highlighter.cpp Example File
^{richtext/syntaxhighlighter/highlighter.cpp}

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    **
    ** Copyright (C) 2005-2005 Trolltech AS. All rights reserved.
    **
    ** This file is part of the documentation of the Qt Toolkit.
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** License version 2.0 as published by the Free Software Foundation
** and appearing in the file LICENSE.GPL included in the packaging of
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    #include <QtGui>

    #include "highlighter.h"

    Highlighter::Highlighter(QObject *parent)
        : QObject(parent)
    {
    }

    void Highlighter::addToDocument(QTextDocument *doc)
    {
        connect(doc, SIGNAL(contentsChange(int, int, int)),
                this, SLOT(highlight(int, int, int)));
    }

    void Highlighter::addMapping(const QString &pattern,
                                 const QTextCharFormat &format)
    {
        mappings[pattern] = format;
    }

    void Highlighter::highlight(int position, int removed, int added)
    {
        QTextDocument *doc = qobject_cast<QTextDocument *>(sender());

        QTextBlock block = doc->findBlock(position);
        if (!block.isValid())
            return;

        QTextBlock endBlock;
        if (added > removed)
            endBlock = doc->findBlock(position + added);
        else
            endBlock = block;

        while (block.isValid() && !(endBlock < block)) {
            highlightBlock(block);
            block = block.next();
        }
    }

    void Highlighter::highlightBlock(QTextBlock block)
    {
        QTextLayout *layout = block.layout();
        const QString text = block.text();

        QList<QTextLayout::FormatRange> overrides;

        foreach (QString pattern, mappings.keys()) {
            QRegExp expression(pattern);
            int i = text.indexOf(expression);
            while (i >= 0) {
                QTextLayout::FormatRange range;
                range.start = i;
                range.length = expression.matchedLength();
                range.format = mappings[pattern];
                overrides << range;

                i = text.indexOf(expression, i + expression.matchedLength());
            }
        }

        layout->setAdditionalFormats(overrides);
        const_cast<QTextDocument *>(block.document())->markContentsDirty(
            block.position(), block.length());
    }