QFont Class ReferenceThe QFont class specifies a font used for drawing text. Далее... #include <QFont>Замечание: Все функции в этом классе реентерабельны. Открытые типы
Открытые функции
Статические открытые члены
Связанные нечлены класса
Подробное описаниеThe 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 будет использовать шрифт с заданными атрибутами или, если нет соответствующего шрифта, то Qt будет использовать наиболее похожий установленный шрифт. 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. Примеры: 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. Описание типов-членовenum QFont::CapitalizationRendering option for text this font applies to.
Данное перечисление было введено или модифицировано в Qt 4.4. enum QFont::HintingPreferenceThis 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. Данное перечисление было введено или модифицировано в Qt 4.8. enum QFont::SpacingType
Данное перечисление было введено или модифицировано в Qt 4.4. enum QFont::StretchPredefined stretch values that follow the CSS naming convention. The higher the value, the more stretched the text is.
See also setStretch() and stretch(). enum QFont::StyleThis enum describes the different styles of glyphs that are used to display text.
See also Weight. enum QFont::StyleHintStyle hints are used by the font matching algorithm to find an appropriate default family if a selected font family is not available.
enum QFont::StyleStrategyThe 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:
Any of these may be OR-ed with one of these flags:
enum QFont::WeightQt 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:
Описание функций-членовQFont::QFont ()Constructs a font object that uses the application's default font. See also QApplication::setFont() and QApplication::font(). QFont::QFont ( const QString & family, int pointSize = -1, int weight = -1, bool italic = false )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(). QFont::QFont ( const QFont & font, QPaintDevice * pd )Constructs a font from font for use on the paint device pd. QFont::QFont ( const QFont & font )Constructs a font that is a copy of font. QFont::~QFont ()Destroys the font object and frees all allocated resources. bool QFont::bold () constReturns true if weight() is a value greater than QFont::Normal; otherwise returns false. See also weight(), setBold(), and QFontInfo::bold(). Capitalization QFont::capitalization () constReturns the current capitalization type of the font. Эта функция была введена в Qt 4.4. See also setCapitalization(). QString QFont::defaultFamily () constReturns the family name that corresponds to the current style hint. See also StyleHint, styleHint(), and setStyleHint(). bool QFont::exactMatch () constReturns true if a window system font exactly matching the settings of this font is available. See also QFontInfo. QString QFont::family () constReturns the requested font family name, i.e. the name set in the constructor or the last setFont() call. See also setFamily(), substitutes(), and substitute(). bool QFont::fixedPitch () constReturns true if fixed pitch has been set; otherwise returns false. See also setFixedPitch() and QFontInfo::fixedPitch(). FT_Face QFont::freetypeFace () constReturns the handle to the primary FreeType face of the font. If font merging is not disabled a QFont can contain several physical fonts. Returns 0 if the font does not contain a FreeType face. Note: This function is only available on platforms that provide the FreeType library; i.e., X11 and some Embedded Linux platforms. bool QFont::fromString ( const QString & descrip )Sets this font to match the description descrip. The description is a comma-separated list of the font attributes, as returned by toString(). Смотрите также toString(). HFONT QFont::handle () constReturns the window system handle to the font, for low-level access. Using this function is not portable. HintingPreference QFont::hintingPreference () constReturns the currently preferred hinting level for glyphs rendered with this font. Эта функция была введена в Qt 4.8. See also setHintingPreference(). void QFont::insertSubstitution ( const QString & familyName, const QString & substituteName ) [static]Inserts substituteName into the substitution table for the family familyName. See also insertSubstitutions(), removeSubstitution(), substitutions(), substitute(), and substitutes(). void QFont::insertSubstitutions ( const QString & familyName, const QStringList & substituteNames ) [static]Inserts the list of families substituteNames into the substitution list for familyName. See also insertSubstitution(), removeSubstitution(), substitutions(), and substitute(). bool QFont::isCopyOf ( const QFont & f ) constReturns 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 has been modified since. This is much stricter than equality. See also operator=() and operator==(). bool QFont::italic () constReturns true if the style() of the font is not QFont::StyleNormal See also setItalic() and style(). bool QFont::kerning () constReturns true if kerning should be used when drawing text with this font. See also setKerning(). QString QFont::key () constReturns 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 also QMap. QString QFont::lastResortFamily () constReturns 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 also lastResortFont(). QString QFont::lastResortFont () constReturns 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. Please report it as a bug if it does, preferably with a list of the fonts you have installed. See also lastResortFamily() and rawName(). qreal QFont::letterSpacing () constReturns the letter spacing for the font. Эта функция была введена в Qt 4.4. See also setLetterSpacing(), letterSpacingType(), and setWordSpacing(). SpacingType QFont::letterSpacingType () constReturns the spacing type used for letter spacing. Эта функция была введена в Qt 4.4. See also letterSpacing(), setLetterSpacing(), and setWordSpacing(). quint32 QFont::macFontID () constReturns an ATSUFontID bool QFont::overline () constReturns true if overline has been set; otherwise returns false. See also setOverline(). int QFont::pixelSize () constReturns the pixel size of the font if it was set with setPixelSize(). Returns -1 if the size was set with setPointSize() or setPointSizeF(). See also setPixelSize(), pointSize(), QFontInfo::pointSize(), and QFontInfo::pixelSize(). int QFont::pointSize () constReturns the point size of the font. Returns -1 if the font size was specified in pixels. See also setPointSize() and pointSizeF(). qreal QFont::pointSizeF () constReturns the point size of the font. Returns -1 if the font size was specified in pixels. See also pointSize(), setPointSizeF(), pixelSize(), QFontInfo::pointSize(), and QFontInfo::pixelSize(). bool QFont::rawMode () constReturns true if raw mode is used for font name matching; otherwise returns false. See also setRawMode() and rawName(). QString QFont::rawName () constReturns 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 usually not portable. See also setRawName(). void QFont::removeSubstitution ( const QString & familyName ) [static]Removes all the substitutions for familyName. See also insertSubstitutions(), insertSubstitution(), substitutions(), and substitute(). QFont QFont::resolve ( const QFont & other ) constReturns a new QFont that has attributes copied from other that have not been previously set on this font. 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(). void QFont::setCapitalization ( Capitalization caps )Sets the capitalization of the text in this font to caps. A font's capitalization makes the text appear in the selected capitalization mode. Эта функция была введена в Qt 4.4. See also capitalization(). void QFont::setFamily ( const QString & family )Sets the family name of the font. The name is case insensitive and may include a foundry name. 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 family(), setStyleHint(), and QFontInfo. void QFont::setFixedPitch ( bool enable )If enable is true, sets fixed pitch on; otherwise sets fixed pitch off. See also fixedPitch() and QFontInfo. void QFont::setHintingPreference ( HintingPreference hintingPreference )Set the preference for the hinting level of the glyphs to hintingPreference. 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 for QFont::HintingPreference for more details. The default hinting preference is QFont::PreferDefaultHinting. Эта функция была введена в Qt 4.8. See also hintingPreference(). void QFont::setItalic ( bool enable )Sets the style() of the font to QFont::StyleItalic if enable is true; otherwise the style is set to QFont::StyleNormal. See also italic() and QFontInfo. void QFont::setKerning ( bool enable )Enables kerning for this font if enable 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 also kerning() and QFontMetrics. void QFont::setLetterSpacing ( SpacingType type, qreal spacing )Sets the letter spacing for the font to spacing and the type of spacing to type. 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. Эта функция была введена в Qt 4.4. See also letterSpacing(), letterSpacingType(), and setWordSpacing(). void QFont::setOverline ( bool enable )If enable is true, sets overline on; otherwise sets overline off. See also overline() and QFontInfo. void QFont::setPixelSize ( int pixelSize )Sets the font size to pixelSize pixels. Using this function makes the font device dependent. Use setPointSize() or setPointSizeF() to set the size of the font in a device independent manner. See also pixelSize(). void QFont::setPointSize ( int pointSize )Sets the point size to pointSize. The point size must be greater than zero. See also pointSize() and setPointSizeF(). void QFont::setPointSizeF ( qreal pointSize )Sets the point size to pointSize. The point size must be greater than zero. The requested precision may not be achieved on all platforms. See also pointSizeF(), setPointSize(), and setPixelSize(). void QFont::setRawMode ( bool enable )If enable 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 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 )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 as name to this function. 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 )Sets the stretch factor for the font. 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::Stretch. void QFont::setStrikeOut ( bool enable )If enable is true, sets strikeout on; otherwise sets strikeout off. See also strikeOut() and QFontInfo. void QFont::setStyle ( Style style )Sets the style of the font to style. See also style(), italic(), and QFontInfo. void QFont::setStyleHint ( StyleHint hint, StyleStrategy strategy = PreferDefault )Sets the style hint and strategy to hint and strategy, respectively. 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. void QFont::setStyleName ( const QString & styleName )Sets the style name of the font to the given styleName. When set, other style properties like style() and weight() will be ignored for font matching. Эта функция была введена в Qt 4.8. See also styleName(). void QFont::setStyleStrategy ( StyleStrategy s )Sets the style strategy for the font to s. See also styleStrategy() and QFont::StyleStrategy. void QFont::setUnderline ( bool enable )If enable is true, sets underline on; otherwise sets underline off. See also underline() and QFontInfo. void QFont::setWeight ( int weight )Sets the weight the font to weight, which should be a value from the QFont::Weight enumeration. See also weight() and QFontInfo. void QFont::setWordSpacing ( qreal spacing )Sets the word spacing for the font to spacing. 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. Эта функция была введена в Qt 4.4. See also wordSpacing() and setLetterSpacing(). int QFont::stretch () constReturns the stretch factor for the font. See also setStretch(). bool QFont::strikeOut () constReturns true if strikeout has been set; otherwise returns false. See also setStrikeOut(). Style QFont::style () constReturns the style of the font. Смотрите также setStyle(). StyleHint QFont::styleHint () constReturns the StyleHint. The style hint affects the font matching algorithm. See QFont::StyleHint for the list of available hints. See also setStyleHint(), QFont::StyleStrategy, and QFontInfo::styleHint(). QString QFont::styleName () constReturns 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. Эта функция была введена в Qt 4.8. See also setStyleName(), setFamily(), and setStyle(). StyleStrategy QFont::styleStrategy () constReturns the StyleStrategy. The style strategy affects the font matching algorithm. See QFont::StyleStrategy for the list of available strategies. See also setStyleStrategy(), setStyleHint(), and QFont::StyleHint. QString QFont::substitute ( const QString & familyName ) [static]Returns the first family name to be used whenever familyName is specified. The lookup is case insensitive. 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]Returns a list of family names to be used whenever familyName is specified. The lookup is case insensitive. If there is no substitution for familyName, an empty list is returned. See also substitute(), insertSubstitutions(), insertSubstitution(), and removeSubstitution(). QStringList QFont::substitutions () [static]Returns a sorted list of substituted family names. See also insertSubstitution(), removeSubstitution(), and substitute(). QString QFont::toString () constReturns a description of the font. The description is a comma-separated list of the attributes, perfectly suited for use in QSettings. See also fromString(). bool QFont::underline () constReturns true if underline has been set; otherwise returns false. Смотрите такжеsetUnderline(). int QFont::weight () constReturns the weight of the font which is one of the enumerated values from QFont::Weight. See also setWeight(), Weight, and QFontInfo. qreal QFont::wordSpacing () constReturns the word spacing for the font. Эта функция была введена в Qt 4.4. See also setWordSpacing() and setLetterSpacing(). QFont::operator QVariant () constReturns the font as a QVariant bool QFont::operator!= ( const QFont & f ) constReturns true if this font is different from f; otherwise returns false. 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. Смотрите также operator==(). bool QFont::operator< ( const QFont & f ) constProvides an arbitrary comparison of this font and font f. 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 use QFont objects as keys in a QMap. See also operator==(), operator!=(), and isCopyOf(). QFont & QFont::operator= ( const QFont & font )Assigns font to this font and returns a reference to it. bool QFont::operator== ( const QFont & f ) constReturns true if this font is equal to f; otherwise returns false. 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(). Связанные нечлены классаQDataStream & operator<< ( QDataStream & s, const QFont & font )Writes the font font to the data stream s. (toString() writes to a text stream.) Смотрите также Формат операторов QDataStream. QDataStream & operator>> ( QDataStream & s, QFont & font )Reads the font font from the data stream s. (fromString() reads from a text stream.) Смотрите также Формат операторов QDataStream. |
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