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QFont Class Reference


The QFont class specifies a font used for drawing text. More...

#include <qfont.h>

List of all member functions.

Public Members

Static Public Members

Protected Members

Related Functions

(Note that these are not member functions.)

Detailed Description

The QFont class specifies a font used for drawing text.

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 application's 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 (also known as fixed-width) 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 setRawName() 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 using 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, QApplication::setFont() 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 for the current locale. \endlink 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 and for more general information on encodings, see or Roman Czyborra's font encodings.

See also: QFontMetrics, QFontInfo, QApplication::setFont(), QWidget::setFont(), QPainter::setFont(), QFont::StyleHint, QFont::CharSet and QFont::Weight.

Examples: showimg/main.cpp grapher/grapher.cpp xform/xform.cpp drawdemo/drawdemo.cpp desktop/desktop.cpp scrollview/scrollview.cpp movies/main.cpp picture/picture.cpp hello/main.cpp


Member Type Documentation

QFont::CharSet

The following character set encodings are available:

QFont::StyleHint

Style hints are 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 value of AnyStyle leaves the task of finding a good default family to the font matching algorithm.

The other available style hints are QFont::SansSerif, QFont::TypeWriter, QFont::OldEnglish, QFont::System

QFont::Weight

Contains the predefined font weights:

Member Function Documentation

QFont::QFont()

Constructs a font object that refers to the default font.

See also: QApplication::setFont() and QApplication::font().

QFont::QFont(constQString&family, intpointSize=12, intweight=Normal, boolitalic=FALSE)

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().

QFont::QFont(constQString&family, intpointSize, intweight, boolitalic, CharSetcharSet)

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().

QFont::QFont(constQFont&font)

Constructs a font that is a copy of font.

QFont::~QFont()

Destroys the font object.

boolQFont::bold()const

Returns TRUE if weight() is a value greater than QFont::Normal, otherwise FALSE.

See also: weight(), setBold() and QFontInfo::bold().

voidQFont::cacheStatistics() [static]

Internal function that dumps font cache statistics.

QFont::CharSetQFont::charSet()const

Returns the character set by setCharSet().

Use QFontInfo to find the CharSet of the window system font actually used.

See also: setCharSet().

voidQFont::cleanup() [static]

Internal function that cleans up the font system.

intQFont::deciPointSize()const [protected]

Returns the point size in 1/10ths of a point.

See also: pointSize().

QStringQFont::defaultFamily()const [protected]

Returns the family name that corresponds to the current style hint.

constQFontQFont::defaultFont() [static]

Returns the QApplication default font.

This function will be removed in a future version of Qt. Please use QApplication::font() instead.

boolQFont::dirty()const [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.

QStringQFont::encodingName(CharSetcs) [static]

Returns the encoding name of a character set, e.g. QFont::ISO_8859_1 returns "iso8859-1" and QFont::Unicode returns "iso10646".

boolQFont::exactMatch()const

Returns TRUE if a window system font exactly matching the settings of this font is available.

See also: QFontInfo and font matching

QStringQFont::family()const

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 );
    qDebug( "Font family requested is    : \"%s\"", font.family() );
    qDebug( "Font family actually used is: \"%s\"", info.family() );

See also: setFamily() and substitute().

boolQFont::fixedPitch()const

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().

voidQFont::initialize() [static]

Internal function that initializes the font system.

voidQFont::insertSubstitution(constQString&familyName, constQString&replacementName) [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().

boolQFont::isCopyOf(constQFont&f)const

Returns TRUE if this font and f are copies of each other, i.e. 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==.

boolQFont::italic()const

Returns the value set by setItalic().

Use QFontInfo to find the italic value of the window system font actually used.

See also: setItalic().

QStringQFont::key()const

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.

See also: QMap.

QStringQFont::lastResortFamily()const [protected]

Returns a last resort family name for the font matching algorithm.

See also: lastResortFont().

QStringQFont::lastResortFont()const [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().

voidQFont::locale_init() [static]

Internal function that uses locale information to find the preferred character set of loaded fonts.

boolQFont::operator!=(constQFont&f)const

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 rawMode() is enabled for both fonts, then only the family fields are compared.

See also: operator==().

QFont&QFont::operator=(constQFont&font)

Assigns font to this font and returns a reference to this font.

boolQFont::operator==(constQFont&f)const

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 rawMode() is enabled for both fonts, then only the family fields are compared.

See also: operator!=().

intQFont::pixelSize()const

Returns the logical pixel height of characters in the font if shown on the screen.

intQFont::pointSize()const

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 );
    qDebug( "Font size requested is    : %d", font.pointSize() );
    qDebug( "Font size actually used is: %d", info.pointSize() );

See also: setPointSize() and deciPointSize().

floatQFont::pointSizeFloat()const

Returns the height of characters in the font in points (1/72 inch).

See also: pointSize().

boolQFont::rawMode()const

Returns the value set by setRawMode().

See also: setRawMode().

QStringQFont::rawName()const

Returns the name of the font within the underlying window system. On Windows, this is usually just the family name of a true type font. Under X, it is a rather complex XLFD (X Logical Font Description). Using the return value of this function is usually not portable.

See also: setRawName().

voidQFont::removeSubstitution(constQString&familyName) [static]

Removes a font family name substitution from the family substitution table.

See also: insertSubstitution(), listSubstitutions() and substitute().

voidQFont::setBold(boolenable)

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().

voidQFont::setCharSet(CharSetcharset)

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
        qFatal( "Cannot find a Latin 1 Times font" );

See also: charSet(), QFontInfo and font matching

voidQFont::setDefaultFont(constQFont&f) [static]

This function is obsolete. It is provided to keep old programs working. We strongly advise against using it in new code.

Sets the QApplication default font.

This function will be removed in a future version of Qt. Please use QApplication::setFont() instead.

voidQFont::setFamily(constQString&family)

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

voidQFont::setFixedPitch(boolenable)

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

voidQFont::setItalic(boolenable)

Sets italic on or off.

See also: italic(), QFontInfo and font matching

voidQFont::setPixelSize(intpixelSize)

Sets the logical height of characters in the font if shown on the screen.

voidQFont::setPixelSizeFloat(floatpixelSize)

Sets the logical pixel height of characters in the font if shown on the screen.

voidQFont::setPointSize(intpointSize)

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

voidQFont::setPointSizeFloat(floatpointSize)

Sets the point size to pointSize. The point size must be greater than zero. The requested precision may not be achieved on all platforms.

voidQFont::setRawName(constQString&name)

Sets a font by its system specific name. The function is in particular useful under X, where system font settings ( for example X resources) are usually available as XLFD (X Logical Font Description) only. You can pass an XLFD as name to this function.

The big advantage over Qt-1.x' concept of raw fonts is, that a font after setRawName() is still a full-featured QFont. It can be queried (for example with italic()) or modified (for example with setItalic() ) and is therefore also suitable as a basis font for rendering rich text.

If Qt's internal font database cannot resolve the raw name, the font becomes a raw font with name as family.

See also: rawName(), setRawMode() and setFamily().

Bugs and limitations:

voidQFont::setStrikeOut(boolenable)

Sets strike out on or off.

See also: strikeOut(), QFontInfo and font matching

voidQFont::setStyleHint(StyleHinthint)

Sets the style hint.

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 the example below 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 );        // preferred family is Bavaria
        font.setStyleHint( QFont::Serif );  // can also use any serif font

        push.setFont( font );
        return app.exec( &push );
    }

See also: QFont::StyleHint, styleHint(), QFontInfo and font matching

Examples: desktop/desktop.cpp

voidQFont::setUnderline(boolenable)

Sets underline on or off.

See also: underline(), QFontInfo and font matching.

voidQFont::setWeight(intweight)

Sets the weight (or boldness), which should be a value from the QFont::Weight enumeration.

Example:

    QFont font( "courier" );
    font.setWeight( QFont::Bold );

Strictly speaking you can use all values in the range [0,99] (where 0 is ultralight and 99 is extremely black), but there is perhaps asking too much of the underlying window system.

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

boolQFont::strikeOut()const

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().

QFont::StyleHintQFont::styleHint()const

Returns the StyleHint set by setStyleHint().

See also: setStyleHint() and QFontInfo::styleHint().

QStringQFont::substitute(constQString&familyName) [static]

Returns the font family name to be used whenever familyName is specified. 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().

QStringListQFont::substitutions() [static]

Returns a sorted list of substituted family names.

See also: insertSubstitution(), removeSubstitution() and substitute().

boolQFont::underline()const

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().

intQFont::weight()const

Returns the weight set by setWeight().

Use QFontInfo to find the weight of the window system font actually used.

See also: setWeight() and QFontInfo.


Related Functions

QDataStream & operator<< (QDataStream & s, const QFont & f)

Writes a font to the stream.

QDataStream & operator>> (QDataStream & s, QFont & f)

Reads a font from the stream.


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