QFontMetrics(3qt)QFontMetrics(3qt)NAMEQFontMetrics - Font metrics information
SYNOPSIS
#include <qfontmetrics.h>
Public Members
QFontMetrics ( const QFont & font )
QFontMetrics ( const QFont & font, QFont::Script script )
QFontMetrics ( const QFontMetrics & fm )
~QFontMetrics ()
QFontMetrics & operator= ( const QFontMetrics & fm )
int ascent () const
int descent () const
int height () const
int leading () const
int lineSpacing () const
int minLeftBearing () const
int minRightBearing () const
int maxWidth () const
bool inFont ( QChar ch ) const
int leftBearing ( QChar ch ) const
int rightBearing ( QChar ch ) const
int width ( const QString & str, int len = -1 ) const
int width ( QChar ch ) const
int width ( char c ) const (obsolete)
int charWidth ( const QString & str, int pos ) const
QRect boundingRect ( const QString & str, int len = -1 ) const
QRect boundingRect ( QChar ch ) const
QRect boundingRect ( int x, int y, int w, int h, int flgs, const
QString & str, int len = -1, int tabstops = 0, int * tabarray = 0,
QTextParag ** intern = 0 ) const
QSize size ( int flgs, const QString & str, int len = -1, int tabstops
= 0, int * tabarray = 0, QTextParag ** intern = 0 ) const
int underlinePos () const
int overlinePos () const
int strikeOutPos () const
int lineWidth () const
DESCRIPTION
The QFontMetrics class provides font metrics information.
QFontMetrics functions calculate the size of characters and strings for
a given font. There are three ways you can create a QFontMetrics
object:
<ol type=1>
1 Calling the QFontMetrics constructor with a QFont creates a font
metrics object for a screen-compatible font, i.e. the font
cannot be a printer font<sup>*</sup>. If the font is changed
later, the font metrics object is not updated.
2 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.
3 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.
<sup>*</sup> 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.
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 );
QFontMetrics fm( font );
int pixelsWide = fm.width( "What's the width of this text?" );
int pixelsHigh = fm.height();
See also QFont, QFontInfo, QFontDatabase, Graphics Classes, and
Implicitly and Explicitly Shared Classes.
MEMBER FUNCTION DOCUMENTATIONQFontMetrics::QFontMetrics ( const QFont & font )
Constructs a font metrics object for font.
The font must be screen-compatible, i.e. a font you use when drawing
text in widgets or pixmaps, not 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.
Use QPainter::fontMetrics() to get the font metrics when painting. This
will give correct results also when painting on paint device that is
not screen-compatible.
QFontMetrics::QFontMetrics ( const QFont & font, QFont::Script script )
This is an overloaded member function, provided for convenience. It
behaves essentially like the above function.
Constructs a font metrics object for font using the given script.
QFontMetrics::QFontMetrics ( const QFontMetrics & fm )
Constructs a copy of fm.
QFontMetrics::~QFontMetrics ()
Destroys the font metrics object and frees all allocated resources.
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().
Examples:
QRect QFontMetrics::boundingRect ( QChar ch ) const
Returns the rectangle that is covered by ink if the character specified
by ch were 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 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.
See also width().
Example: xform/xform.cpp.
QRect QFontMetrics::boundingRect ( const QString & str, int len = -1 ) const
This is an overloaded member function, provided for convenience. It
behaves essentially like the above function.
Returns the bounding rectangle that contains the first len characters
of string str.
QRect QFontMetrics::boundingRect ( int x, int y, int w, int h, int flgs, const
QString & str, int len = -1, int tabstops = 0, int * tabarray = 0,
QTextParag ** intern = 0 ) const
This is an overloaded member function, provided for convenience. It
behaves essentially like the above function.
Returns the bounding rectangle of the first len characters of 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 (x, y, w, h).
If len is negative (which is the default), the entire string is used.
The flgs argument is the bitwise OR of the following flags:
AlignAuto aligns to the left border for all languages except Arabic and
Hebrew where it aligns to the right.
AlignLeft aligns to the left border.
AlignRight aligns to the right border.
AlignJustify produces justified text.
AlignHCenter aligns horizontally centered.
AlignTop aligns to the top border.
AlignBottom aligns to the bottom border.
AlignVCenter aligns vertically centered
AlignCenter (== AlignHCenter | AlignVCenter)
SingleLine ignores newline characters in the text.
ExpandTabs expands tabs (see below)
ShowPrefix interprets "&x" as "<u>x</u>", i.e. underlined.
WordBreak breaks the text to fit the rectangle.
Horizontal alignment defaults to AlignAuto and vertical alignment
defaults to 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 qnamespace.h.
If ExpandTabs is set in flgs, 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).
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.
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 given 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.
The intern argument should not be used.
See also width(), QPainter::boundingRect(), and Qt::AlignmentFlags.
int QFontMetrics::charWidth ( const QString & str, int pos ) const
Returns the width of the character at position pos in the string 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::descent () const
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().
Examples:
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() and lineSpacing().
Examples:
bool QFontMetrics::inFont ( QChar ch ) const
Returns TRUE if character ch is a valid character in the font;
otherwise returns FALSE.
Example: qfd/fontdisplayer.cpp.
int QFontMetrics::leading () const
Returns the leading of the font.
This is the natural inter-line spacing.
See also height() and 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(), and width().
Example: qfd/fontdisplayer.cpp.
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() and leading().
Examples:
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(), and strikeOutPos().
int QFontMetrics::maxWidth () const
Returns the width of the widest character in the font.
Example: qfd/fontdisplayer.cpp.
int QFontMetrics::minLeftBearing () const
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().
Example: qfd/fontdisplayer.cpp.
int QFontMetrics::minRightBearing () const
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().
Example: qfd/fontdisplayer.cpp.
QFontMetrics & QFontMetrics::operator= ( const QFontMetrics & fm )
Assigns the font metrics fm.
int QFontMetrics::overlinePos () const
Returns the distance from the base line to where an overline should be
drawn.
See also underlinePos(), strikeOutPos(), and 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.
See width() for a graphical description of this metric.
See also leftBearing(), minRightBearing(), and width().
Example: qfd/fontdisplayer.cpp.
QSize QFontMetrics::size ( int flgs, const QString & str, int len = -1, int
tabstops = 0, int * tabarray = 0, QTextParag ** intern = 0 ) const
Returns the size in pixels of the first len characters of str.
If len is negative (the default), the entire string is used.
The flgs argument is the bitwise OR of the following flags:
SingleLine ignores newline characters.
ExpandTabs expands tabs (see below)
ShowPrefix interprets "&x" as "<u>x</u>", i.e. underlined.
WordBreak breaks the text to fit the rectangle.
These flags are defined in qnamespace.h.
If ExpandTabs is set in flgs, 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.
The intern argument should not be used.
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(), and lineWidth().
int QFontMetrics::underlinePos () const
Returns the distance from the base line to where an underscore should
be drawn.
See also overlinePos(), strikeOutPos(), and lineWidth().
int QFontMetrics::width ( QChar ch ) const
[Image Omitted]
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. Use charWidth() instead if you aren't
looking for the width of isolated characters.
See also boundingRect() and charWidth().
Examples:
int QFontMetrics::width ( const QString & str, int len = -1 ) const
This is an overloaded member function, provided for convenience. It
behaves essentially like the above function.
Returns the width of the first len characters of string str.
int QFontMetrics::width ( char c ) const
This is an overloaded member function, provided for convenience. It
behaves essentially like the above function.
This function is obsolete. It is provided to keep old source working.
We strongly advise against using it in new code.
Provided to aid porting from Qt 1.x.
SEE ALSO
http://doc.trolltech.com/qfontmetrics.html
http://www.trolltech.com/faq/tech.html
COPYRIGHT
Copyright 1992-2007 Trolltech ASA, http://www.trolltech.com. See the
license file included in the distribution for a complete license
statement.
AUTHOR
Generated automatically from the source code.
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Trolltech AS 2 February 2007 QFontMetrics(3qt)