The QFont class specifies a font used for drawing text. More...
#include <qfont.h>
QFont, more precisely, is a collection of attributes of a font. When Qt needs to draw text, it will look up and load the closest matching installed font and draw using that.
The most important attributes of a QFont are family, point size, weight and italic. There are QFont constructors that take these attributes as arguments, as shown in this example:
void MyWidget::paintEvent( QPaintEvent * )
{
QPainter p( this );
// times, 12pt, normal
p.setFont( QFont( "times" ) );
p.drawText( 10, 20, "Text1" );
// helvetica, 18pt, normal
p.setFont( QFont( "helvetica", 18 ) );
p.drawText( 10, 120, "Text2" );
// courier, 24pt, bold
p.setFont( QFont( "courier", 24, QFont::Bold ) );
p.drawText( 10, 220, "Text3" );
// lucida, 36pt, bold, italic
p.setFont( QFont( "lucida", 36, QFont::Bold, TRUE ) );
p.drawText( 10, 320, "Text4" );
}
The default QFont constructor makes a copy of the default font.
You can also change these attributes of an existing QFont object using functions such as setFamily(), setPointSize(), setWeight() and setItalic().
There are also some less-used attributes. setUnderline() decides whether the font is underlined or not; setStrikeOut() can be used to get overstrike (a horizontal line through the middle of the characters); setFixedPitch() determines whether Qt should give preference to fixed-pitch or variable-pitch fonts when it needs to choose an installed font; setStyleHint() can be used to offer more general help to the font matching algorithm, and on X11 setRawMode() can be used to bypass the entire font matching and use an X11 XLFD.
Of course there is also a reader function for each of these set*() functions. Note that the reader functions return the values previously set, not the attributes of the actual window system font that will be used for drawing. You can get information about the font that will be used for drawing by using QFontInfo, but be aware that QFontInfo may be slow and that its results depend on what fonts are installed.
In general font handling and loading are costly operations, especially on X11. The QFont class contains extensive optimizations to make copying of QFont objects fast, and to cache the results of the slow window system functions it uses.
QFont also offers a few static functions, mostly to tune the font matching algorithm: You can control what happens if a font's family isn't installed using insertSubstitution() and removeSubstitution(), ask what happens for a single family uing substitute() and you can get a complete list of the fallback families using listSubstitutions().
cacheStatistics() offers cache effectiveness information; this is useful mostly for debugging.
Finally, setDefaultFont() allows you to set the default font. The default default font is chosen at application startup from a set of common installed fonts that support the correct character set. Of course, the initialization algorithm has a default, too: The default default default font!
For more general information on fonts, see the comp.fonts FAQ.
See also: QFontMetrics, QFontInfo, QApplication::setFont(), QWidget::setFont(), QPainter::setFont(), QFont::StyleHint, QFont::CharSet and QFont::Weight.
Examples: grapher/grapher.cpp desktop/desktop.cpp drawdemo/drawdemo.cpp movies/main.cpp picture/picture.cpp xform/xform.cpp widgets/widgets.cpp
Constructs a font object that refers to the default font.
Constructs a font that is a copy of font.
Constructs a font object with the specified family, pointSize, weight and italic settings. The character set is copied from the default font and the rest of the settings ser set reasonably.
If pointSize is less than or equal to 0 it is set to 1.
See also: setFamily(), setPointSize(), setWeight() and setItalic().
Constructs a font object with the specified family, pointSize, weight, italic and charSet settings. If pointSize is less than or equal to 0 it is set to 1.
See also: setFamily(), setPointSize(), setWeight() and setItalic().
[virtual]Destroys the font object.
Returns TRUE if weight() is a value greater than QFont::Normal,
otherwise FALSE.
See also: weight(), setBold() and QFontInfo::bold().
[static]Internal function that dumps font cache statistics.
Returns the character set by setCharSet().
Use QFontInfo to find the CharSet of the window system font actually used.
See also: setCharSet().
[static]Internal function that cleans up the font system.
[protected]Returns the point size in 1/10ths of a point.
See also: pointSize().
[protected]Returns the family name that corresponds to the current style hint.
[static]Returns the system default font.
[protected]Returns TRUE if the font attributes have been changed and the font has to be (re)loaded, or FALSE if no changes have been made.
Returns TRUE if a window system font exactly matching the settings of this font is available.
See also: QFontInfo and font matching
Returns the family name set by setFamily().
Use QFontInfo to find the family name of the window system font that is actually used for drawing.
Example:
QFont font( "Nairobi" );
QFontInfo info( font );
debug( "Font family requested is : \"%s\"", font.family() );
debug( "Font family actually used is: \"%s\"", info.family() );
See also: setFamily() and substitute().
Returns the value set by setFixedPitch().
Use QFontInfo to find the fixed pitch value of the window system font actually used.
See also: setFixedPitch() and QFontInfo::fixedPitch().
Returns the window system handle to the font, for low-level access. Using this function is not portable.
[static]Internal function that initializes the font system.
[static]Inserts a new font family name substitution in the family substitution table.
If familyName already exists in the substitution table, it will be replaced with this new substitution.
See also: removeSubstitution(), listSubstitutions() and substitute().
Returns TRUE if this font and f are copies of each other, ie. one of them was created as a copy of the other and neither was subsequently modified. This is much stricter than equality.
See also: operator= and operator==.
Returns the value set by setItalic().
Use QFontInfo to find the italic value of the window system font actually used.
See also: setItalic().
Returns the font's key, which is a textual representation of the font settings. It is typically used to insert and find fonts in a dictionary or a cache.
[protected]Returns a last resort family name for the font matching algorithm.
See also: lastResortFont().
[protected]Returns a last resort raw font name for the font matching algorithm.
This is used if not even the last resort family is available.
See also: lastResortFamily().
[static]Returns a sorted list of substituted family names in list.
See also: insertSubstitution(), removeSubstitution() and substitute().
Returns TRUE if the this font is different from f, or FALSE if they are equal.
Two QFonts are different if their font attributes are different. If raw mode is enabled for both fonts, then only the family fields are compared.
See also: operator==().
Assigns font to this font and returns a reference to this font.
Returns TRUE if the this font is equal to f, or FALSE if they are different.
Two QFonts are equal if their font attributes are equal. If raw mode is enabled for both fonts, then only the family fields are compared.
See also: operator!=().
Returns the point size set by setPointSize().
Use QFontInfo to find the point size of the window system font actually used.
Example of use:
QFont font( "helvetica" );
QFontInfo info( font );
font.setPointSize( 53 );
debug( "Font size requested is : %d", font.pointSize() );
debug( "Font size actually used is: %d", info.pointSize() );
See also: setPointSize() and deciPointSize().
Examples: drawdemo/drawdemo.cpp xform/xform.cpp
Returns the value set by setRawMode().
See also: setRawMode().
Returns the name of the font within the underlying system. Using the return value of this function is usually not portable.
See also: setRawMode() and rawMode().
[static]Removes a font family name substitution from the family substitution table.
See also: insertSubstitution(), listSubstitutions() and substitute().
Sets the weight to QFont::Bold if enable is TRUE, or to
QFont::Normal if enable is FALSE.
Use setWeight() to set the weight to other values.
See also: bold() and setWeight().
Sets the character set encoding (e.g. Latin1).
If the character set encoding is not available another will be used for drawing. for most non-trivial applications you will probably not want this to happen since it can totally obscure the text shown to the user. This is why the font matching algorithm gives high priority to finding the correct character set.
You can test that the character set is correct using the QFontInfo class.
Example:
QFont font( "times", 14 ); // default character set is Latin1
QFontInfo info( font );
if ( info.charSet() != Latin1 ) // check actual font
fatal( "Cannot find a Latin 1 Times font" );
In Qt 1.40, the following character set encodings are available:
QFont::Latin1 - ISO 8859-1, common in much of Europe
QFont::Latin2 - ISO 8859-2, less common European character set
QFont::Latin3 - ISO 8859-3, less common European character set
QFont::Latin4 - ISO 8859-4, less common European character set
QFont::Latin5 - ISO 8859-5, Cyrillic
QFont::Latin6 - ISO 8859-6, Arabic
QFont::Latin7 - ISO 8859-7, Greek
QFont::Latin8 - ISO 8859-8, Hebrew
QFont::Latin9 - ISO 8859-9, less common European character set
QFont::KOI8R - KOI8-R, Cyrillic, defined in
RFC 1489.
QFont::AnyCharSet - whatever is handiest.
See also: charSet(), QFontInfo and font matching
[static]Sets the system default font.
Sets the family name of the font (e.g. "Helvetica" or "times").
The family name is case insensitive.
If the family is not available a default family is used.
See also: family(), setStyleHint(), QFontInfo and font matching
Examples: xform/xform.cpp
Sets fixed pitch on or off.
A fixed pitch font is a font where all characters have the same width.
See also: fixedPitch(), QFontInfo and font matching
Sets italic on or off.
See also: italic(), QFontInfo and font matching
Examples: xform/xform.cpp
Sets the point size to pointSize. The point size must be greater than zero.
Example:
QFont font( "courier" );
font.setPointSize( 18 );
See also: pointSize(), QFontInfo and font matching
Examples: drawdemo/drawdemo.cpp xform/xform.cpp
Turns raw mode on if enable is TRUE, or turns it off if enable is FALSE.
Calling this function only has effect under X windows. If raw mode is enabled, Qt will search for an X font with a complete font name matching the family name, ignoring all other values set for the QFont. If the font name matches several fonts, Qt will use the first font returned by X. QFontInfo cannot be used to fetch information about a QFont using raw mode (it will return the values set in the QFont for all parameters, including the family name).
Example:
#if defined(_WS_X11_)
QFont font( "-*-fixed-*-*-*-*-*-140-75-75-c-*-iso8859-1" );
font.setRawMode( TRUE );
if ( !font.exactMatch() )
fatal( "Sorry, could not find the X specific font" );
#endif
Warning: Do not use raw mode unless you really need it!
See also: rawMode().
Sets strike out on or off.
See also: strikeOut(), QFontInfo and font matching
Examples: xform/xform.cpp
Sets the style hint.
The style hint is used by the font matching algorithm when a selected font family cannot be found and is used to find an appropriate default family.
The style hint has a default value of AnyStyle which leaves the
task of finding a good default family to the font matching
algorithm.
In this example (which is a complete program) the push button will display its text label with the Bavaria font family if this family is available, if not it will display its text label with another serif font:
#include <qapplication.h>
#include <qpushbutton.h>
#include <qfont.h>
int main( int argc, char **argv )
{
QApplication app( argc, argv );
QPushButton push("Push me");
QFont font( "Bavaria", 18 ); // preferrred family is Bavaria
font.setStyleHint( QFont::Serif ); // can also use any serif font
push.setFont( font );
return app.exec( &push );
}
The other available style hints are QFont::SansSerif, QFont::TypeWriter, QFont::OldEnglish, QFont::System
See also: styleHint(), QFontInfo and font matching
Examples: desktop/desktop.cpp
Sets underline on or off.
See also: underline(), QFontInfo and font matching.
Examples: xform/xform.cpp
Sets the weight (or boldness).
The enum QFont::Weight contains the predefined font weights:
QFont::Light (25)
QFont::Normal (50)
QFont::DemiBold (63)
QFont::Bold (75)
QFont::Black (87)
Strictly speaking you can use all values in the range [0,99] (where 0 is ultralight and 99 is extremely black), but there is such a thing as asking too much of the underlying window system.
Example:
QFont font( "courier" );
font.setWeight( QFont::Bold );
If the specified weight is not available the closest available will be used. Use QFontInfo to check the actual weight.
See also: weight(), QFontInfo and font matching
Examples: xform/xform.cpp
Returns the value set by setStrikeOut().
Use QFontInfo to find the strike out value of the window system font actually used.
See also: setStrikeOut() and QFontInfo::strikeOut().
Returns the StyleHint set by setStyleHint().
See also: setStyleHint() and QFontInfo::styleHint().
[static]Returns the font family name to be used whenever familyName is specified, and not found by the font matching algorithm. The lookup is case insensitive.
If there is no substitution for familyName, then familyName is returned.
Example:
QFont::insertSubstitution( "NewYork", "London" );
QFont::insertSubstitution( "Paris", "Texas" );
QFont::substitute( "NewYork" ); // returns "London"
QFont::substitute( "PARIS" ); // returns "Texas"
QFont::substitute( "Rome" ); // returns "Rome"
QFont::removeSubstitution( "newyork" );
QFont::substitute( "NewYork" ); // returns "NewYork"
See also: setFamily(), insertSubstitution() and removeSubstitution().
Returns the value set by setUnderline().
Use QFontInfo to find the underline value of the window system font actually used for drawing.
See also: setUnderline() and QFontInfo::underline().
Returns the weight set by setWeight().
Use QFontInfo to find the weight of the window system font actually used.
See also: setWeight() and QFontInfo.
Writes a font to the stream.
Reads a font from the stream.
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