEvent() definition in mainwindow.cpp and add the code for drawing texts

void MainWindow::paintEvent(QPaintEvent *event)
{
    //Drawing Texts

    QPainter mytext(this);
    mytext.setFont(QFont("Times", 16, QFont::Bold));
    mytext.drawText(QPoint(20,30), "Qt5 Text Drawing");


    // Giving Style To Texts


    QTextDocument document;
    QRect rect(0,0,250,250 );
    mytext.translate(100,50);

    document.setHtml("<b>Hello</b><font color='red' size='30'>Qt5 C++ </font>");
    document.drawContents(&mytext, rect);






}

void MainWindow::paintEvent(QPaintEvent *event)

{

//Drawing Texts

QPainter mytext(this);

mytext.setFont(QFont("Times", 16, QFont::Bold));

mytext.drawText(QPoint(20,30), "Qt5 Text Drawing");

// Giving Style To Texts

QTextDocument document;

QRect rect(0,0,250,250 );

mytext.translate(100,50);

document.setHtml("HelloQt5 C++ ");

document.drawContents(&mytext, rect);

}

After adding your mainwindow.cpp will be like this

#include "mainwindow.h"
#include "ui_mainwindow.h"


MainWindow::MainWindow(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::MainWindow)
{
    ui->setupUi(this);
}

MainWindow::~MainWindow()
{
    delete ui;
}

void MainWindow::paintEvent(QPaintEvent *event)
{
    //Drawing Texts

    QPainter mytext(this);
    mytext.setFont(QFont("Times", 16, QFont::Bold));
    mytext.drawText(QPoint(20,30), "Qt5 Text Drawing");


    // Giving Style To Texts


    QTextDocument document;
    QRect rect(0,0,250,250 );
    mytext.translate(100,50);

    document.setHtml("<b>Hello</b><font color='red' size='30'>Qt5 C++ </font>");
    document.drawContents(&mytext, rect);






}

#include "mainwindow.h"

#include "ui_mainwindow.h"

MainWindow::MainWindow(QWidget *parent) :

QMainWindow(parent),

ui(new Ui::MainWindow)

{

ui->setupUi(this);

}

MainWindow::~MainWindow()

{

delete ui;

}

void MainWindow::paintEvent(QPaintEvent *event)

{

//Drawing Texts

QPainter mytext(this);

mytext.setFont(QFont("Times", 16, QFont::Bold));

mytext.drawText(QPoint(20,30), "Qt5 Text Drawing");

// Giving Style To Texts

QTextDocument document;

QRect rect(0,0,250,250 );

mytext.translate(100,50);

document.setHtml("HelloQt5 C++ ");

document.drawContents(&mytext, rect);

}

So in the definition of the method we draw our text and also we have given html styles using QTextDocument

QTextDocument

QTextDocument is a container for structured rich text documents, providing support for styled text and various types of document elements, such as lists, tables, frames, and images. They can be created for use in a QTextEdit, or used independently.

Each document element is described by an associated format object. Each format object is treated as a unique object by QTextDocuments, and can be passed to objectForFormat() to obtain the document element that it is applied to.