QTextEdit之简单xml语法高亮

xml很多时候用来作为配置文件，有时为了方便在软件中查看编辑配置文件，需要一个简易的xml编辑器，qt没有提供xml语法高亮的例子，但是我们可以对着其他的例子改一个，下面是效果图：

xmlhighlighter.h:

#ifndef XMLHIGHLIGHTER_H
#define XMLHIGHLIGHTER_H

#include 
#include 

class XmlHighlighter : public QSyntaxHighlighter
{
    Q_OBJECT
public:
    explicit XmlHighlighter(QTextDocument *parent = nullptr);
protected:
    void highlightBlock(const QString &text);
signals:

public slots:
private:
    struct HighlightingRule
    {
        QRegExp pattern;
        QTextCharFormat format;
    };
    QVector<HighlightingRule> highlightingRules;

    QRegExp commentStartExpression;
    QRegExp commentEndExpression;
    
    QTextCharFormat multiLineCommentFormat;
    QTextCharFormat quotationFormat;
    QTextCharFormat elementNameFormat;
    QTextCharFormat propertyFormat;
};

#endif // XMLHIGHLIGHTER_H

xmlhighlighter.cpp:

#include "xmlhighlighter.h"

XmlHighlighter::XmlHighlighter(QTextDocument *parent) : QSyntaxHighlighter(parent)
{
    HighlightingRule rule;

    // 双引号
    quotationFormat.setForeground(Qt::blue);
    rule.pattern = QRegExp("\".*\"");
    rule.pattern.setMinimal(true); // 优先匹配最短的
    rule.format = quotationFormat;
    highlightingRules.append(rule);

    // 元素名
    propertyFormat.setForeground(Qt::red);
    rule.pattern = QRegExp("\\b[A-Za-z0-9_]+[\\s]*(?=\\=)");
    rule.pattern.setMinimal(true);
    rule.format = propertyFormat;
    highlightingRules.append(rule);

    // 元素名
    elementNameFormat.setForeground(Qt::blue);
    rule.pattern = QRegExp("<[\\/]*[A-Za-z0-9_]+\\b|>");
    rule.pattern.setMinimal(true);
    rule.format = elementNameFormat;
    highlightingRules.append(rule);

    // 多行注释
    multiLineCommentFormat.setForeground(Qt::darkGreen);
    commentStartExpression = QRegExp("");
}

void XmlHighlighter::highlightBlock(const QString &text)
{
    foreach (const HighlightingRule &rule, highlightingRules) {
        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);

    // 匹配多行注释
    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);
    }
}

调用：

ui->textEdit->setTabStopWidth(ui->textEdit->fontMetrics().width(' ')*4); // tab键设为4个空格的宽度
new XmlHighlighter(ui->textEdit->document());