qfontmetrics.cpp

奇趣公司比较新的qt/emd版本

    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 gi.x.toReal();
}

/*!
    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()
*/
qreal QFontMetricsF::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 (gi.xoff - gi.x - gi.width).toReal();
}

/*!
    Returns the width in pixels of the characters in the given \a text.

    Note that this value is \e not equal to the width returned by
    boundingRect().width() because 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()
*/
qreal QFontMetricsF::width(const QString &text) const
{
    QTextEngine layout(text, d);
    layout.ignoreBidi = true;
    layout.itemize();
    return layout.width(0, text.length()).toReal();
}

/*!
    \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()
*/
qreal QFontMetricsF::width(QChar ch) const
{
    if (QChar::category(ch.unicode()) == 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 glyphs[0].advance.x.toReal();
}

/*!
    Returns the bounding rectangle of the characters in the string
    specified by \a text. The bounding rectangle always covers at least
    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 width of the returned
    rectangle might be different than what the width() method returns.

    If you want to know the advance width of the string (to layout
    a set of strings next to each other), use width() instead.

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

    The height of the bounding rectangle is at least as large as the
    value returned height().

    \sa width(), height(), QPainter::boundingRect()
*/
QRectF QFontMetricsF::boundingRect(const QString &text) const
{
    int len = text.length();
    if (len == 0)
        return QRectF();

    QTextEngine layout(text, d);
    layout.ignoreBidi = true;
    layout.itemize();
    glyph_metrics_t gm = layout.boundingBox(0, len);
    return QRectF(gm.x.toReal(), gm.y.toReal(),
                  gm.width.toReal(), gm.height.toReal());
}

/*!
    Returns the bounding rectangle of the character \a ch relative to
    the left-most point on the base line.

    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.

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

    \sa width()
*/
QRectF QFontMetricsF::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 QRectF(gm.x.toReal(), gm.y.toReal(), gm.width.toReal(), gm.height.toReal());
}

/*!
    \overload

    Returns the bounding rectangle of the characters in the given \a text.
    This is the set of pixels the text would cover if drawn when constrained
    to the bounding rectangle specified by \a rect.

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

    If Qt::TextExpandTabs is set in \a flags, the following behavior is
    used to interpret tab characters in the text:
    \list
    \o If \a tabArray is non-null, it specifies a 0-terminated sequence of
       pixel-positions for tabs in the text.
    \o If \a tabStops is non-zero, it is used as the tab spacing (in pixels).
    \endlist

    Note that the bounding rectangle may extend to the left of (0, 0),
    e.g. for italicized fonts.

    Newline characters are processed as line breaks.

    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
*/
QRectF QFontMetricsF::boundingRect(const QRectF &rect, int flags, const QString& text,
                                   int tabStops, int *tabArray) const
{
    int tabArrayLen = 0;
    if (tabArray)
        while (tabArray[tabArrayLen])
            tabArrayLen++;

    QRectF rb;
    qt_format_text(QFont(d), rect, flags | Qt::TextDontPrint, text, &rb, tabStops, tabArray,
                   tabArrayLen, 0);
    return rb;
}

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

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

    These flags are defined in \l{Qt::TextFlags}.

    If Qt::TextExpandTabs is set in \a flags, the following behavior is
    used to interpret tab characters in the text:
    \list
    \o If \a tabArray is non-null, it specifies a 0-terminated sequence of
       pixel-positions for tabs in the text.
    \o If \a tabStops is non-zero, it is used as the tab spacing (in pixels).
    \endlist

    Newline characters are processed as line breaks.

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

    \sa boundingRect()
*/
QSizeF QFontMetricsF::size(int flags, const QString &text, int tabStops, int *tabArray) const
{
    return boundingRect(QRectF(), flags, text, tabStops, tabArray).size();
}

/*!
  \since 4.3

    Returns a tight bounding rectangle around the characters in the
    string specified by \a text. The bounding rectangle always covers
    at least 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 width of the returned
    rectangle might be different than what the width() method returns.

    If you want to know the advance width of the string (to layout
    a set of strings next to each other), use width() instead.

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

    \warning Calling this method is very slow on Windows.

    \sa width(), height(), boundingRect()
*/
QRectF QFontMetricsF::tightBoundingRect(const QString &text) const
{
    if (text.length() == 0)
        return QRect();

    QTextEngine layout(text, d);
    layout.ignoreBidi = true;
    layout.itemize();
    glyph_metrics_t gm = layout.tightBoundingBox(0, text.length());
    return QRectF(gm.x.toReal(), gm.y.toReal(), gm.width.toReal(), gm.height.toReal());
}

/*!
    \since 4.2

    If the string \a text is wider than \a width, returns an elided
    version of the string (i.e., a string with "..." in it).
    Otherwise, returns the original string.

    The \a mode parameter specifies whether the text is elided on the
    left (e.g., "...tech"), in the middle (e.g., "Tr...ch"), or on
    the right (e.g., "Trol...").

    The \a width is specified in pixels, not characters.

    The \a flags argument is optional and currently only supports
    Qt::TextShowMnemonic as value.
*/
QString QFontMetricsF::elidedText(const QString &text, Qt::TextElideMode mode, qreal width, int flags) const
{
    QStackTextEngine engine(text, QFont(d));
    return engine.elidedText(mode, QFixed::fromReal(width), flags);
}

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

    \sa overlinePos(), strikeOutPos(), lineWidth()
*/
qreal QFontMetricsF::underlinePos() const
{
    QFontEngine *engine = d->engineForScript(QUnicodeTables::Common);
    Q_ASSERT(engine != 0);
    return engine->underlinePosition().toReal();
}

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

    \sa underlinePos(), strikeOutPos(), lineWidth()
*/
qreal QFontMetricsF::overlinePos() const
{
    return ascent() + 1;
}

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

    \sa underlinePos(), overlinePos(), lineWidth()
*/
qreal QFontMetricsF::strikeOutPos() const
{
    return ascent() / 3.;
}

/*!
    Returns the width of the underline and strikeout lines, adjusted
    for the point size of the font.

    \sa underlinePos(), overlinePos(), strikeOutPos()
*/
qreal QFontMetricsF::lineWidth() const
{
    QFontEngine *engine = d->engineForScript(QUnicodeTables::Common);
    Q_ASSERT(engine != 0);
    return engine->lineThickness().toReal();
}

/*!
    \fn QSize QFontMetrics::size(int flags, const QString &text, int len,
                                 int tabStops, int *tabArray) const
    \compat

    Use the size() function in combination with QString::left()
    instead.

    \oldcode
        QSize size = size(flags, str, len, tabstops, tabarray);
    \newcode
        QSize size = size(flags, str.left(len), tabstops, tabarray);
    \endcode
*/

/*!
    \fn QRect QFontMetrics::boundingRect(int x, int y, int w, int h, int flags,
        const QString& text, int len, int tabStops, int *tabArray) const
    \compat

    Use the boundingRect() function in combination with
    QString::left() and a QRect constructor instead.

    \oldcode
        QRect rect = boundingRect(x, y, w, h , flags, text, len,
                                  tabStops, tabArray);
    \newcode
        QRect rect = boundingRect(QRect(x, y, w, h), flags, text.left(len),
                                  tabstops, tabarray);
    \endcode

*/

/*!
    \fn QRect QFontMetrics::boundingRect(const QString &text, int len) const
    \compat

    Use the boundingRect() function in combination with
    QString::left() instead.

    \oldcode
        QRect rect = boundingRect(text, len);
    \newcode
        QRect rect = boundingRect(text.left(len));
    \endcode
*/