Syntax highlighting of rich text

When we implement syntax highlighting Qt A class of its own , yes QSyntaxHighlighter Class implementation , When outputting words, search for keywords and set them to highlight .

Add new file ：

Customization files , take QSyntaxHighlighter As the base class  

MySyntaxHighlighter The header file ：

#ifndef MYSYNTAXHIGHLIGHTER_H
#define MYSYNTAXHIGHLIGHTER_H

#include<QSyntaxHighlighter>
class MySyntaxHighlighter : public QSyntaxHighlighter
{
    Q_OBJECT
public:
    MySyntaxHighlighter(QTextDocument* parent=0);
protected:
    void highlightBlock(const QString&text);
};

#endif // MYSYNTAXHIGHLIGHTER_H

Add meta objects Q_object, Add parameters QTextDocument* parent, Used to initialize the parent class .

Override the highlight function highlightBlock（）

MySyntaxHighlighter Source file ：

#include "mysyntaxhighlighter.h"

MySyntaxHighlighter::MySyntaxHighlighter(QTextDocument* parent):QSyntaxHighlighter(parent)
{

}

// Override the highlighting method 
void MySyntaxHighlighter::highlightBlock(const QString &text)
{
    QTextCharFormat format;// Define a character format 
    format.setFontWeight(QFont::Bold);
    format.setBackground(Qt::lightGray);
    format.setForeground(Qt::blue);

    QString pattern="\\bgood\\b";// take good As a keyword 
    QRegExp expression(pattern);
    int index=text.indexOf(expression);// Match text to expression , If it matches, it returns the position where the character appears , Return on no -1
    while(index>=0){
        int length=expression.matchedLength();// The length of the matched characters 
        setFormat(index,length,format);
        index=text.indexOf(expression,index+length);
    }
}

Highlight override , First set a character format object format, Further set the font format , After setting, define a string pattern matching good,\\b Represents the font boundary , I'll use it again QRegExp Define a regular expression object ,indexof Returns the first match to the specified subscript string , If there is no match, return -1 End the lecture . The highlight operation is still inseparable setFormat function .

stay mainwindow Add a member to the header file ：

  MySyntaxHighlighter *m_slighter;// Syntax highlighting objects 

 mainwindow Constructor adds code ：

  // Initialize highlighted objects 
    m_slighter=new MySyntaxHighlighter(ui->textEdit->document());

Highlight effect ：