Syntax Highlighter Example


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  #include "highlighter.h"

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

      keywordFormat.setForeground(Qt::darkBlue);
      keywordFormat.setFontWeight(QFont::Bold);
      const QString keywordPatterns[] = {
          QStringLiteral("\\bchar\\b"), QStringLiteral("\\bclass\\b"), QStringLiteral("\\bconst\\b"),
          QStringLiteral("\\bdouble\\b"), QStringLiteral("\\benum\\b"), QStringLiteral("\\bexplicit\\b"),
          QStringLiteral("\\bfriend\\b"), QStringLiteral("\\binline\\b"), QStringLiteral("\\bint\\b"),
          QStringLiteral("\\blong\\b"), QStringLiteral("\\bnamespace\\b"), QStringLiteral("\\boperator\\b"),
          QStringLiteral("\\bprivate\\b"), QStringLiteral("\\bprotected\\b"), QStringLiteral("\\bpublic\\b"),
          QStringLiteral("\\bshort\\b"), QStringLiteral("\\bsignals\\b"), QStringLiteral("\\bsigned\\b"),
          QStringLiteral("\\bslots\\b"), QStringLiteral("\\bstatic\\b"), QStringLiteral("\\bstruct\\b"),
          QStringLiteral("\\btemplate\\b"), QStringLiteral("\\btypedef\\b"), QStringLiteral("\\btypename\\b"),
          QStringLiteral("\\bunion\\b"), QStringLiteral("\\bunsigned\\b"), QStringLiteral("\\bvirtual\\b"),
          QStringLiteral("\\bvoid\\b"), QStringLiteral("\\bvolatile\\b"), QStringLiteral("\\bbool\\b")
      };
      for (const QString &pattern : keywordPatterns) {
          rule.pattern = QRegularExpression(pattern);
          rule.format = keywordFormat;
          highlightingRules.append(rule);
      }

      classFormat.setFontWeight(QFont::Bold);
      classFormat.setForeground(Qt::darkMagenta);
      rule.pattern = QRegularExpression(QStringLiteral("\\bQ[A-Za-z]+\\b"));
      rule.format = classFormat;
      highlightingRules.append(rule);

      singleLineCommentFormat.setForeground(Qt::red);
      rule.pattern = QRegularExpression(QStringLiteral("//[^\n]*"));
      rule.format = singleLineCommentFormat;
      highlightingRules.append(rule);

      multiLineCommentFormat.setForeground(Qt::red);

      quotationFormat.setForeground(Qt::darkGreen);
      rule.pattern = QRegularExpression(QStringLiteral("\".*\""));
      rule.format = quotationFormat;
      highlightingRules.append(rule);

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

      commentStartExpression = QRegularExpression(QStringLiteral("/\\*"));
      commentEndExpression = QRegularExpression(QStringLiteral("\\*/"));
  }

  void Highlighter::highlightBlock(const QString &text)
  {
      for (const HighlightingRule &rule : qAsConst(highlightingRules)) {
          QRegularExpressionMatchIterator matchIterator = rule.pattern.globalMatch(text);
          while (matchIterator.hasNext()) {
              QRegularExpressionMatch match = matchIterator.next();
              setFormat(match.capturedStart(), match.capturedLength(), rule.format);
          }
      }
      setCurrentBlockState(0);

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

      while (startIndex >= 0) {
          QRegularExpressionMatch match = commentEndExpression.match(text, startIndex);
          int endIndex = match.capturedStart();
          int commentLength = 0;
          if (endIndex == -1) {
              setCurrentBlockState(1);
              commentLength = text.length() - startIndex;
          } else {
              commentLength = endIndex - startIndex
                              + match.capturedLength();
          }
          setFormat(startIndex, commentLength, multiLineCommentFormat);
          startIndex = text.indexOf(commentStartExpression, startIndex + commentLength);
      }
  }