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

Public Methods
	QFontMetrics (const QFont &font)

	QFontMetrics (const QFont &font, QPaintDevice *paintDevice)

	QFontMetrics (const QFontMetrics &other)

	~QFontMetrics ()

int	ascent () const

int	averageCharWidth () const

QRect	boundingRect (const QRect &rect, int flags, const QString &text, int tabStops=0, int *tabArray=nullptr) const

QRect	boundingRect (const QString &text) const

QRect	boundingRect (int x, int y, int width, int height, int flags, const QString &text, int tabStops=0, int *tabArray=nullptr) const

QRect	boundingRect (QChar ch) const

int	descent () const

QString	elidedText (const QString &text, Qt::TextElideMode mode, int width, int flags=0) const

int	height () const

bool	inFont (QChar ch) const

bool	inFontUcs4 (char32_t ch) const

int	leading () const

int	leftBearing (QChar ch) const

int	lineSpacing () const

int	lineWidth () const

int	maxWidth () const

int	minLeftBearing () const

int	minRightBearing () const

bool	operator!= (const QFontMetrics &other) const

QFontMetrics &	operator= (const QFontMetrics &other)

QFontMetrics &	operator= (QFontMetrics &&other)

bool	operator== (const QFontMetrics &other) const

int	overlinePos () const

int	rightBearing (QChar ch) const

QSize	size (int flags, const QString &text, int tabStops=0, int *tabArray=nullptr) const

int	strikeOutPos () const

void	swap (QFontMetrics &other)

QRect	tightBoundingRect (const QString &text) const

int	underlinePos () const

int	width (const QString &text, int len, int flags) const

int	width (const QString &text, int len=-1) const

int	width (QChar ch) const

int	xHeight () const

Friends
class	QFontMetricsF

Detailed Description

The QFontMetrics class provides font metrics information. The functions calculate the size of characters and strings for a given font. There are three ways you can create a QFontMetrics object.

Calling the QFontMetrics constructor with a QFont creates a font metrics object for a screen-compatible font, i.e. the font can not be a printer font. If the font is changed later, the font metrics object is not updated.(Note: If you use a printer font the values returned may be inaccurate. Printer fonts are not always accessible so the nearest screen font is used if a printer font is supplied.)
QWidget::fontMetrics() returns the font metrics for a widget's font. This is equivalent to QFontMetrics(widget->font()). If the widget's font is changed later, the font metrics object is not updated.
QPainter::fontMetrics() returns the font metrics for a painter's current font. If the painter's 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.

Methods

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 methods are all fast.

There are also methods which operate on the set of glyphs in the font: minLeftBearing(), minRightBearing() and maxWidth(). These are by slow and should be avoided 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 methods include width() which returns the width of a string in pixels (or points, for a printer), The method boundingRect() returns a rectangle large enough to contain the rendered string. The size() methods returns the size of the bounding rectangle.

QFont font("times", 24);
QFontMetrics fm(font);
 
int pixelsWide = fm.width("What is the width of this text?");
int pixelsHigh = fm.height();

See also: QFont, QFontInfo, QFontDatabase, QFontComboBox

Constructor & Destructor Documentation

QFontMetrics::QFontMetrics ( const QFont & font )

explicit

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

QFontMetrics::QFontMetrics	(	const QFont &	font,
		QPaintDevice *	paintDevice
	)

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.

QFontMetrics::QFontMetrics ( const QFontMetrics & other )

Copy constructs a new QFontMetrics from other.

QFontMetrics::~QFontMetrics ( )

Destroys the font metrics object and frees all allocated resources.

Method Documentation

int QFontMetrics::ascent ( ) const

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()

int QFontMetrics::averageCharWidth ( ) const

Returns the average width of glyphs in the font.

QRect QFontMetrics::boundingRect	(	const QRect &	rect,
		int	flags,
		const QString &	text,
		int	tabStops = `0`,
		int *	tabArray = `nullptr`
	)		const

Returns the bounding rectangle of the characters in the string specified by text, 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 rect.

The flags argument is the bitwise OR of the following flags. The following values are part of the enum Qt::AlignmentFlag.

Qt::AlignLeft	aligns to the left border, except for Arabic and Hebrew where it aligns to the right
Qt::AlignRight	aligns to the right border, except for Arabic and Hebrew where it aligns to the left
Qt::AlignJustify	produces justified text
Qt::AlignHCenter	aligns horizontally centered
Qt::AlignTop	aligns to the top border
Qt::AlignBottom	aligns to the bottom border
Qt::AlignVCenter	aligns vertically centered
Qt::AlignCenter	same as the combination of `Qt::AlignHCenter \| Qt::AlignVCenter`
Qt::TextSingleLine	ignores newline characters in the text
Qt::TextExpandTabs<td expands tabs (see below)
Qt::TextShowMnemonic	interprets "&x" as x (underlined)
Qt::TextWordWrap	breaks the text to fit the rectangle

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.

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

The bounding rectangle may extend to the left of (0, 0) for italicized fonts, and the text output may cover 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 method 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, height() and lineSpacing() are used to calculate the height, rather than individual character heights.

See also: width(), QPainter::boundingRect(), Qt::Alignment

QRect QFontMetrics::boundingRect ( const QString & text ) const

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). 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 by height().

See also: width(), height(), QPainter::boundingRect(), tightBoundingRect()

QRect QFontMetrics::boundingRect	(	int	x,
		int	y,
		int	width,
		int	height,
		int	flags,
		const QString &	text,
		int	tabStops = `0`,
		int *	tabArray = `nullptr`
	)		const

inline

Returns the bounding rectangle for the given text within the rectangle specified by the x and y coordinates, width, and height.

If Qt::TextExpandTabs is set in flags and tabArray is non-null, it specifies a 0-terminated sequence of pixel-positions for tabs, otherwise if tabStops is non-zero, it is used as the tab spacing (in pixels).

QRect QFontMetrics::boundingRect ( QChar ch ) const

Returns the rectangle that is covered by ink if character ch were to be drawn at the origin of the coordinate system. 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. For a space character the rectangle will usually be empty.

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.

See also: width()

int QFontMetrics::descent ( ) const

Returns the descent of the font.

The descent is the distance from the base line to the lowest point characters extend to. In practice, some font designers break this rule to accommodate an unusual character in an exotic language. It is possible however unlikely this value will be too small.

See also: ascent()

QString QFontMetrics::elidedText	(	const QString &	text,
		Qt::TextElideMode	mode,
		int	width,
		int	flags = `0`
	)		const

If the text is wider than width, this methods will return an elided version of the string with some of the text replaced with "...". Otherwise, the method returns the original string.

The mode parameter specifies whether the text is elided on the left, in the middle, or on the right. The width is specified in pixels, not characters. The flags argument is optional and currently only supports Qt::TextShowMnemonic as value.

The ellipsis will follow the layout direction it will be on the right side of the text for right-to-left layouts, and on the left side for right-to-left layouts. This behavior is independent of the text language.

int QFontMetrics::height ( ) const

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

See also: leading(), lineSpacing()

bool QFontMetrics::inFont ( QChar ch ) const

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

bool QFontMetrics::inFontUcs4 ( char32_t ch ) const

Returns true if the given code point ch is a valid character in the font, otherwise returns false.

int QFontMetrics::leading ( ) const

Returns the leading of the font.

This is the natural inter-line spacing.

See also: height(), lineSpacing()

int QFontMetrics::leftBearing ( QChar ch ) const

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(), width()

int QFontMetrics::lineSpacing ( ) const

Returns the distance from one base line to the next.

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

See also: height(), leading()

int QFontMetrics::lineWidth ( ) const

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

See also: underlinePos(), overlinePos(), strikeOutPos()

int QFontMetrics::maxWidth ( ) const

Returns the width of the widest character in the font.

int QFontMetrics::minLeftBearing ( ) const

Returns the minimum left bearing of the font. This is the smallest leftBearing(char) of all characters in the font. This method can be very slow if the font is large.

See also: minRightBearing(), leftBearing()

int QFontMetrics::minRightBearing ( ) const

Returns the minimum right bearing of the font. This is the smallest rightBearing(char) of all characters in the font. This method can be very slow if the font is large.

See also: minLeftBearing(), rightBearing()

bool QFontMetrics::operator!= ( const QFontMetrics & other ) const

inline

Returns true if other is not equal to this object, otherwise returns false.

Two font metrics are considered equal if they were constructed from the same QFont and the paint devices they were constructed for are considered compatible.

See also: operator==()

QFontMetrics & QFontMetrics::operator= ( const QFontMetrics & other )

Copy assigns from other and returns a reference to this object.

QFontMetrics & QFontMetrics::operator= ( QFontMetrics && other )

inline

Move assigns from other and returns a reference to this object.

bool QFontMetrics::operator== ( const QFontMetrics & other ) const

Returns true if other is equal to this object, otherwise returns false.

Two font metrics are considered equal if they were constructed from the same QFont and the paint devices they were constructed for are considered compatible.

See also: operator!=()

int QFontMetrics::overlinePos ( ) const

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

See also: underlinePos(), strikeOutPos(), lineWidth()

int QFontMetrics::rightBearing ( QChar ch ) const

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.

Refer to width() for a graphical description of this metric.

See also: leftBearing(), minRightBearing(), width()

QSize QFontMetrics::size	(	int	flags,
		const QString &	text,
		int	tabStops = `0`,
		int *	tabArray = `nullptr`
	)		const

Returns the size in pixels of text. The flags argument is the bitwise OR of the following flags.

Qt::TextSingleLine ignores newline characters.
Qt::TextExpandTabs expands tabs (see below)
Qt::TextShowMnemonic interprets "&x" as x (underline)
Qt::TextWordBreak breaks the text to fit the rectangle.

If Qt::TextExpandTabs is set in flags, then if tabArray is non-null, it specifies a 0-terminated sequence of pixel-positions for tabs, otherwise if 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.

See also: boundingRect()

int QFontMetrics::strikeOutPos ( ) const

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

See also: underlinePos(), overlinePos(), lineWidth()

void QFontMetrics::swap ( QFontMetrics & other )

inline

Swaps the font metric other with this font metric. This operation is very fast and never fails.

QRect QFontMetrics::tightBoundingRect ( const QString & text ) const

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). 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.

See also: width(), height(), boundingRect()

int QFontMetrics::underlinePos ( ) const

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

See also: overlinePos(), strikeOutPos(), lineWidth()

int QFontMetrics::width	(	const QString &	text,
		int	len,
		int	flags
	)		const

Returns the width in pixels of the first len characters of the given text. If len is negative (the default), the entire string is used.

The return value will not be equal to boundingRect().width(). The boundingRect() returns a rectangle describing the pixels this string will cover whereas width() returns the distance to where the next string should be drawn.

int QFontMetrics::width	(	const QString &	text,
		int	len = `-1`
	)		const

Returns the width in pixels of the first len characters of text. If the value for len is negative the entire string is used.

The return value is not equal to calling "boundingRect().width()". The boundingRect() is a rectangle describing the pixels this string will cover. In comparison, this method returns the delta between the given text and where the next string should start.

See also: boundingRect()

int QFontMetrics::width ( QChar ch ) const

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

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.

This method 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 can not be taken into account. When implementing an interactive text control, use QTextLayout instead.

See also: boundingRect()

int QFontMetrics::xHeight ( ) const

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

Public Methods

Friends

Detailed Description

Methods

Constructor & Destructor Documentation

Method Documentation