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QFontMetricsF Class Reference
[QtGui module]

The QFontMetricsF class provides font metrics information. More...

Methods

Special Methods


Detailed Description

The QFontMetricsF class provides font metrics information.

QFontMetricsF functions calculate the size of characters and strings for a given font. You can construct a QFontMetricsF object with an existing QFont to obtain metrics for that font. If the font is changed later, the font metrics object is not updated.

Once created, the object provides functions to access the individual metrics of the font, its characters, and for strings rendered in the font.

There are several functions that operate on the font: ascent(), descent(), height(), leading() and lineSpacing() return the basic size properties of the font. The underlinePos(), overlinePos(), strikeOutPos() and lineWidth() functions, return the properties of the line that underlines, overlines or strikes out the characters. These functions are all fast.

There are also some functions that operate on the set of glyphs in the font: minLeftBearing(), minRightBearing() and maxWidth(). These are by necessity slow, and we recommend avoiding them if possible.

For each character, you can get its width(), leftBearing() and rightBearing() and find out whether it is in the font using inFont(). You can also treat the character as a string, and use the string functions on it.

The string functions include width(), to return the width of a string in pixels (or points, for a printer), boundingRect(), to return a rectangle large enough to contain the rendered string, and size(), to return the size of that rectangle.

Example:

 QFont font("times", 24);
 QFontMetricsF fm(font);
 qreal pixelsWide = fm.width("What's the width of this text?");
 qreal pixelsHigh = fm.height();

Method Documentation

QFontMetricsF.__init__ (self, QFont)

Constructs a font metrics object for font.

The font metrics will be compatible with the paintdevice used to create font.

The font metrics object holds the information for the font that is passed in the constructor at the time it is created, and is not updated if the font's attributes are changed later.

Use QFontMetricsF(const QFont &, QPaintDevice *) to get the font metrics that are compatible with a certain paint device.

QFontMetricsF.__init__ (self, QFont, QPaintDevice pd)

Constructs a font metrics object for font and paintdevice.

The font metrics will be compatible with the paintdevice passed. If the paintdevice is 0, the metrics will be screen-compatible, ie. the metrics you get if you use the font for drawing text on a widgets or pixmaps, not on a QPicture or QPrinter.

The font metrics object holds the information for the font that is passed in the constructor at the time it is created, and is not updated if the font's attributes are changed later.

QFontMetricsF.__init__ (self, QFontMetrics)

Constructs a font metrics object with floating point precision from the given fontMetrics object.

This function was introduced in Qt 4.2.

QFontMetricsF.__init__ (self, QFontMetricsF)

Constructs a copy of fm.

float QFontMetricsF.ascent (self)

Returns the ascent of the font.

The ascent of a font is the distance from the baseline to the highest position characters extend to. In practice, some font designers break this rule, e.g. when they put more than one accent on top of a character, or to accommodate an unusual character in an exotic language, so it is possible (though rare) that this value will be too small.

See also descent().

float QFontMetricsF.averageCharWidth (self)

Returns the average width of glyphs in the font.

This function was introduced in Qt 4.2.

QRectF QFontMetricsF.boundingRect (self, QChar)

Returns the bounding rectangle of the characters in the string specified by 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, not as linebreaks.

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

See also width(), height(), and QPainter.boundingRect().

QRectF QFontMetricsF.boundingRect (self, QString string)

Returns the bounding rectangle of the character 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 all pixels in the bounding rectangle.

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

See also width().

QRectF QFontMetricsF.boundingRect (self, QRectF rect, int flags, QString text, int tabStops = 0, list tabArray = 0)

The tabArray argument may also be None.

This is an overloaded function.

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

The flags argument is the bitwise OR of the following flags:

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 Qt.AlignmentFlag.

If Qt.TextExpandTabs is set in flags, the following behavior is used to interpret tab characters in the text:

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 maximum left and right 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.

See also width(), QPainter.boundingRect(), and Qt.Alignment.

QRectF QFontMetricsF.boundingRectChar (self, QChar)

float QFontMetricsF.descent (self)

Returns the descent of the font.

The descent is the distance from the base line to the lowest point characters extend to. (Note that this is different from X, which adds 1 pixel.) In practice, some font designers break this rule, e.g. to accommodate an unusual character in an exotic language, so it is possible (though rare) that this value will be too small.

See also ascent().

QString QFontMetricsF.elidedText (self, QString text, Qt.TextElideMode mode, float width, int flags = 0)

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

The 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 width is specified in pixels, not characters.

The flags argument is optional and currently only supports Qt.TextShowMnemonic as value.

This function was introduced in Qt 4.2.

float QFontMetricsF.height (self)

Returns the height of the font.

This is always equal to ascent()+descent()+1 (the 1 is for the base line).

See also leading() and lineSpacing().

bool QFontMetricsF.inFont (self, QChar)

Returns true if character ch is a valid character in the font; otherwise returns false.

bool QFontMetricsF.inFontUcs4 (self, int character)

Returns true if the character given by ch, encoded in UCS-4/UTF-32, is a valid character in the font; otherwise returns false.

This function was introduced in Qt 4.8.

float QFontMetricsF.leading (self)

Returns the leading of the font.

This is the natural inter-line spacing.

See also height() and lineSpacing().

float QFontMetricsF.leftBearing (self, QChar)

Returns the left bearing of character 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.

See also rightBearing(), minLeftBearing(), and width().

float QFontMetricsF.lineSpacing (self)

Returns the distance from one base line to the next.

This value is always equal to leading()+height().

See also height() and leading().

float QFontMetricsF.lineWidth (self)

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

See also underlinePos(), overlinePos(), and strikeOutPos().

float QFontMetricsF.maxWidth (self)

Returns the width of the widest character in the font.

float QFontMetricsF.minLeftBearing (self)

Returns the minimum left bearing of the font.

This is the smallest leftBearing(char) of all characters in the font.

Note that this function can be very slow if the font is large.

See also minRightBearing() and leftBearing().

float QFontMetricsF.minRightBearing (self)

Returns the minimum right bearing of the font.

This is the smallest rightBearing(char) of all characters in the font.

Note that this function can be very slow if the font is large.

See also minLeftBearing() and rightBearing().

float QFontMetricsF.overlinePos (self)

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

See also underlinePos(), strikeOutPos(), and lineWidth().

float QFontMetricsF.rightBearing (self, QChar)

Returns the right bearing of character 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.

See also leftBearing(), minRightBearing(), and width().

QSizeF QFontMetricsF.size (self, int flags, QString text, int tabStops = 0, list tabArray = 0)

The tabArray argument may also be None.

Returns the size in pixels of the characters in the given text.

The flags argument is the bitwise OR of the following flags:

These flags are defined in Qt.TextFlags.

If Qt.TextExpandTabs is set in flags, the following behavior is used to interpret tab characters in the text:

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.

See also boundingRect().

float QFontMetricsF.strikeOutPos (self)

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

See also underlinePos(), overlinePos(), and lineWidth().

QRectF QFontMetricsF.tightBoundingRect (self, QString text)

Returns a tight bounding rectangle around the characters in the string specified by 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, not as linebreaks.

Warning: Calling this method is very slow on Windows.

This function was introduced in Qt 4.3.

See also width(), height(), and boundingRect().

float QFontMetricsF.underlinePos (self)

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

See also overlinePos(), strikeOutPos(), and lineWidth().

float QFontMetricsF.width (self, QChar)

Returns the width in pixels of the characters in the given text.

Note that this value is 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.

See also boundingRect().

float QFontMetricsF.width (self, QString string)

This is an overloaded function.

Bearings

Returns the logical width of character ch in pixels. This is a distance appropriate for drawing a subsequent character after 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. When implementing an interactive text control, use QTextLayout instead.

See also boundingRect().

float QFontMetricsF.widthChar (self, QChar)

float QFontMetricsF.xHeight (self)

Returns the 'x' height of the font. This is often but not always the same as the height of the character 'x'.

bool QFontMetricsF.__eq__ (self, QFontMetricsF other)

bool QFontMetricsF.__ne__ (self, QFontMetricsF other)


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