使用Qt进行语法高亮（注释方式）

//语法高亮---QSyntaxHighlighter
//highlighter.h
class Highlighter : public QSyntaxHighlighter    //定义一个类继承自QSyntaxHightliaghter
{
    Q_OBJECT                                         //Qt宏定义

public:
    Highlighter(QTextDocument *parent = 0);      //构造函数，传递一个QTextDocument对象给其父类

protected:
    void highlightBlock(const QString &text) Q_DECL_OVERRIDE;    //块高亮使用的函数，自动调用

private:
    struct HighlightingRule                    //语法规则结构体，包含正则表达式模式串和匹配的样式
    {
        QRegExp pattern;
        QTextCharFormat format;
    };
    QVector<HighlightingRule> highlightingRules;    //规则的集合，可以定义多个高亮规则

    QRegExp commentStartExpression;                //注释的高亮，使用highliangBlock()匹配，下文提到
    QRegExp commentEndExpression;

    QTextCharFormat keywordFormat;                //高亮样式，关键词，一下顾名思义
    QTextCharFormat classFormat;
    QTextCharFormat singleLineCommentFormat;
    QTextCharFormat multiLineCommentFormat;
    QTextCharFormat quotationFormat;
    QTextCharFormat functionFormat;
};

//highlighter.c
#include "highlighter.h"

Highlighter::Highlighter(QTextDocument *parent)    //构造函数，主要是对词语的高亮
    : QSyntaxHighlighter(parent)
{
    HighlightingRule rule;                            //高亮规则

    keywordFormat.setForeground(Qt::darkBlue);    //设定关键词的高亮样式
    keywordFormat.setFontWeight(QFont::Bold);
    QStringList keywordPatterns;                    //关键词集合,关键都以正则表达式表示
    keywordPatterns << "\\bchar\\b" << "\\bclass\\b" << "\\bconst\\b"
                    << "\\bdouble\\b" << "\\benum\\b" << "\\bexplicit\\b"
                    << "\\bfriend\\b" << "\\binline\\b" << "\\bint\\b"
                    << "\\blong\\b" << "\\bnamespace\\b" << "\\boperator\\b"
                    << "\\bprivate\\b" << "\\bprotected\\b" << "\\bpublic\\b"
                    << "\\bshort\\b" << "\\bsignals\\b" << "\\bsigned\\b"
                    << "\\bslots\\b" << "\\bstatic\\b" << "\\bstruct\\b"
                    << "\\btemplate\\b" << "\\btypedef\\b" << "\\btypename\\b"
                    << "\\bunion\\b" << "\\bunsigned\\b" << "\\bvirtual\\b"
                    << "\\bvoid\\b" << "\\bvolatile\\b";
    foreach (const QString &pattern, keywordPatterns) {    //添加各个关键词到高亮规则中
        rule.pattern = QRegExp(pattern);
        rule.format = keywordFormat;
        highlightingRules.append(rule);
    }

    classFormat.setFontWeight(QFont::Bold);        //添加Qt的类到高亮规则中
    classFormat.setForeground(Qt::darkMagenta);
    rule.pattern = QRegExp("\\bQ[A-Za-z]+\\b");
    rule.format = classFormat;
    highlightingRules.append(rule);

    singleLineCommentFormat.setForeground(Qt::red);    //单行注释
    rule.pattern = QRegExp("//[^\n]*");
    rule.format = singleLineCommentFormat;
    highlightingRules.append(rule);

    multiLineCommentFormat.setForeground(Qt::red);    //多行注释，只设定了样式，具体匹配在highlightBlock中设置


    quotationFormat.setForeground(Qt::darkGreen);    //字符串
    rule.pattern = QRegExp("\".*\"");
    rule.format = quotationFormat;
    highlightingRules.append(rule);


    functionFormat.setFontItalic(true);        //函数
    functionFormat.setForeground(Qt::blue);
    rule.pattern = QRegExp("\\b[A-Za-z0-9_]+(?=\\()");
    rule.format = functionFormat;
    highlightingRules.append(rule);


    commentStartExpression = QRegExp("/\\*");        //多行注释的匹配正则表达式
    commentEndExpression = QRegExp("\\*/");
}


void Highlighter::highlightBlock(const QString &text)    //应用高亮规则，也用于区块的高亮，比如多行注释
{
    foreach (const HighlightingRule &rule, highlightingRules) {    //文本采用高亮规则
        QRegExp expression(rule.pattern);
        int index = expression.indexIn(text);
        while (index >= 0) {
            int length = expression.matchedLength();
            setFormat(index, length, rule.format);
            index = expression.indexIn(text, index + length);
        }
    }

    setCurrentBlockState(0);        //以下是多行注释的匹配

    int startIndex = 0;
    if (previousBlockState() != 1)
        startIndex = commentStartExpression.indexIn(text);

    while (startIndex >= 0) {
        int endIndex = commentEndExpression.indexIn(text, startIndex);
        int commentLength;
        if (endIndex == -1) {
            setCurrentBlockState(1);
            commentLength = text.length() - startIndex;
        } else {
            commentLength = endIndex - startIndex
                            + commentEndExpression.matchedLength();
        }
        setFormat(startIndex, commentLength, multiLineCommentFormat);
        startIndex = commentStartExpression.indexIn(text, startIndex + commentLength);
    }
}
//used in editor
void MainWindow::setupEditor()    
{
    QFont font;
    font.setFamily("Courier");
    font.setFixedPitch(true);
    font.setPointSize(10);

    editor = new QTextEdit;
    editor->setFont(font);

    highlighter = new Highlighter(editor->document());   //调用方法，新建对象并传递document

    QFile file("mainwindow.h");
    if (file.open(QFile::ReadOnly | QFile::Text))
        editor->setPlainText(file.readAll());
}