qfontmetrics.cpp

qt-x11-opensource-src-4.1.4.tar.gz源码

    return qRound(engine->maxCharWidth());
}

/*!
    Returns the 'x' height of the font. This is often but not always
    the same as the height of the character 'x'.
*/
int QFontMetrics::xHeight() const
{
    QFontEngine *engine = d->engineForScript(QUnicodeTables::Common);
    Q_ASSERT(engine != 0);
    return qRound(engine->xHeight());
}

/*!
    Returns true if character \a ch is a valid character in the font;
    otherwise returns false.
*/
bool QFontMetrics::inFont(QChar ch) const
{
    const int script = QUnicodeTables::script(ch);
    QFontEngine *engine = d->engineForScript(script);
    Q_ASSERT(engine != 0);
    if (engine->type() == QFontEngine::Box)
        return false;
    return engine->canRender(&ch, 1);
}

/*! \fn int QFontMetrics::leftBearing(QChar ch) const
    Returns the left bearing of character \a ch in the font.

    The left bearing is the right-ward distance of the left-most pixel
    of the character from the logical origin of the character. This
    value is negative if the pixels of the character extend to the
    left of the logical origin.

    See width(QChar) for a graphical description of this metric.

    \sa rightBearing(), minLeftBearing(), width()
*/
int QFontMetrics::leftBearing(QChar ch) const
{
    const int script = QUnicodeTables::script(ch);
    QFontEngine *engine = d->engineForScript(script);
    Q_ASSERT(engine != 0);
    if (engine->type() == QFontEngine::Box)
        return 0;

    QGlyphLayout glyphs[10];
    int nglyphs = 9;
    engine->stringToCMap(&ch, 1, glyphs, &nglyphs, 0);
    // ### can nglyphs != 1 happen at all? Not currently I think
    glyph_metrics_t gi = engine->boundingBox(glyphs[0].glyph);
    return qRound(gi.x);
}

/*! \fn int QFontMetrics::rightBearing(QChar ch) const
    Returns the right bearing of character \a ch in the font.

    The right bearing is the left-ward distance of the right-most
    pixel of the character from the logical origin of a subsequent
    character. This value is negative if the pixels of the character
    extend to the right of the width() of the character.

    See width() for a graphical description of this metric.

    \sa leftBearing(), minRightBearing(), width()
*/
int QFontMetrics::rightBearing(QChar ch) const
{
    const int script = QUnicodeTables::script(ch);
    QFontEngine *engine = d->engineForScript(script);
    Q_ASSERT(engine != 0);
    if (engine->type() == QFontEngine::Box)
        return 0;

    QGlyphLayout glyphs[10];
    int nglyphs = 9;
    engine->stringToCMap(&ch, 1, glyphs, &nglyphs, 0);
    // ### can nglyphs != 1 happen at all? Not currently I think
    glyph_metrics_t gi = engine->boundingBox(glyphs[0].glyph);
    return qRound(gi.xoff - gi.x - gi.width);
}

/*!
    Returns the width in pixels of the first \a len characters of \a
    str. If \a len is negative (the default), the entire string is
    used.

    Note that this value is \e not equal to boundingRect().width();
    boundingRect() returns a rectangle describing the pixels this
    string will cover whereas width() returns the distance to where
    the next string should be drawn.

    \sa boundingRect()
*/
int QFontMetrics::width(const QString &str, int len) const
{
    if (len < 0)
        len = str.length();
    if (len == 0)
        return 0;

    QTextEngine layout(str, d);
    layout.ignoreBidi = true;
    layout.itemize();
    return qRound(layout.width(0, len));
}

/*! \fn int QFontMetrics::width(QChar ch) const

    \overload

    \img bearings.png Bearings

    Returns the logical width of character \a ch in pixels. This is a
    distance appropriate for drawing a subsequent character after \a
    ch.

    Some of the metrics are described in the image to the right. The
    central dark rectangles cover the logical width() of each
    character. The outer pale rectangles cover the leftBearing() and
    rightBearing() of each character. Notice that the bearings of "f"
    in this particular font are both negative, while the bearings of
    "o" are both positive.

    \warning This function will produce incorrect results for Arabic
    characters or non-spacing marks in the middle of a string, as the
    glyph shaping and positioning of marks that happens when
    processing strings cannot be taken into account. Use charWidth()
    instead if you aren't looking for the width of isolated
    characters.

    \sa boundingRect(), charWidth()
*/
int QFontMetrics::width(QChar ch) const
{
    if (::category(ch) == QChar::Mark_NonSpacing)
        return 0;

    const int script = QUnicodeTables::script(ch);
    QFontEngine *engine = d->engineForScript(script);
    Q_ASSERT(engine != 0);

    QGlyphLayout glyphs[8];
    int nglyphs = 7;
    engine->stringToCMap(&ch, 1, glyphs, &nglyphs, 0);
    return qRound(glyphs[0].advance.x);
}

/*!
    Returns the width of the character at position \a pos in the
    string \a str.

    The whole string is needed, as the glyph drawn may change
    depending on the context (the letter before and after the current
    one) for some languages (e.g. Arabic).

    This function also takes non spacing marks and ligatures into
    account.
*/
int QFontMetrics::charWidth(const QString &str, int pos) const
{
    if (pos < 0 || pos > (int)str.length())
        return 0;

    const QChar &ch = str.unicode()[pos];
    const int script = QUnicodeTables::script(ch);
    int width;

    if (script != QUnicodeTables::Common) {
        // complex script shaping. Have to do some hard work
        int from = qMax(0, pos - 8);
        int to = qMin((int)str.length(), pos + 8);
        QString cstr = QString::fromRawData(str.unicode()+from, to-from);
        QTextEngine layout(cstr, d);
        layout.ignoreBidi = true;
        layout.itemize();
        width = qRound(layout.width(pos-from, 1));
    } else if (::category(ch) == QChar::Mark_NonSpacing) {
        width = 0;
    } else {
        QFontEngine *engine = d->engineForScript(script);
        Q_ASSERT(engine != 0);

        QGlyphLayout glyphs[8];
        int nglyphs = 7;
        engine->stringToCMap(&ch, 1, glyphs, &nglyphs, 0);
        width = qRound(glyphs[0].advance.x);
    }
    return width;
}

/*!
    Returns the bounding rectangle of the characters in the string
    specified by \a str, which is the set of pixels the text would
    cover if drawn at (0, 0).

    Note that the bounding rectangle may extend to the left of (0, 0),
    e.g. for italicized fonts, and that the text output may cover \e
    all pixels in the bounding rectangle.

    Newline characters are processed as normal characters, \e not as
    linebreaks.

    Due to the different actual character heights, the height of the
    bounding rectangle of e.g. "Yes" and "yes" may be different.

    \sa width(), QPainter::boundingRect()
*/
QRect QFontMetrics::boundingRect(const QString &str) const
{
    if (str.length() == 0)
        return QRect();

    QTextEngine layout(str, d);
    layout.ignoreBidi = true;
    layout.itemize();
    glyph_metrics_t gm = layout.boundingBox(0, str.length());
    return QRect(qRound(gm.x), qRound(gm.y), qRound(gm.width), qRound(gm.height));
}

/*!
    Returns the rectangle that is covered by ink if the character where
    to be drawn at the origin of the coordinate system.

    Note that the bounding rectangle may extend to the left of (0, 0),
    e.g. for italicized fonts, and that the text output may cover \e
    all pixels in the bounding rectangle. For a space character the rectangle
    will usually be empty.

    Note that the rectangle usually extends both above and below the
    base line.

    \warning The width of the returned rectangle is not the advance width
    of the character. Use boundingRect(const QString &) or width() instead.

    \sa width()
*/
QRect QFontMetrics::boundingRect(QChar ch) const
{
    const int script = QUnicodeTables::script(ch);
    QFontEngine *engine = d->engineForScript(script);
    Q_ASSERT(engine != 0);

    QGlyphLayout glyphs[10];
    int nglyphs = 9;
    engine->stringToCMap(&ch, 1, glyphs, &nglyphs, 0);
    glyph_metrics_t gm = engine->boundingBox(glyphs[0].glyph);
    return QRect(qRound(gm.x), qRound(gm.y), qRound(gm.width), qRound(gm.height));
}

/*!
    \overload

    Returns the bounding rectangle of the characters in the string
    specified by \a str, which is the set of pixels the text would
    cover if drawn at (0, 0). The drawing, and hence the bounding
    rectangle, is constrained to the rectangle \a r.

    The \a flgs argument is the bitwise OR of the following flags:
    \list
    \i Qt::AlignLeft aligns to the left border, except for
          Arabic and Hebrew where it aligns to the right.
    \i Qt::AlignRight aligns to the right border, except for
          Arabic and Hebrew where it aligns to the left.
    \i Qt::AlignJustify produces justified text.
    \i Qt::AlignHCenter aligns horizontally centered.
    \i Qt::AlignTop aligns to the top border.
    \i Qt::AlignBottom aligns to the bottom border.
    \i Qt::AlignVCenter aligns vertically centered
    \i Qt::AlignCenter (== \c{Qt::AlignHCenter | Qt::AlignVCenter})
    \i Qt::TextSingleLine ignores newline characters in the text.
    \i Qt::TextExpandTabs expands tabs (see below)
    \i Qt::TextShowMnemonic interprets "&amp;x" as \underline{x}, i.e. underlined.
    \i Qt::TextWordBreak breaks the text to fit the rectangle.
    \endlist

    Qt::Horizontal alignment defaults to Qt::AlignLeft and vertical
    alignment defaults to Qt::AlignTop.

    If several of the horizontal or several of the vertical alignment
    flags are set, the resulting alignment is undefined.

    These flags are defined in \c qnamespace.h.

    If Qt::TextExpandTabs is set in \a flgs, then: if \a tabarray is
    non-null, it specifies a 0-terminated sequence of pixel-positions
    for tabs; otherwise if \a tabstops is non-zero, it is used as the
    tab spacing (in pixels).

    Note that the bounding rectangle may extend to the left of (0, 0),
    e.g. for italicized fonts, and that the text output may cover \e
    all pixels in the bounding rectangle.

    Newline characters are processed as linebreaks.

    Despite the different actual character heights, the heights of the
    bounding rectangles of "Yes" and "yes" are the same.

    The bounding rectangle returned by this function is somewhat larger
    than that calculated by the simpler boundingRect() function. This
    function uses the \link minLeftBearing() maximum left \endlink and
    \link minRightBearing() right \endlink font bearings as is
    necessary for multi-line text to align correctly. Also,
    fontHeight() and lineSpacing() are used to calculate the height,
    rather than individual character heights.

    \sa width(), QPainter::boundingRect(), Qt::Alignment
*/
QRect QFontMetrics::boundingRect(const QRect &r, int flgs, const QString& str, int tabstops, int *tabarray) const
{
    int tabarraylen=0;
    if (tabarray)
        while (tabarray[tabarraylen])
            tabarraylen++;

    QRectF rb;
    QRectF rr(r);
    qt_format_text(QFont(d), rr, flgs|Qt::TextDontPrint, str, &rb, tabstops, tabarray, tabarraylen, 0);

    return rb.toRect();
}

/*!
    Returns the size in pixels of \a text.

    The \a flgs argument is the bitwise OR of the following flags:
    \list
    \i Qt::TextSingleLine ignores newline characters.
    \i Qt::TextExpandTabs expands tabs (see below)
    \i Qt::TextShowMnemonic interprets "&amp;x" as \underline{x}, i.e. underlined.
    \i Qt::TextWordBreak breaks the text to fit the rectangle.
    \endlist

    These flags are defined in \c qnamespace.h.

    If Qt::TextExpandTabs is set in \a flgs, then: if \a tabarray is
    non-null, it specifies a 0-terminated sequence of pixel-positions
    for tabs; otherwise if \a tabstops is non-zero, it is used as the
    tab spacing (in pixels).

    Newline characters are processed as linebreaks.

    Despite the different actual character heights, the heights of the
    bounding rectangles of "Yes" and "yes" are the same.

    \sa boundingRect()
*/
QSize QFontMetrics::size(int flgs, const QString &text, int tabstops, int *tabarray) const
{
    return boundingRect(QRect(0,0,0,0), flgs, text, tabstops, tabarray).size();
}

/*!
    Returns the distance from the base line to where an underscore
    should be drawn.

    \sa overlinePos(), strikeOutPos(), lineWidth()
*/
int QFontMetrics::underlinePos() const
{
    QFontEngine *engine = d->engineForScript(QUnicodeTables::Common);
    Q_ASSERT(engine != 0);

    return qRound(engine->underlinePosition());
}

/*!
    Returns the distance from the base line to where an overline
    should be drawn.