Evgenii Legotckoi
Evgenii LegotckoiDec. 13, 2018, 4:13 p.m.

Qt/C++ - Tutorial 088. Text search with highlighting in QTextEdit

In connection with a small question on the forum and slightly free time today. I will answer in the form of an article on how to highlight in QTextEdit all the words that need to be found in this text.

To implement this functionality, you will need to use QSyntaxHighighter , as if writing a syntax highlighting code. Here, by the way, is an example of syntax highlighting for HTML .

And here's an example.

Search text highlight

Project structure

Search Hightlight structure


The main application window is represented by a widget.

The widget class consists of several files.

  • Widget.ui
  • Widget.h
  • Widget.cpp

I will not go into details on how to build such a window in Qt Designer, but as a result of working with Qt Designer, you get the Widget.ui file.


#ifndef WIDGET_H
#define WIDGET_H

#include <QWidget>

class SearchHighLight;

namespace Ui {
class Widget;

class Widget : public QWidget

    explicit Widget(QWidget *parent = nullptr);

    // Slot to handle the pressing of the button to install the desired text
    void onSearchText();
    void onSearchText();

    Ui::Widget *ui;
    // Inherited class for creating syntax highlighting logic
    SearchHighLight* m_searchHighLight;

#endif // WIDGET_H


#include "Widget.h"
#include "ui_Widget.h"

#include "SearchHighLight.h"

Widget::Widget(QWidget *parent) :
    ui(new Ui::Widget)
    // Create and initialize search highlighting
    m_searchHighLight = new SearchHighLight(ui->textEdit->document());

    // We connect the signal of the button to the slots for calling the search.
    connect(ui->pushButton, &QPushButton::clicked, this, &Widget::onSearchText);

    delete ui;

void Widget::onSearchText()
    // We load the text for search in syntax highlighting


And now the most interesting thing is exactly how you can highlight text in a search using QSyntaxHighligher



#include <QSyntaxHighlighter>
#include <QRegularExpression>

class SearchHighLight : public QSyntaxHighlighter
    using BaseClass = QSyntaxHighlighter;
    explicit SearchHighLight(QTextDocument* parent = nullptr);

    void searchText(const QString& text);

    virtual void highlightBlock(const QString &text) override;

    QRegularExpression m_pattern; // Regular expression to search for, in our case, this word or text
    QTextCharFormat m_format;     // Text formatting, highlighting



#include "SearchHighLight.h"

#include <QTextCharFormat>

SearchHighLight::SearchHighLight(QTextDocument* parent) : BaseClass(parent)
    // Set the backlight color

void SearchHighLight::highlightBlock(const QString& text)
    // Using a regular expression, we find all matches.
    QRegularExpressionMatchIterator matchIterator = m_pattern.globalMatch(text);
    while (matchIterator.hasNext())
        // Highlight all matches
        QRegularExpressionMatch match = matchIterator.next();
        setFormat(match.capturedStart(), match.capturedLength(), m_format);

void SearchHighLight::searchText(const QString& text)
    // Set the text as a regular expression.
    m_pattern = QRegularExpression(text);
    rehighlight(); // Restart the backlight


And as a conclusion, a link to the Git repository with this example.

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