Contents

• Public Types
• Public Functions
• Static Public Members
• Related Non-Members
• Detailed Description

Detailed Description

TheQFont class specifies a font used for drawing text.

When you create aQFont 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 aQFontInfo object. If the window system provides an exact matchexactMatch() returns true. UseQFontMetrics to get measurements, e.g. the pixel length of a string usingQFontMetrics::width().

Note that aQApplication instance must exist before aQFont can be used. You can set the application's default font withQApplication::setFont().

If a chosen 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 aQPainter draws a character from a font theQFont 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,QFont::Bold);QFont sansFont("Helvetica [Cronyx]",12);

The attributes set in the constructor can also be set later, e.g.setFamily(),setPointSize(),setPointSizeFloat(),setWeight() andsetItalic(). The remaining attributes must be set after contstruction, e.g.setBold(),setUnderline(),setOverline(),setStrikeOut() andsetFixedPitch().QFontInfo objects should be createdafter the font's attributes have been set. AQFontInfo 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 aQFontInfo object.

If the requested font family is unavailable you can influence thefont matching algorithm by choosing a particularQFont::StyleHint andQFont::StyleStrategy withsetStyleHint(). The default family (corresponding to the current style hint) is returned bydefaultFamily().

The font-matching algorithm has alastResortFamily() andlastResortFont() in cases where a suitable match cannot be found. You can provide substitutions for font family names usinginsertSubstitution() andinsertSubstitutions(). Substitutions can be removed withremoveSubstitution(). Usesubstitute() to retrieve a family's first substitute, or the family name itself if it has no substitutes. Usesubstitutes() to retrieve a list of a family's substitutes (which may be empty).

EveryQFont has akey() 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 useQSettings, writing the font information withtoString() and reading it back withfromString(). 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 withsetPixelSize(); however usingsetPointSize() has a similar effect and provides device independence.

In X11 you can set a font using its system specific name withsetRawName().

Loading fonts can be expensive, especially on X11.QFont contains extensive optimizations to make the copying ofQFont 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, thestyleHint() 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 nostyleHint(), "helvetica" will be searched for.
5. If "helvetica" isn't found Qt will try thelastResortFamily().
6. If thelastResortFamily() isn't found Qt will try thelastResortFont() which will always return a name of some kind.

Note that the actual font matching algorithm varies from platform to platform.

In Windows a request for the "Courier" font is automatically changed to "Courier New", an improved version of Courier that allows for smooth scaling. The older "Courier" bitmap font can be selected by setting thePreferBitmap style strategy (seesetStyleStrategy()).

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

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

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. AQFontInfo object can be used to determine the actual values used for drawing the text.

Examples:

QFont f("Helvetica");

If you had both an Adobe and a Cronyx Helvetica, you might get either.

QFont f("Helvetica [Cronyx]");

You can specify the foundry you want in the family name. The font f in the above example will be set to "Helvetica [Cronyx]".

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

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

To find out font metrics use aQFontMetrics object, e.g.

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

For more general information on fonts, see thecomp.fonts FAQ. Information on encodings can be found fromRoman Czyborra's page.

Member Type Documentation

enum QFont::Capitalization

Rendering option for text this font applies to.

This enum was introduced or modified in Qt 4.4.

enum QFont::HintingPreference

This enum describes the different levels of hinting that can be applied to glyphs to improve legibility on displays where it might be warranted by the density of pixels.

Please note that this enum only describes a preference, as the full range of hinting levels are not supported on all of Qt's supported platforms. The following table details the effect of a given hinting preference on a selected set of target platforms.

Note:Please be aware that altering the hinting preference on Windows is available through the DirectWrite font engine. This is available on Windows Vista after installing the platform update, and on Windows 7. In order to use this extension, configure Qt using -directwrite. The target application will then depend on the availability of DirectWrite on the target system.

This enum was introduced or modified in Qt 4.8.

enum QFont::SpacingType

This enum was introduced or modified in Qt 4.4.

enum QFont::Stretch

Predefined stretch values that follow the CSS naming convention. The higher the value, the more stretched the text is.

See alsosetStretch() andstretch().

enum QFont::Style

This enum describes the different styles of glyphs that are used to display text.

See alsoWeight.

enum QFont::StyleHint

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

enum QFont::StyleStrategy

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

The following strategies are available:

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

enum 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:

Member Function Documentation

QFont::QFont()

Constructs a font object that uses the application's default font.

See alsoQApplication::setFont() andQApplication::font().

QFont::QFont(constQString & family,int pointSize = -1,int weight = -1,bool italic = false)

Constructs a font object with the specifiedfamily,pointSize,weight anditalic settings.

IfpointSize is zero or negative, the point size of the font is set to a system-dependent default value. Generally, this is 12 points, except on Symbian where it is 7 points.

Thefamily name may optionally also include a foundry name, e.g. "Helvetica [Cronyx]". If thefamily 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 thefont matching algorithm.

See alsoWeight,setFamily(),setPointSize(),setWeight(),setItalic(),setStyleHint(), andQApplication::font().

QFont::QFont(constQFont & font,QPaintDevice * pd)

Constructs a font fromfont for use on the paint devicepd.

QFont::QFont(constQFont & font)

Constructs a font that is a copy offont.

QFont::~QFont()

Destroys the font object and frees all allocated resources.

bool QFont::bold() const

Returns true ifweight() is a value greater thanQFont::Normal; otherwise returns false.

See alsoweight(),setBold(), andQFontInfo::bold().

Capitalization QFont::capitalization() const

Returns the current capitalization type of the font.

This function was introduced in Qt 4.4.

See alsosetCapitalization().

QString QFont::defaultFamily() const

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

See alsoStyleHint,styleHint(), andsetStyleHint().

bool QFont::exactMatch() const

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

See alsoQFontInfo.

QString QFont::family() const

Returns the requested font family name, i.e. the name set in the constructor or the last setFont() call.

See alsosetFamily(),substitutes(), andsubstitute().

bool QFont::fixedPitch() const

Returns true if fixed pitch has been set; otherwise returns false.

See alsosetFixedPitch() andQFontInfo::fixedPitch().

FT_Face QFont::freetypeFace() const

Returns the handle to the primaryFreeType face of the font. If font merging is not disabled aQFont can contain several physical fonts.

Returns 0 if the font does not contain aFreeType face.

Note:This function is only available on platforms that provide theFreeType library; i.e., X11 and some Embedded Linux platforms.

bool QFont::fromString(constQString & descrip)

Sets this font to match the descriptiondescrip. The description is a comma-separated list of the font attributes, as returned bytoString().

See alsotoString().

HFONT QFont::handle() const

Returns the window system handle to the font, for low-level access. Using this function isnot portable.

HintingPreference QFont::hintingPreference() const

Returns the currently preferred hinting level for glyphs rendered with this font.

This function was introduced in Qt 4.8.

See alsosetHintingPreference().

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

InsertssubstituteName into the substitution table for the familyfamilyName.

See alsoinsertSubstitutions(),removeSubstitution(),substitutions(),substitute(), andsubstitutes().

[static]void QFont::insertSubstitutions(constQString & familyName, constQStringList & substituteNames)

Inserts the list of familiessubstituteNames into the substitution list forfamilyName.

See alsoinsertSubstitution(),removeSubstitution(),substitutions(), andsubstitute().

bool QFont::isCopyOf(constQFont & f) const

Returns true if this font andf are copies of each other, i.e. one of them was created as a copy of the other and neither has been modified since. This is much stricter than equality.

See alsooperator=() andoperator==().

bool QFont::italic() const

Returns true if thestyle() of the font is notQFont::StyleNormal

See alsosetItalic() andstyle().

bool QFont::kerning() const

Returns true if kerning should be used when drawing text with this font.

See alsosetKerning().

QString QFont::key() const

Returns the font's key, a textual representation of a font. It is typically used as the key for a cache or dictionary of fonts.

See alsoQMap.

QString QFont::lastResortFamily() const

Returns the "last resort" font family name.

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 an empty string is returned.

See alsolastResortFont().

QString QFont::lastResortFont() const

Returns a "last resort" font name for the font matching algorithm. This is used if the last resort family is not available. It will always return a name, if necessary returning something like "fixed" or "system".

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. Pleasereport it as a bug if it does, preferably with a list of the fonts you have installed.

See alsolastResortFamily() andrawName().

qreal QFont::letterSpacing() const

Returns the letter spacing for the font.

This function was introduced in Qt 4.4.

See alsosetLetterSpacing(),letterSpacingType(), andsetWordSpacing().

SpacingType QFont::letterSpacingType() const

Returns the spacing type used for letter spacing.

This function was introduced in Qt 4.4.

See alsoletterSpacing(),setLetterSpacing(), andsetWordSpacing().

quint32 QFont::macFontID() const

Returns an ATSUFontID

bool QFont::overline() const

Returns true if overline has been set; otherwise returns false.

See alsosetOverline().

int QFont::pixelSize() const

Returns the pixel size of the font if it was set withsetPixelSize(). Returns -1 if the size was set withsetPointSize() orsetPointSizeF().

See alsosetPixelSize(),pointSize(),QFontInfo::pointSize(), andQFontInfo::pixelSize().

int QFont::pointSize() const

Returns the point size of the font. Returns -1 if the font size was specified in pixels.

See alsosetPointSize() andpointSizeF().

qreal QFont::pointSizeF() const

Returns the point size of the font. Returns -1 if the font size was specified in pixels.

See alsopointSize(),setPointSizeF(),pixelSize(),QFontInfo::pointSize(), andQFontInfo::pixelSize().

bool QFont::rawMode() const

Returns true if raw mode is used for font name matching; otherwise returns false.

See alsosetRawMode() andrawName().

QString QFont::rawName() const

Returns the name of the font within the underlying window system.

On X11, this function will return an empty string if Qt is built with FontConfig support; otherwise the XLFD (X Logical Font Description) is returned.

Using the return value of this function is usuallynotportable.

See alsosetRawName().

[static]void QFont::removeSubstitution(constQString & familyName)

Removes all the substitutions forfamilyName.

See alsoinsertSubstitutions(),insertSubstitution(),substitutions(), andsubstitute().

QFont QFont::resolve(constQFont & other) const

Returns a newQFont that has attributes copied fromother that have not been previously set on this font.

void QFont::setBold(bool enable)

Ifenable is true sets the font's weight toQFont::Bold; otherwise sets the weight toQFont::Normal.

For finer boldness control usesetWeight().

See alsobold() andsetWeight().

void QFont::setCapitalization(Capitalization caps)

Sets the capitalization of the text in this font tocaps.

A font's capitalization makes the text appear in the selected capitalization mode.

This function was introduced in Qt 4.4.

See alsocapitalization().

void QFont::setFamily(constQString & family)

Sets the family name of the font. The name is case insensitive and may include a foundry name.

Thefamily name may optionally also include a foundry name, e.g. "Helvetica [Cronyx]". If thefamily 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 thefont matching algorithm.

See alsofamily(),setStyleHint(), andQFontInfo.

void QFont::setFixedPitch(bool enable)

Ifenable is true, sets fixed pitch on; otherwise sets fixed pitch off.

See alsofixedPitch() andQFontInfo.

void QFont::setHintingPreference(HintingPreference hintingPreference)

Set the preference for the hinting level of the glyphs tohintingPreference. This is a hint to the underlying font rendering system to use a certain level of hinting, and has varying support across platforms. See the table in the documentation forQFont::HintingPreference for more details.

The default hinting preference isQFont::PreferDefaultHinting.

This function was introduced in Qt 4.8.

See alsohintingPreference().

void QFont::setItalic(bool enable)

Sets thestyle() of the font toQFont::StyleItalic ifenable is true; otherwise the style is set toQFont::StyleNormal.

See alsoitalic() andQFontInfo.

void QFont::setKerning(bool enable)

Enables kerning for this font ifenable is true; otherwise disables it. By default, kerning is enabled.

When kerning is enabled, glyph metrics do not add up anymore, even for Latin text. In other words, the assumption that width('a') + width('b') is equal to width("ab") is not neccesairly true.

See alsokerning() andQFontMetrics.

void QFont::setLetterSpacing(SpacingType type,qreal spacing)

Sets the letter spacing for the font tospacing and the type of spacing totype.

Letter spacing changes the default spacing between individual letters in the font. The spacing between the letters can be made smaller as well as larger.

This function was introduced in Qt 4.4.

See alsoletterSpacing(),letterSpacingType(), andsetWordSpacing().

void QFont::setOverline(bool enable)

Ifenable is true, sets overline on; otherwise sets overline off.

See alsooverline() andQFontInfo.

void QFont::setPixelSize(int pixelSize)

Sets the font size topixelSize pixels.

Using this function makes the font device dependent. UsesetPointSize() orsetPointSizeF() to set the size of the font in a device independent manner.

See alsopixelSize().

void QFont::setPointSize(int pointSize)

Sets the point size topointSize. The point size must be greater than zero.

See alsopointSize() andsetPointSizeF().

void QFont::setPointSizeF(qreal pointSize)

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

See alsopointSizeF(),setPointSize(), andsetPixelSize().

void QFont::setRawMode(bool enable)

Ifenable is true, turns raw mode on; otherwise turns raw mode off. This function only has an effect under X11.

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 theQFont. If the font name matches several fonts, Qt will use the first font returned by X.QFontInfocannot be used to fetch information about aQFont using raw mode (it will return the values set in theQFont 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 alsorawMode() andsetRawName().

void QFont::setRawName(constQString & name)

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

A font set with setRawName() is still a full-featuredQFont. It can be queried (for example withitalic()) or modified (for example withsetItalic()) 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 withname as its family.

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

See alsorawName(),setRawMode(), andsetFamily().

void QFont::setStretch(int factor)

Sets the stretch factor for the font.

The stretch factor changes the width of all characters in the font byfactor percent. For example, settingfactor 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 alsostretch() andQFont::Stretch.

void QFont::setStrikeOut(bool enable)

Ifenable is true, sets strikeout on; otherwise sets strikeout off.

See alsostrikeOut() andQFontInfo.

void QFont::setStyle(Style style)

Sets the style of the font tostyle.

See alsostyle(),italic(), andQFontInfo.

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

Sets the style hint and strategy tohint andstrategy, respectively.

If these aren't set explicitly the style hint will default toAnyStyle and the style strategy toPreferDefault.

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

See alsoStyleHint,styleHint(),StyleStrategy,styleStrategy(), andQFontInfo.

void QFont::setStyleName(constQString & styleName)

Sets the style name of the font to the givenstyleName. When set, other style properties likestyle() andweight() will be ignored for font matching.

This function was introduced in Qt 4.8.

See alsostyleName().

void QFont::setStyleStrategy(StyleStrategy s)

Sets the style strategy for the font tos.

See alsostyleStrategy() andQFont::StyleStrategy.

void QFont::setUnderline(bool enable)

Ifenable is true, sets underline on; otherwise sets underline off.

See alsounderline() andQFontInfo.

void QFont::setWeight(int weight)

Sets the weight the font toweight, which should be a value from theQFont::Weight enumeration.

See alsoweight() andQFontInfo.

void QFont::setWordSpacing(qreal spacing)

Sets the word spacing for the font tospacing.

Word spacing changes the default spacing between individual words. A positive value increases the word spacing by a corresponding amount of pixels, while a negative value decreases the inter-word spacing accordingly.

Word spacing will not apply to writing systems, where indiviaul words are not separated by white space.

This function was introduced in Qt 4.4.

See alsowordSpacing() andsetLetterSpacing().

int QFont::stretch() const

Returns the stretch factor for the font.

See alsosetStretch().

bool QFont::strikeOut() const

Returns true if strikeout has been set; otherwise returns false.

See alsosetStrikeOut().

Style QFont::style() const

Returns the style of the font.

See alsosetStyle().

StyleHint QFont::styleHint() const

Returns theStyleHint.

The style hint affects thefont matching algorithm. SeeQFont::StyleHint for the list of available hints.

See alsosetStyleHint(),QFont::StyleStrategy, andQFontInfo::styleHint().

QString QFont::styleName() const

Returns the requested font style name, it will be used to match the font with irregular styles (that can't be normalized in other style properties). It depends on system font support, thus only works for Mac OS X and X11 so far. On Windows irregular styles will be added as separate font families so there is no need for this.

This function was introduced in Qt 4.8.

See alsosetStyleName(),setFamily(), andsetStyle().

StyleStrategy QFont::styleStrategy() const

Returns theStyleStrategy.

The style strategy affects thefont matching algorithm. SeeQFont::StyleStrategy for the list of available strategies.

See alsosetStyleStrategy(),setStyleHint(), andQFont::StyleHint.

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

Returns the first family name to be used wheneverfamilyName is specified. The lookup is case insensitive.

If there is no substitution forfamilyName,familyName is returned.

To obtain a list of substitutions usesubstitutes().

See alsosetFamily(),insertSubstitutions(),insertSubstitution(), andremoveSubstitution().

[static]QStringList QFont::substitutes(constQString & familyName)

Returns a list of family names to be used wheneverfamilyName is specified. The lookup is case insensitive.

If there is no substitution forfamilyName, an empty list is returned.

See alsosubstitute(),insertSubstitutions(),insertSubstitution(), andremoveSubstitution().

[static]QStringList QFont::substitutions()

Returns a sorted list of substituted family names.

See alsoinsertSubstitution(),removeSubstitution(), andsubstitute().

QString QFont::toString() const

Returns a description of the font. The description is a comma-separated list of the attributes, perfectly suited for use inQSettings.

See alsofromString().

bool QFont::underline() const

Returns true if underline has been set; otherwise returns false.

See alsosetUnderline().

int QFont::weight() const

Returns the weight of the font which is one of the enumerated values fromQFont::Weight.

See alsosetWeight(),Weight, andQFontInfo.

qreal QFont::wordSpacing() const

Returns the word spacing for the font.

This function was introduced in Qt 4.4.

See alsosetWordSpacing() andsetLetterSpacing().

QFont::operator QVariant() const

Returns the font as aQVariant

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

Returns true if this font is different fromf; otherwise returns false.

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

See alsooperator==().

bool QFont::operator<(constQFont & f) const

Provides an arbitrary comparison of this font and fontf. All that is guaranteed is that the operator returns false if both fonts are equal and that (f1 < f2) == !(f2 < f1) if the fonts are not equal.

This function is useful in some circumstances, for example if you want to useQFont objects as keys in aQMap.

See alsooperator==(),operator!=(), andisCopyOf().

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

Assignsfont to this font and returns a reference to it.

QFont & QFont::operator=(QFont && other)

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

Returns true if this font is equal tof; otherwise returns false.

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

See alsooperator!=() andisCopyOf().

Related Non-Members

QDataStream &operator<<(QDataStream & s, constQFont & font)

Writes the fontfont to the data streams. (toString() writes to a text stream.)

See alsoFormat of the QDataStream operators.

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

Reads the fontfont from the data streams. (fromString() reads from a text stream.)

See alsoFormat of the QDataStream operators.