The QFont class specifies a font used for drawing text. More...
#include <QFont>
Note: All functions in this class are reentrant.
enum | Capitalization { MixedCase, AllUppercase, AllLowercase, SmallCaps, Capitalize } |
enum | SpacingType { PercentageSpacing, AbsoluteSpacing } |
enum | Stretch { UltraCondensed, ExtraCondensed, Condensed, SemiCondensed, ..., UltraExpanded } |
enum | Style { StyleNormal, StyleItalic, StyleOblique } |
enum | StyleHint { AnyStyle, SansSerif, Helvetica, Serif, ..., System } |
enum | StyleStrategy { PreferDefault, PreferBitmap, PreferDevice, PreferOutline, ..., ForceIntegerMetrics } |
enum | Weight { Light, Normal, DemiBold, Bold, Black } |
QFont () | |
QFont ( const QString & family, int pointSize = -1, int weight = -1, bool italic = false ) | |
QFont ( const QFont & font, QPaintDevice * pd ) | |
QFont ( const QFont & font ) | |
~QFont () | |
bool | bold () const |
Capitalization | capitalization () const |
QString | defaultFamily () const |
bool | exactMatch () const |
QString | family () const |
bool | fixedPitch () const |
FT_Face | freetypeFace () const |
bool | fromString ( const QString & descrip ) |
HFONT | handle () const |
bool | isCopyOf ( const QFont & f ) const |
bool | italic () const |
bool | kerning () const |
QString | key () const |
QString | lastResortFamily () const |
QString | lastResortFont () const |
qreal | letterSpacing () const |
SpacingType | letterSpacingType () const |
quint32 | macFontID () const |
bool | overline () const |
int | pixelSize () const |
int | pointSize () const |
qreal | pointSizeF () const |
bool | rawMode () const |
QString | rawName () const |
QFont | resolve ( const QFont & other ) const |
void | setBold ( bool enable ) |
void | setCapitalization ( Capitalization caps ) |
void | setFamily ( const QString & family ) |
void | setFixedPitch ( bool enable ) |
void | setItalic ( bool enable ) |
void | setKerning ( bool enable ) |
void | setLetterSpacing ( SpacingType type, qreal spacing ) |
void | setOverline ( bool enable ) |
void | setPixelSize ( int pixelSize ) |
void | setPointSize ( int pointSize ) |
void | setPointSizeF ( qreal pointSize ) |
void | setRawMode ( bool enable ) |
void | setRawName ( const QString & name ) |
void | setStretch ( int factor ) |
void | setStrikeOut ( bool enable ) |
void | setStyle ( Style style ) |
void | setStyleHint ( StyleHint hint, StyleStrategy strategy = PreferDefault ) |
void | setStyleStrategy ( StyleStrategy s ) |
void | setUnderline ( bool enable ) |
void | setWeight ( int weight ) |
void | setWordSpacing ( qreal spacing ) |
int | stretch () const |
bool | strikeOut () const |
Style | style () const |
StyleHint | styleHint () const |
StyleStrategy | styleStrategy () const |
QString | toString () const |
bool | underline () const |
int | weight () const |
qreal | wordSpacing () const |
operator QVariant () const | |
bool | operator!= ( const QFont & f ) const |
bool | operator< ( const QFont & f ) const |
QFont & | operator= ( const QFont & font ) |
bool | operator== ( const QFont & f ) const |
void | insertSubstitution ( const QString & familyName, const QString & substituteName ) |
void | insertSubstitutions ( const QString & familyName, const QStringList & substituteNames ) |
void | removeSubstitution ( const QString & familyName ) |
QString | substitute ( const QString & familyName ) |
QStringList | substitutes ( const QString & familyName ) |
QStringList | substitutions () |
QDataStream & | operator<< ( QDataStream & s, const QFont & font ) |
QDataStream & | operator>> ( QDataStream & s, QFont & font ) |
The QFont class specifies a font used for drawing text.
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().
Note that a QApplication instance must exist before a QFont can be used. You can set the application's default font with QApplication::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 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, QFont::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.
In X11 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:
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 the PreferBitmap style strategy (see setStyleStrategy()).
Once a font is found, the remaining attributes are matched in order of priority:
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");
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 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 textWidthInPixels = fm.width("How many pixels wide is this text?"); int textHeightInPixels = 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 QFontComboBox, QFontMetrics, QFontInfo, QFontDatabase, and Character Map Example.
Rendering option for text this font applies to.
Constant | Value | Description |
---|---|---|
QFont::MixedCase | 0 | This is the normal text rendering option where no capitalization change is applied. |
QFont::AllUppercase | 1 | This alters the text to be rendered in all uppercase type. |
QFont::AllLowercase | 2 | This alters the text to be rendered in all lowercase type. |
QFont::SmallCaps | 3 | This alters the text to be rendered in small-caps type. |
QFont::Capitalize | 4 | This alters the text to be rendered with the first character of each word as an uppercase character. |
This enum was introduced or modified in Qt 4.4.
Constant | Value | Description |
---|---|---|
QFont::PercentageSpacing | 0 | A value of 100 will keep the spacing unchanged; a value of 200 will enlarge the spacing after a character by the width of the character itself. |
QFont::AbsoluteSpacing | 1 | A positive value increases the letter spacing by the corresponding pixels; a negative value decreases the spacing. |
This enum was introduced or modified in Qt 4.4.
Predefined stretch values that follow the CSS naming convention. The higher the value, the more stretched the text is.
Constant | Value | Description |
---|---|---|
QFont::UltraCondensed | 50 | 50 |
QFont::ExtraCondensed | 62 | 62 |
QFont::Condensed | 75 | 75 |
QFont::SemiCondensed | 87 | 87 |
QFont::Unstretched | 100 | 100 |
QFont::SemiExpanded | 112 | 112 |
QFont::Expanded | 125 | 125 |
QFont::ExtraExpanded | 150 | 150 |
QFont::UltraExpanded | 200 | 200 |
See also setStretch() and stretch().
This enum describes the different styles of glyphs that are used to display text.
Constant | Value | Description |
---|---|---|
QFont::StyleNormal | 0 | Normal glyphs used in unstyled text. |
QFont::StyleItalic | 1 | Italic glyphs that are specifically designed for the purpose of representing italicized text. |
QFont::StyleOblique | 2 | Glyphs with an italic appearance that are typically based on the unstyled glyphs, but are not fine-tuned for the purpose of representing italicized text. |
See also Weight.
Style hints are used by the font matching algorithm to find an appropriate default family if a selected font family is not available.
Constant | Value | Description |
---|---|---|
QFont::AnyStyle | ? | leaves the font matching algorithm to choose the family. This is the default. |
QFont::SansSerif | Helvetica | the font matcher prefer sans serif fonts. |
QFont::Helvetica | 0 | is a synonym for SansSerif. |
QFont::Serif | Times | the font matcher prefers serif fonts. |
QFont::Times | ? | is a synonym for Serif. |
QFont::TypeWriter | Courier | the font matcher prefers fixed pitch fonts. |
QFont::Courier | ? | a synonym for TypeWriter. |
QFont::OldEnglish | ? | the font matcher prefers decorative fonts. |
QFont::Decorative | OldEnglish | is a synonym for OldEnglish. |
QFont::Monospace | ? | the font matcher prefers fonts that map to the CSS generic font-family 'monospace'. |
QFont::Fantasy | ? | the font matcher prefers fonts that map to the CSS generic font-family 'fantasy'. |
QFont::Cursive | ? | the font matcher prefers fonts that map to the CSS generic font-family 'cursive'. |
QFont::System | ? | the font matcher prefers system fonts. |
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:
Constant | Value | Description |
---|---|---|
QFont::PreferDefault | 0x0001 | the default style strategy. It does not prefer any type of font. |
QFont::PreferBitmap | 0x0002 | prefers bitmap fonts (as opposed to outline fonts). |
QFont::PreferDevice | 0x0004 | prefers device fonts. |
QFont::PreferOutline | 0x0008 | prefers outline fonts (as opposed to bitmap fonts). |
QFont::ForceOutline | 0x0010 | forces the use of outline fonts. |
QFont::NoAntialias | 0x0100 | don't antialias the fonts. |
QFont::PreferAntialias | 0x0080 | antialias if possible. |
QFont::OpenGLCompatible | 0x0200 | forces the use of OpenGL compatible fonts. |
QFont::NoFontMerging | 0x8000 | If the font selected for a certain writing system does not contain a character requested to draw, then Qt automatically chooses a similar looking font that contains the character. The NoFontMerging flag disables this feature. Please note that enabling this flag will not prevent Qt from automatically picking a suitable font when the selected font does not support the writing system of the text. |
Any of these may be OR-ed with one of these flags:
Constant | Value | Description |
---|---|---|
QFont::PreferMatch | 0x0020 | prefer an exact match. The font matcher will try to use the exact font size that has been specified. |
QFont::PreferQuality | 0x0040 | prefer the best quality font. The font matcher will use the nearest standard point size that the font supports. |
QFont::ForceIntegerMetrics | 0x0400 | forces the use of integer values in font engines that support fractional font metrics. |
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:
Constant | Value | Description |
---|---|---|
QFont::Light | 25 | 25 |
QFont::Normal | 50 | 50 |
QFont::DemiBold | 63 | 63 |
QFont::Bold | 75 | 75 |
QFont::Black | 87 | 87 |
Constructs a font object that uses the application's default font.
See also QApplication::setFont() and QApplication::font().
Constructs a font object with the specified family, pointSize, weight and italic settings.
If pointSize 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.
The family name may optionally also include a foundry name, e.g. "Helvetica [Cronyx]". 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().
Constructs a font from font for use on the paint device pd.
Constructs a font that is a copy of font.
Destroys the font object and frees all allocated resources.
Returns true if weight() is a value greater than QFont::Normal; otherwise returns false.
See also weight(), setBold(), and QFontInfo::bold().
Returns the current capitalization type of the font.
This function was introduced in Qt 4.4.
See also setCapitalization().
Returns the family name that corresponds to the current style hint.
See also StyleHint, styleHint(), and setStyleHint().
Returns true if a window system font exactly matching the settings of this font is available.
See also QFontInfo.
Returns the requested font family name, i.e. the name set in the constructor or the last setFont() call.
See also setFamily(), substitutes(), and substitute().