Struct qt_gui::QFont

source ·

#[repr(C)]
pub struct QFont { /* private fields */ }

Expand description

The QFont class specifies a font used for drawing text.

C++ class: QFont.

C++ documentation:

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 QGuiApplication instance must exist before a QFont can be used. You can set the application's default font with QGuiApplication::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(), setPointSizeF(), 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 removeSubstitutions(). 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.

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:

The specified font family is searched for.
If not found, the styleHint() is used to select a replacement family.
Each replacement font family is searched for.
If none of these are found or there was no styleHint(), "helvetica" will be searched for.
If "helvetica" isn't found Qt will try the lastResortFamily().
If the lastResortFamily() isn't found Qt will try the lastResortFont() 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 the PreferBitmap style strategy (see setStyleStrategy()).

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

fixedPitch()
pointSize() (see below)
weight()
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. 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.

Struct qt_gui::QFont

Implementations§

impl QFont

pub unsafe fn bold(&self) -> bool

pub unsafe fn cache_statistics()

pub unsafe fn capitalization(&self) -> Capitalization

pub unsafe fn cleanup()

pub unsafe fn copy_from(&self, arg1: impl CastInto<Ref<QFont>>) -> Ref<QFont>

pub unsafe fn default_family(&self) -> CppBox<QString>

pub unsafe fn exact_match(&self) -> bool

pub unsafe fn families(&self) -> CppBox<QStringList>

pub unsafe fn family(&self) -> CppBox<QString>

pub unsafe fn fixed_pitch(&self) -> bool

pub unsafe fn from_string(&self, arg1: impl CastInto<Ref<QString>>) -> bool

pub unsafe fn hinting_preference(&self) -> HintingPreference

pub unsafe fn initialize()

pub unsafe fn insert_substitution( arg1: impl CastInto<Ref<QString>>, arg2: impl CastInto<Ref<QString>> )

pub unsafe fn insert_substitutions( arg1: impl CastInto<Ref<QString>>, arg2: impl CastInto<Ref<QStringList>> )

pub unsafe fn is_copy_of(&self, arg1: impl CastInto<Ref<QFont>>) -> bool

pub unsafe fn italic(&self) -> bool

pub unsafe fn kerning(&self) -> bool

pub unsafe fn key(&self) -> CppBox<QString>

pub unsafe fn last_resort_family(&self) -> CppBox<QString>

pub unsafe fn last_resort_font(&self) -> CppBox<QString>

pub unsafe fn letter_spacing(&self) -> c_double

pub unsafe fn letter_spacing_type(&self) -> SpacingType

pub unsafe fn new() -> CppBox<QFont>

pub unsafe fn from_q_string2_int_bool( family: impl CastInto<Ref<QString>>, point_size: c_int, weight: c_int, italic: bool ) -> CppBox<QFont>

pub unsafe fn from_q_font_q_paint_device( arg1: impl CastInto<Ref<QFont>>, pd: impl CastInto<Ptr<QPaintDevice>> ) -> CppBox<QFont>

pub unsafe fn from_q_string2_int( family: impl CastInto<Ref<QString>>, point_size: c_int, weight: c_int ) -> CppBox<QFont>

pub unsafe fn from_q_string_int( family: impl CastInto<Ref<QString>>, point_size: c_int ) -> CppBox<QFont>

pub unsafe fn from_q_string( family: impl CastInto<Ref<QString>> ) -> CppBox<QFont>

pub unsafe fn from_q_font_q_paint_device2( font: impl CastInto<Ref<QFont>>, pd: impl CastInto<Ptr<QPaintDevice>> ) -> CppBox<QFont>

pub unsafe fn new_copy(arg1: impl CastInto<Ref<QFont>>) -> CppBox<QFont>

pub unsafe fn overline(&self) -> bool

pub unsafe fn pixel_size(&self) -> c_int

pub unsafe fn point_size(&self) -> c_int

pub unsafe fn point_size_f(&self) -> c_double

pub unsafe fn raw_mode(&self) -> bool

pub unsafe fn raw_name(&self) -> CppBox<QString>

pub unsafe fn remove_substitutions(arg1: impl CastInto<Ref<QString>>)

pub unsafe fn resolve_1a( &self, arg1: impl CastInto<Ref<QFont>> ) -> CppBox<QFont>

pub unsafe fn resolve_0a(&self) -> c_uint

pub unsafe fn resolve_1a_mut(&self, mask: c_uint)

pub unsafe fn set_bold(&self, arg1: bool)

pub unsafe fn set_capitalization(&self, arg1: Capitalization)

pub unsafe fn set_families(&self, arg1: impl CastInto<Ref<QStringList>>)

pub unsafe fn set_family(&self, arg1: impl CastInto<Ref<QString>>)

pub unsafe fn set_fixed_pitch(&self, arg1: bool)

pub unsafe fn set_hinting_preference( &self, hinting_preference: HintingPreference )

pub unsafe fn set_italic(&self, b: bool)

pub unsafe fn set_kerning(&self, arg1: bool)

pub unsafe fn set_letter_spacing(&self, type_: SpacingType, spacing: c_double)

pub unsafe fn set_overline(&self, arg1: bool)

pub unsafe fn set_pixel_size(&self, arg1: c_int)

pub unsafe fn set_point_size(&self, arg1: c_int)

pub unsafe fn set_point_size_f(&self, arg1: c_double)

pub unsafe fn set_raw_mode(&self, arg1: bool)

pub unsafe fn set_raw_name(&self, arg1: impl CastInto<Ref<QString>>)

pub unsafe fn set_stretch(&self, arg1: c_int)

pub unsafe fn set_strike_out(&self, arg1: bool)

pub unsafe fn set_style(&self, style: Style)

pub unsafe fn set_style_hint_2a(&self, arg1: StyleHint, arg2: StyleStrategy)

pub unsafe fn set_style_hint_1a(&self, arg1: StyleHint)

pub unsafe fn set_style_name(&self, arg1: impl CastInto<Ref<QString>>)

pub unsafe fn set_style_strategy(&self, s: StyleStrategy)

pub unsafe fn set_underline(&self, arg1: bool)

pub unsafe fn set_weight(&self, arg1: c_int)

pub unsafe fn set_word_spacing(&self, spacing: c_double)

pub unsafe fn static_meta_object() -> Ref<QMetaObject>

pub unsafe fn stretch(&self) -> c_int

pub unsafe fn strike_out(&self) -> bool

pub unsafe fn style(&self) -> Style

pub unsafe fn style_hint(&self) -> StyleHint

pub unsafe fn style_name(&self) -> CppBox<QString>

pub unsafe fn style_strategy(&self) -> StyleStrategy

pub unsafe fn substitute(arg1: impl CastInto<Ref<QString>>) -> CppBox<QString>

pub unsafe fn substitutes( arg1: impl CastInto<Ref<QString>> ) -> CppBox<QStringList>

pub unsafe fn substitutions() -> CppBox<QStringList>

pub unsafe fn swap(&self, other: impl CastInto<Ref<QFont>>)

impl<T> Any for T
where T: 'static + ?Sized,

impl<T> Borrow<T> for T
where T: ?Sized,

impl<T> BorrowMut<T> for T
where T: ?Sized,

impl<T, U> CastInto<U> for T
where U: CastFrom<T>,

impl<T, U> Into<U> for T
where U: From<T>,

impl<T, U> TryFrom<U> for T
where U: Into<T>,

impl<T, U> TryInto<U> for T
where U: TryFrom<T>,