QFont Class Reference

Detailed Description

When you create a QFont object you specify various attributes that you want the font to have. Qt will use the font with the specified attributes, or if no matching font exists, Qt will use the closest matching installed font. The attributes of the font that is actually used are retrievable from a QFontInfo object. If the window system provides an exact match exactMatch() returns TRUE. Use QFontMetrics to get measurements, e.g. the pixel length of a string using QFontMetrics::width().

Use QApplication::setFont() to set the application's default font.

If a choosen X11 font does not include all the characters that need to be displayed, QFont will try to find the characters in the nearest equivalent fonts. When a QPainter draws a character from a font the QFont will report whether or not it has the character; if it does not, QPainter will draw an unfilled square.

Create QFonts like this:

    QFont serifFont( "Times", 10, Bold );
    QFont sansFont( "Helvetica [Cronyx]", 12 );
    

The attributes set in the constructor can also be set later, e.g. setFamily(), setPointSize(), setPointSizeFloat(), setWeight() and setItalic(). The remaining attributes must be set after contstruction, e.g. setBold(), setUnderline(), setOverline(), setStrikeOut() and setFixedPitch(). QFontInfo objects should be created after the font's attributes have been set. A QFontInfo object will not change, even if you change the font's attributes. The corresponding "get" functions, e.g. family(), pointSize(), etc., return the values that were set, even though the values used may differ. The actual values are available from a QFontInfo object.

If the requested font family is unavailable you can influence the font matching algorithm by choosing a particular QFont::StyleHint and QFont::StyleStrategy with setStyleHint(). The default family (corresponding to the current style hint) is returned by defaultFamily().

The font-matching algorithm has a lastResortFamily() and lastResortFont() in cases where a suitable match cannot be found. You can provide substitutions for font family names using insertSubstitution() and insertSubstitutions(). Substitutions can be removed with removeSubstitution(). Use substitute() to retrieve a family's first substitute, or the family name itself if it has no substitutes. Use substitutes() to retrieve a list of a family's substitutes (which may be empty).

Every QFont has a key() which you can use, for example, as the key in a cache or dictionary. If you want to store a user's font preferences you could use QSettings, writing the font information with toString() and reading it back with fromString(). The operator<<() and operator>>() functions are also available, but they work on a data stream.

It is possible to set the height of characters shown on the screen to a specified number of pixels with setPixelSize(); however using setPointSize() has a similar effect and provides device independence.

Under the X Window System you can set a font using its system specific name with setRawName().

Loading fonts can be expensive, especially on X11. QFont contains extensive optimizations to make the copying of QFont objects fast, and to cache the results of the slow window system functions it depends upon.

The font matching algorithm works as follows:

1. The specified font family is searched for.
2. If not found, the styleHint() is used to select a replacement family.
3. Each replacement font family is searched for.
4. If none of these are found or there was no styleHint(), "helvetica" will be searched for.
5. If "helvetica" isn't found Qt will try the lastResortFamily().
6. If the lastResortFamily() isn't found Qt will try the lastResortFont() which will always return a name of some kind.

Once a font is found, the remaining attributes are matched in order of priority:

1. fixedPitch()
2. pointSize() (see below)
3. weight()
4. italic()

If you have a font which matches on family, even if none of the other attributes match, this font will be chosen in preference to a font which doesn't match on family but which does match on the other attributes. This is because font family is the dominant search criteria.

The point size is defined to match if it is within 20% of the requested point size. When several fonts match and are only distinguished by point size, the font with the closest point size to the one requested will be chosen.

The actual family, font size, weight and other font attributes used for drawing text will depend on what's available for the chosen family under the window system. A QFontInfo object can be used to determine the actual values used for drawing the text.

Examples:

    QFont f("Helvetica");
    

    QFont f1( "Helvetica [Cronyx]" );  // Qt 3.x
    QFont f2( "Cronyx-Helvetica" );    // Qt 2.x compatibility
    

To determine the attributes of the font actually used in the window system, use a QFontInfo object, e.g.

    QFontInfo info( f1 );
    QString family = info.family();
    

To find out font metrics use a QFontMetrics object, e.g.

    QFontMetrics fm( f1 );
    int pixelWidth = fm.width( "How many pixels wide is this text?" );
    int pixelHeight = fm.height();
    

For more general information on fonts, see the comp.fonts FAQ. Information on encodings can be found from Roman Czyborra's page.

See also QFontMetrics, QFontInfo, QFontDatabase, QApplication::setFont(), QWidget::font, QPainter::setFont(), QFont::StyleHint, QFont::Weight, Widget Appearance and Style, Graphics Classes, and Implicitly and Explicitly Shared Classes.

Member Type Documentation

QFont::Script

This enum represents Unicode allocated scripts. For exhaustive coverage see The Unicode Standard Version 3.0. The following scripts are supported:

Modern European alphabetic scripts (left to right):

• QFont::Latin - consists of most alphabets based on the original Latin alphabet.
• QFont::Greek - covers ancient and modern Greek and Coptic.
• QFont::Cyrillic - covers the Slavic and non-Slavic languages using cyrillic alphabets.
• QFont::Armenian - contains the Armenian alphabet used with the Armenian language.
• QFont::Georgian - covers at least the language Georgian.
• QFont::Runic - covers the known constituents of the Runic alphabets used by the early and medieval societies in the Germanic, Scandinavian, and Anglo-Saxon areas.
• QFont::Ogham - is an alphabetical script used to write a very early form of Irish.
• QFont::SpacingModifiers - are small signs indicating modifications to the preceeding letter.
• QFont::CombiningMarks - consist of diacritical marks not specific to a particular alphabet, diacritical marks used in combination with mathematical and technical symbols, and glyph encodings applied to multiple letterforms.

Middle Eastern scripts (right to left):

• QFont::Hebrew - is used for writing Hebrew, Yiddish, and some other languages.
• QFont::Arabic - covers the Arabic language as well as Persian, Urdu, Kurdish and some others.
• QFont::Syriac - is used to write the active liturgical languages and dialects of several Middle Eastern and Southeast Indian communities.
• QFont::Thaana - is used to write the Maledivian Dhivehi language.

South and Southeast Asian scripts (left to right with few historical exceptions):

• QFont::Devanagari - covers classical Sanskrit and modern Hindi as well as several other languages.
• QFont::Bengali - is a relative to Devanagari employed to write the Bengali language used in West Bengal/India and Bangladesh as well as several minority languages.
• QFont::Gurmukhi - is another Devanagari relative used to write Punjabi.
• QFont::Gujarati - is closely related to Devanagari and used to write the Gujarati language of the Gujarat state in India.
• QFont::Oriya - is used to write the Oriya language of Orissa state/India.
• QFont::Tamil - is used to write the Tamil language of Tamil Nadu state/India, Sri Lanka, Singapore and parts of Malaysia as well as some minority languages.
• QFont::Telugu - is used to write the Telugu language of Andhra Pradesh state/India and some minority languages.
• QFont::Kannada - is another South Indian script used to write the Kannada language of Karnataka state/India and some minority languages.
• QFont::Malayalam - is used to write the Malayalam language of Kerala state/India.
• QFont::Sinhala - is used for Sri Lanka's majority language Sinhala and is also employed to write Pali, Sanskrit, and Tamil.
• QFont::Thai - is used to write Thai and other Southeast Asian languages.
• QFont::Lao - is a language and script quite similar to Thai.
• QFont::Tibetan - is the script used to write Tibetan in several countries like Tibet, the bordering Indian regions and Nepal. It is also used in the Buddist philosophy and liturgy of the Mongolian cultural area.
• QFont::Myanmar - is mainly used to write the Burmese language of Myanmar (former Burma).
• QFont::Khmer - is the official language of Kampuchea.

East Asian scripts (traditionally top-down, right to left, modern often horizontal left to right):

• QFont::Han - consists of the CJK (Chinese, Japanese, Korean) idiographic characters.
• QFont::Hiragana - is a cursive syllabary used to indicate phonetics and pronounciation of Japanese words.
• QFont::Katakana - is a non-cursive syllabic script used to write Japanese words with visual emphasis and non-Japanese words in a phonetical manner.
• QFont::Hangul - is a Korean script consisting of alphabetic components.
• QFont::Bopomofo - is a phonetic alphabet for Chinese (mainly Mandarin).
• QFont::Yi - (also called Cuan or Wei) is a syllabary used to write the Yi language of Southwestern China, Myanmar, Laos, and Vietnam.

Additional scripts that do not fit well into the script categories above:

• QFont::Ethiopic - is a syllabary used by several Central East African languages.
• QFont::Cherokee - is a left-to-right syllabic script used to write the Cherokee language.
• QFont::CanadianAboriginal - consists of the syllabics used by some Canadian aboriginal societies.
• QFont::Mongolian - is the traditional (and recently reintroduced) script used to write Mongolian.

Symbols:

• QFont::CurrencySymbols - contains currency symbols not encoded in other scripts.
• QFont::LetterlikeSymbols - consists of symbols derived from ordinary letters of an alphabetical script.
• QFont::NumberForms - are provided for compatibility with other existing character sets.
• QFont::MathematicalOperators - consists of encodings for operators, relations and other symbols like arrows used in a mathematical context.
• QFont::TechnicalSymbols - contains representations for control codes, the space symbol, APL symbols and other symbols mainly used in the context of electronic data processing.
• QFont::GeometricSymbols - covers block elements and geometric shapes.
• QFont::MiscellaneousSymbols - consists of a heterogeneous collection of symbols that do not fit any other Unicode character block, e.g. Dingbats.
• QFont::EnclosedAndSquare - is provided for compatibility with some East Asian standards.
• QFont::Braille - is an international writing system used by blind people. This script encodes the 256 eight-dot patterns with the 64 six-dot patterns as a subset.
• QFont::Tagalog
• QFont::Hanunoo
• QFont::Buhid
• QFont::Tagbanwa
• QFont::KatakanaHalfWidth
• QFont::Limbu - (Unicode 4.0)
• QFont::TaiLe - (Unicode 4.0)
• QFont::Unicode - includes all the above scripts.

QFont::Stretch

Predefined stretch values that follow the CSS naming convention.

• QFont::UltraCondensed - 50
• QFont::ExtraCondensed - 62
• QFont::Condensed - 75
• QFont::SemiCondensed - 87
• QFont::Unstretched - 100
• QFont::SemiExpanded - 112
• QFont::Expanded - 125
• QFont::ExtraExpanded - 150
• QFont::UltraExpanded - 200

See also setStretch() and stretch().

QFont::StyleHint

Style hints are used by the font matching algorithm to find an appropriate default family if a selected font family is not available.

• QFont::AnyStyle - leaves the font matching algorithm to choose the family. This is the default.
• QFont::SansSerif - the font matcher prefer sans serif fonts.
• QFont::Helvetica - is a synonym for SansSerif.
• QFont::Serif - the font matcher prefers serif fonts.
• QFont::Times - is a synonym for Serif.
• QFont::TypeWriter - the font matcher prefers fixed pitch fonts.
• QFont::Courier - a synonym for TypeWriter.
• QFont::OldEnglish - the font matcher prefers decorative fonts.
• QFont::Decorative - is a synonym for OldEnglish.
• QFont::System - the font matcher prefers system fonts.

QFont::StyleStrategy

The style strategy tells the font matching algorithm what type of fonts should be used to find an appropriate default family.

The following strategies are available:

• QFont::PreferDefault - the default style strategy. It does not prefer any type of font.
• QFont::PreferBitmap - prefers bitmap fonts (as opposed to outline fonts).
• QFont::PreferDevice - prefers device fonts.
• QFont::PreferOutline - prefers outline fonts (as opposed to bitmap fonts).
• QFont::ForceOutline - forces the use of outline fonts.
• QFont::NoAntialias - don't antialias the fonts.
• QFont::PreferAntialias - antialias if possible.
• QFont::OpenGLCompatible - forces the use of OpenGL compatible fonts.

Any of these may be OR-ed with one of these flags:

• QFont::PreferMatch - prefer an exact match. The font matcher will try to use the exact font size that has been specified.
• QFont::PreferQuality - prefer the best quality font. The font matcher will use the nearest standard point size that the font supports.

QFont::Weight

Qt uses a weighting scale from 0 to 99 similar to, but not the same as, the scales used in Windows or CSS. A weight of 0 is ultralight, whilst 99 will be an extremely black.

This enum contains the predefined font weights:

• QFont::Light - 25
• QFont::Normal - 50
• QFont::DemiBold - 63
• QFont::Bold - 75
• QFont::Black - 87

Member Function Documentation

QFont::QFont ()

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

QFont::QFont ( const QString & family, int pointSize = 12, int weight = Normal, bool italic = FALSE )

If pointSize is <= 0 it is set to 1.

The family name may optionally also include a foundry name, e.g. "Helvetica [Cronyx]". (The Qt 2.x syntax, i.e. "Cronyx-Helvetica", is also supported.) If the family is available from more than one foundry and the foundry isn't specified, an arbitrary foundry is chosen. If the family isn't available a family will be set using the font matching algorithm.

See also Weight, setFamily(), setPointSize(), setWeight(), setItalic(), setStyleHint(), and QApplication::font().

QFont::QFont ( const QFont & font )

QFont::~QFont ()

bool QFont::bold () const

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

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

Example: chart/optionsform.cpp.

int QFont::deciPointSize () const [protected]

The returned value will be -1 if the font size has been specified in pixels.

See also pointSize() and pointSizeFloat().

QString QFont::defaultFamily () const

See also StyleHint, styleHint(), and setStyleHint().

QFont QFont::defaultFont () [static]

Please use QApplication::font() instead.

bool QFont::dirty () const [protected]

bool QFont::exactMatch () const

See also QFontInfo.

QString QFont::family () const

See also setFamily(), substitutes(), and substitute().

Examples: chart/optionsform.cpp and fonts/simple-qfont-demo/viewer.cpp.

bool QFont::fixedPitch () const

See also setFixedPitch() and QFontInfo::fixedPitch().

bool QFont::fromString ( const QString & descrip )

See also toString() and operator>>().

HFONT QFont::handle () const

void QFont::insertSubstitution ( const QString & familyName, const QString & substituteName ) [static]

See also insertSubstitutions(), removeSubstitution(), substitutions(), substitute(), and substitutes().

Example: fonts/simple-qfont-demo/viewer.cpp.

void QFont::insertSubstitutions ( const QString & familyName, const QStringList & substituteNames ) [static]

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

Example: fonts/simple-qfont-demo/viewer.cpp.

bool QFont::isCopyOf ( const QFont & f ) const

See also operator=() and operator==().

bool QFont::italic () const

See also setItalic().

Example: chart/optionsform.cpp.

QString QFont::key () const

See also QMap.

QString QFont::lastResortFamily () const

The current implementation tries a wide variety of common fonts, returning the first one it finds. Is is possible that no family is found in which case a null string is returned.

See also lastResortFont().

QString QFont::lastResortFont () const

The current implementation tries a wide variety of common fonts, returning the first one it finds. The implementation may change at any time, but this function will always return a string containing something.

It is theoretically possible that there really isn't a lastResortFont() in which case Qt will abort with an error message. We have not been able to identify a case where this happens. Please report it as a bug if it does, preferably with a list of the fonts you have installed.

See also lastResortFamily() and rawName().

bool QFont::operator!= ( const QFont & f ) const

Two QFonts are considered to be different if their font attributes are different. If rawMode() is enabled for both fonts, only the family fields are compared.

See also operator==().

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

bool QFont::operator== ( const QFont & f ) const

Two QFonts are considered equal if their font attributes are equal. If rawMode() is enabled for both fonts, only the family fields are compared.

See also operator!=() and isCopyOf().

bool QFont::overline () const

See also setOverline().

int QFont::pixelSize () const

See also setPixelSize(), pointSize(), QFontInfo::pointSize(), and QFontInfo::pixelSize().

int QFont::pointSize () const

See also setPointSize(), deciPointSize(), and pointSizeFloat().

Examples: chart/optionsform.cpp and fonts/simple-qfont-demo/viewer.cpp.

float QFont::pointSizeFloat () const

See also pointSize(), setPointSizeFloat(), pixelSize(), QFontInfo::pointSize(), and QFontInfo::pixelSize().

void QFont::qwsRenderToDisk ( bool all = TRUE )

If the font is large and you are sure that only a subset of characters will ever be required on the target device, passing FALSE for the all parameter can save a significant amount of disk space.

Note that this function is only applicable on Qt/Embedded.

bool QFont::rawMode () const

See also setRawMode() and rawName().

QString QFont::rawName () const

On Windows, this is usually just the family name of a TrueType font.

On X11, it is an XLFD (X Logical Font Description). When Qt is build with Xft support on X11, the return value can be an Xft pattern or an XLFD.

Using the return value of this function is usually not portable.

See also setRawName().

void QFont::removeSubstitution ( const QString & familyName ) [static]

See also insertSubstitutions(), insertSubstitution(), substitutions(), and substitute().

QFont QFont::resolve ( const QFont & other ) const

void QFont::setBold ( bool enable )

If enable is true sets the font's weight to QFont::Bold; otherwise sets the weight to QFont::Normal.

For finer boldness control use setWeight().

See also bold() and setWeight().

Examples: menu/menu.cpp and themes/metal.cpp.

void QFont::setDefaultFont ( const QFont & f ) [static]

Please use QApplication::setFont() instead.

void QFont::setFamily ( const QString & family )

The family name may optionally also include a foundry name, e.g. "Helvetica [Cronyx]". (The Qt 2.x syntax, i.e. "Cronyx-Helvetica", is also supported.) If the family is available from more than one foundry and the foundry isn't specified, an arbitrary foundry is chosen. If the family isn't available a family will be set using the font matching algorithm.

See also family(), setStyleHint(), and QFontInfo.

void QFont::setFixedPitch ( bool enable )

See also fixedPitch() and QFontInfo.

void QFont::setItalic ( bool enable )

See also italic() and QFontInfo.

Examples: fileiconview/qfileiconview.cpp, fonts/simple-qfont-demo/viewer.cpp, and themes/metal.cpp.

void QFont::setOverline ( bool enable )

See also overline() and QFontInfo.

void QFont::setPixelSize ( int pixelSize )

Using this function makes the font device dependent. Use setPointSize() or setPointSizeFloat() to set the size of the font in a device independent manner.

See also pixelSize().

Example: qwerty/qwerty.cpp.

void QFont::setPixelSizeFloat ( float pixelSize )

Sets the logical pixel height of font characters when shown on the screen to pixelSize.

void QFont::setPointSize ( int pointSize )

See also pointSize() and setPointSizeFloat().

Example: fonts/simple-qfont-demo/viewer.cpp.

void QFont::setPointSizeFloat ( float pointSize )

See also pointSizeFloat(), setPointSize(), and setPixelSize().

void QFont::setRawMode ( bool enable )

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).

Warning: Do not use raw mode unless you really, really need it! In most (if not all) cases, setRawName() is a much better choice.

See also rawMode() and setRawName().

void QFont::setRawName ( const QString & name )

A font set with 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 for rendering rich text.

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

Note that the present implementation does not handle wildcards in XLFDs well, and that font aliases (file fonts.alias in the font directory on X11) are not supported.

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

void QFont::setStretch ( int factor )

The stretch factor changes the width of all characters in the font by factor percent. For example, setting factor to 150 results in all characters in the font being 1.5 times ( ie. 150% ) wider. The default stretch factor is 100. The minimum stretch factor is 1, and the maximum stretch factor is 4000.

The stretch factor is only applied to outline fonts. The stretch factor is ignored for bitmap fonts.

NOTE: QFont cannot stretch XLFD fonts. When loading XLFD fonts on X11, the stretch factor is matched against a predefined set of values for the SETWIDTH_NAME field of the XLFD.

See also stretch() and QFont::StyleStrategy.

void QFont::setStrikeOut ( bool enable )

See also strikeOut() and QFontInfo.

void QFont::setStyleHint ( StyleHint hint, StyleStrategy strategy = PreferDefault )

If these aren't set explicitly the style hint will default to AnyStyle and the style strategy to PreferDefault.

Qt does not support style hints on X11 since this information is not provided by the window system.

See also StyleHint, styleHint(), StyleStrategy, styleStrategy(), and QFontInfo.

Examples: desktop/desktop.cpp and fonts/simple-qfont-demo/viewer.cpp.

void QFont::setStyleStrategy ( StyleStrategy s )

See also QFont::StyleStrategy.

void QFont::setUnderline ( bool enable )

See also underline() and QFontInfo.

Examples: fonts/simple-qfont-demo/viewer.cpp and menu/menu.cpp.

void QFont::setWeight ( int weight )

See also weight() and QFontInfo.

Example: fonts/simple-qfont-demo/viewer.cpp.

int QFont::stretch () const

See also setStretch().

bool QFont::strikeOut () const

See also setStrikeOut().

StyleHint QFont::styleHint () const

The style hint affects the font matching algorithm. See QFont::StyleHint for the list of strategies.

See also setStyleHint(), QFont::StyleStrategy, and QFontInfo::styleHint().

StyleStrategy QFont::styleStrategy () const

The style strategy affects the font matching algorithm. See QFont::StyleStrategy for the list of strategies.

See also setStyleHint() and QFont::StyleHint.

QString QFont::substitute ( const QString & familyName ) [static]

If there is no substitution for familyName, familyName is returned.

To obtain a list of substitutions use substitutes().

See also setFamily(), insertSubstitutions(), insertSubstitution(), and removeSubstitution().

QStringList QFont::substitutes ( const QString & familyName ) [static]

If there is no substitution for familyName, an empty list is returned.

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

Example: fonts/simple-qfont-demo/viewer.cpp.

QStringList QFont::substitutions () [static]

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

QString QFont::toString () const

See also fromString() and operator<<().

bool QFont::underline () const

See also setUnderline().

int QFont::weight () const

See also setWeight(), Weight, and QFontInfo.

Related Functions

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

Writes the font font to the data stream s. (toString() writes to a text stream.)

See also Format of the QDataStream operators.

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

Reads the font font from the data stream s. (fromString() reads from a text stream.)

See also Format of the QDataStream operators.

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