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

QTextEdit, Qt

Content

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

Widget

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.

Widget.h

#ifndef WIDGET_H
#define WIDGET_H

#include <QWidget>

class SearchHighLight;

namespace Ui {
class Widget;
}

class Widget : public QWidget
{
    Q_OBJECT

public:
    explicit Widget(QWidget *parent = nullptr);
    ~Widget();

private:
    // 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

Widget.cpp

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

#include "SearchHighLight.h"

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

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

void Widget::onSearchText()
{
    // We load the text for search in syntax highlighting
    m_searchHighLight->searchText(ui->lineEdit->text());
}

SearchHightLight

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

SearchHightLight.h

#ifndef SEARCHHIGHLIGHT_H
#define SEARCHHIGHLIGHT_H

#include <QSyntaxHighlighter>
#include <QRegularExpression>

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

    void searchText(const QString& text);

protected:
    virtual void highlightBlock(const QString &text) override;

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

#endif // SEARCHHIGHLIGHT_H

SearchHightLight.cpp

#include "SearchHighLight.h"

#include <QTextCharFormat>

SearchHighLight::SearchHighLight(QTextDocument* parent) : BaseClass(parent)
{
    // Set the backlight color
    m_format.setBackground(Qt::green);
}

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
}

Conclusion

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

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April 7, 2020, 9:15 a.m.
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Last comments
K
April 7, 2020, 8:55 a.m.
KULINAR847

А вот уже и на python... #!/usr/bin/env python# -'''- coding: utf-8 -'''-import sysfrom PySide2.QtWidgets import *from PySide2.QtQuick import *from PySide2.QtCore import *from PySide2.…
April 3, 2020, 8:06 a.m.
Konstantin Grudnitskiy

Я надеюсь вы уже разобрались в чем дело, но если вдруг нет, то проблема состоит в том, что вы пытаетесь запустить программу из интерпретатора питона. Файл main.py это уже готова…
April 3, 2020, 6:18 a.m.
Konstantin Grudnitskiy

>>> text = 'hello world'>>> ' '.join(word for word in text.split()[:-1])'hello'>>> def remove_last_word(text):... return text and ' '.join(word for word in text.s…
March 27, 2020, 2:40 p.m.
Evgenij Legotskoj

Добрый день. В конце пятой статьи скачать можете.
March 27, 2020, 2:28 p.m.
mkdir _

Здравствуйте, а можно, пожалуйста, ссылку на целые исходники, если есть?
Now discuss on the forum
s
April 6, 2020, 8:06 a.m.
shuric

Добрый день. Объясните пожалуйста ... ... допиливать стилевое оформление в прокси классе ... где именно копать ? В каком виртуальном методе лучше допиливать (если можно н…
April 6, 2020, 4:19 a.m.
Evgenij Legotskoj

Попробуй не переустанавливать материал, а просто менять цвет
April 5, 2020, 11:38 a.m.
Mihailll

Так работает windeployqt --qmldir E:\QTProject\testQmlAndCpp E:\test\build-testQmlAndCpp-Desktop_Qt_5_14_1_MinGW_32_bit-Release
April 5, 2020, 2:35 a.m.
Mihailll

Так работает console.log(textEmail.text) var str = textEmail.text; var n = str.search(/^((([0-9A-Za-z]{1}[-0-9A-z\.]{1,}[0-9A-Za-z]{1})|([0-9А-Яа-я]{1}[-0-9А-я\.]{1,}[…
April 3, 2020, 8:48 a.m.
Intruder

Евгений, добрый день. Спасибо!
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