source: trunk/src/gui/text/qsyntaxhighlighter.cpp

/****************************************************************************
**
** Copyright (C) 2011 Nokia Corporation and/or its subsidiary(-ies).
** All rights reserved.
** Contact: Nokia Corporation ([email protected])
**
** This file is part of the QtGui module of the Qt Toolkit.
**
** $QT_BEGIN_LICENSE:LGPL$
** Commercial Usage
** Licensees holding valid Qt Commercial licenses may use this file in
** accordance with the Qt Commercial License Agreement provided with the
** Software or, alternatively, in accordance with the terms contained in
** a written agreement between you and Nokia.
**
** GNU Lesser General Public License Usage
** Alternatively, this file may be used under the terms of the GNU Lesser
** General Public License version 2.1 as published by the Free Software
** Foundation and appearing in the file LICENSE.LGPL included in the
** packaging of this file.  Please review the following information to
** ensure the GNU Lesser General Public License version 2.1 requirements
** will be met: http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html.
**
** In addition, as a special exception, Nokia gives you certain additional
** rights.  These rights are described in the Nokia Qt LGPL Exception
** version 1.1, included in the file LGPL_EXCEPTION.txt in this package.
**
** GNU General Public License Usage
** Alternatively, this file may be used under the terms of the GNU
** General Public License version 3.0 as published by the Free Software
** Foundation and appearing in the file LICENSE.GPL included in the
** packaging of this file.  Please review the following information to
** ensure the GNU General Public License version 3.0 requirements will be
** met: http://www.gnu.org/copyleft/gpl.html.
**
** If you have questions regarding the use of this file, please contact
** Nokia at [email protected].
** $QT_END_LICENSE$
**
****************************************************************************/

#include "qsyntaxhighlighter.h"

#ifndef QT_NO_SYNTAXHIGHLIGHTER
#include <private/qobject_p.h>
#include <qtextdocument.h>
#include <private/qtextdocument_p.h>
#include <qtextlayout.h>
#include <qpointer.h>
#include <qtextobject.h>
#include <qtextcursor.h>
#include <qdebug.h>
#include <qtextedit.h>
#include <qtimer.h>

QT_BEGIN_NAMESPACE

class QSyntaxHighlighterPrivate : public QObjectPrivate
{
    Q_DECLARE_PUBLIC(QSyntaxHighlighter)
public:
    inline QSyntaxHighlighterPrivate()
        : rehighlightPending(false), inReformatBlocks(false)
    {}

    QPointer<QTextDocument> doc;

    void _q_reformatBlocks(int from, int charsRemoved, int charsAdded);
    void reformatBlocks(int from, int charsRemoved, int charsAdded);
    void reformatBlock(const QTextBlock &block);

    inline void rehighlight(QTextCursor &cursor, QTextCursor::MoveOperation operation) {
        inReformatBlocks = true;
        cursor.beginEditBlock();
        int from = cursor.position();
        cursor.movePosition(operation);
        reformatBlocks(from, 0, cursor.position() - from);
        cursor.endEditBlock();
        inReformatBlocks = false;
    }

    inline void _q_delayedRehighlight() {
        if (!rehighlightPending)
            return;
        rehighlightPending = false;
        q_func()->rehighlight();
    }

    void applyFormatChanges();
    QVector<QTextCharFormat> formatChanges;
    QTextBlock currentBlock;
    bool rehighlightPending;
    bool inReformatBlocks;
};

void QSyntaxHighlighterPrivate::applyFormatChanges()
{
    bool formatsChanged = false;

    QTextLayout *layout = currentBlock.layout();

    QList<QTextLayout::FormatRange> ranges = layout->additionalFormats();

    const int preeditAreaStart = layout->preeditAreaPosition();
    const int preeditAreaLength = layout->preeditAreaText().length();

    if (preeditAreaLength != 0) {
        QList<QTextLayout::FormatRange>::Iterator it = ranges.begin();
        while (it != ranges.end()) {
            if (it->start >= preeditAreaStart
                && it->start + it->length <= preeditAreaStart + preeditAreaLength) {
                ++it;
            } else {
                it = ranges.erase(it);
                formatsChanged = true;
            }
        }
    } else if (!ranges.isEmpty()) {
        ranges.clear();
        formatsChanged = true;
    }

    QTextCharFormat emptyFormat;

    QTextLayout::FormatRange r;
    r.start = -1;

    int i = 0;
    while (i < formatChanges.count()) {

        while (i < formatChanges.count() && formatChanges.at(i) == emptyFormat)
            ++i;

        if (i >= formatChanges.count())
            break;

        r.start = i;
        r.format = formatChanges.at(i);

        while (i < formatChanges.count() && formatChanges.at(i) == r.format)
            ++i;

        if (i >= formatChanges.count())
            break;

        r.length = i - r.start;

        if (preeditAreaLength != 0) {
            if (r.start >= preeditAreaStart)
                r.start += preeditAreaLength;
            else if (r.start + r.length >= preeditAreaStart)
                r.length += preeditAreaLength;
        }

        ranges << r;
        formatsChanged = true;
        r.start = -1;
    }

    if (r.start != -1) {
        r.length = formatChanges.count() - r.start;

        if (preeditAreaLength != 0) {
            if (r.start >= preeditAreaStart)
                r.start += preeditAreaLength;
            else if (r.start + r.length >= preeditAreaStart)
                r.length += preeditAreaLength;
        }

        ranges << r;
        formatsChanged = true;
    }

    if (formatsChanged) {
        layout->setAdditionalFormats(ranges);
        doc->markContentsDirty(currentBlock.position(), currentBlock.length());
    }
}

void QSyntaxHighlighterPrivate::_q_reformatBlocks(int from, int charsRemoved, int charsAdded)
{
    if (!inReformatBlocks)
        reformatBlocks(from, charsRemoved, charsAdded);
}

void QSyntaxHighlighterPrivate::reformatBlocks(int from, int charsRemoved, int charsAdded)
{
    rehighlightPending = false;

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

    int endPosition;
    QTextBlock lastBlock = doc->findBlock(from + charsAdded + (charsRemoved > 0 ? 1 : 0));
    if (lastBlock.isValid())
        endPosition = lastBlock.position() + lastBlock.length();
    else
        endPosition = doc->docHandle()->length();

    bool forceHighlightOfNextBlock = false;

    while (block.isValid() && (block.position() < endPosition || forceHighlightOfNextBlock)) {
        const int stateBeforeHighlight = block.userState();

        reformatBlock(block);

        forceHighlightOfNextBlock = (block.userState() != stateBeforeHighlight);

        block = block.next();
    }

    formatChanges.clear();
}

void QSyntaxHighlighterPrivate::reformatBlock(const QTextBlock &block)
{
    Q_Q(QSyntaxHighlighter);

    Q_ASSERT_X(!currentBlock.isValid(), "QSyntaxHighlighter::reformatBlock()", "reFormatBlock() called recursively");

    currentBlock = block;

    formatChanges.fill(QTextCharFormat(), block.length() - 1);
    q->highlightBlock(block.text());
    applyFormatChanges();

    currentBlock = QTextBlock();
}

/*!
    \class QSyntaxHighlighter
    \reentrant

    \brief The QSyntaxHighlighter class allows you to define syntax
    highlighting rules, and in addition you can use the class to query
    a document's current formatting or user data.

    \since 4.1

    \ingroup richtext-processing

    The QSyntaxHighlighter class is a base class for implementing
    QTextEdit syntax highlighters.  A syntax highligher automatically
    highlights parts of the text in a QTextEdit, or more generally in
    a QTextDocument. Syntax highlighters are often used when the user
    is entering text in a specific format (for example source code)
    and help the user to read the text and identify syntax errors.

    To provide your own syntax highlighting, you must subclass
    QSyntaxHighlighter and reimplement highlightBlock().

    When you create an instance of your QSyntaxHighlighter subclass,
    pass it the QTextEdit or QTextDocument that you want the syntax
    highlighting to be applied to. For example:

    \snippet doc/src/snippets/code/src_gui_text_qsyntaxhighlighter.cpp 0

    After this your highlightBlock() function will be called
    automatically whenever necessary. Use your highlightBlock()
    function to apply formatting (e.g. setting the font and color) to
    the text that is passed to it. QSyntaxHighlighter provides the
    setFormat() function which applies a given QTextCharFormat on
    the current text block. For example:

    \snippet doc/src/snippets/code/src_gui_text_qsyntaxhighlighter.cpp 1

    Some syntaxes can have constructs that span several text
    blocks. For example, a C++ syntax highlighter should be able to
    cope with \c{/}\c{*...*}\c{/} multiline comments. To deal with
    these cases it is necessary to know the end state of the previous
    text block (e.g. "in comment").

    Inside your highlightBlock() implementation you can query the end
    state of the previous text block using the previousBlockState()
    function. After parsing the block you can save the last state
    using setCurrentBlockState().

    The currentBlockState() and previousBlockState() functions return
    an int value. If no state is set, the returned value is -1. You
    can designate any other value to identify any given state using
    the setCurrentBlockState() function. Once the state is set the
    QTextBlock keeps that value until it is set set again or until the
    corresponding paragraph of text is deleted.

    For example, if you're writing a simple C++ syntax highlighter,
    you might designate 1 to signify "in comment":

    \snippet doc/src/snippets/code/src_gui_text_qsyntaxhighlighter.cpp 2

    In the example above, we first set the current block state to
    0. Then, if the previous block ended within a comment, we higlight
    from the beginning of the current block (\c {startIndex =
    0}). Otherwise, we search for the given start expression. If the
    specified end expression cannot be found in the text block, we
    change the current block state by calling setCurrentBlockState(),
    and make sure that the rest of the block is higlighted.