Highlight All line in QTextBrowser

I use this code below to highlight the select text in text Browser.
the var selectLine have a text to highlight, but i want select all line width in editor with this text not just a selected text

Code:

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void MyHighlighter::highlightBlock(const QString &text)
 {
     QTextCharFormat myClassFormat;
     QColor  backColor = QColor("Red");
     myClassFormat.setBackground(backColor);
     myClassFormat.setProperty(QTextFormat::FullWidthSelection, true);
 
     QString pattern = selectLine;
 
     QRegExp expression(pattern);
     int index = text.indexOf(expression);
     while (index >= 0) {
         int length = expression.matchedLength();
         setFormat(index, length , myClassFormat);
         index = text.indexOf(expression, index + length);
     }
}
}

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how can I do IT?