QFontDatabase Class

The QFontDatabase class provides information about the fonts available in the underlying window system. More...

Header:	#include <QFontDatabase>
qmake:	QT += gui

• List of all members, including inherited members
• Obsolete members

Note: All functions in this class are thread-safe.

Public Types

enum	SystemFont { GeneralFont, FixedFont, TitleFont, SmallestReadableFont }
enum	WritingSystem { Any, Latin, Greek, Cyrillic, Armenian, …, Nko }

Public Functions

	QFontDatabase()
bool	bold(const QString &family, const QString &style) const
QStringList	families(QFontDatabase::WritingSystem writingSystem = Any) const
QFont	font(const QString &family, const QString &style, int pointSize) const
bool	isBitmapScalable(const QString &family, const QString &style = QString()) const
bool	isFixedPitch(const QString &family, const QString &style = QString()) const
bool	isPrivateFamily(const QString &family) const
bool	isScalable(const QString &family, const QString &style = QString()) const
bool	isSmoothlyScalable(const QString &family, const QString &style = QString()) const
bool	italic(const QString &family, const QString &style) const
QList<int>	pointSizes(const QString &family, const QString &styleName = QString())
QList<int>	smoothSizes(const QString &family, const QString &styleName)
QString	styleString(const QFont &font)
QString	styleString(const QFontInfo &fontInfo)
QStringList	styles(const QString &family) const
int	weight(const QString &family, const QString &style) const
QList<QFontDatabase::WritingSystem>	writingSystems() const
QList<QFontDatabase::WritingSystem>	writingSystems(const QString &family) const

Static Public Members

int	addApplicationFont(const QString &fileName)
int	addApplicationFontFromData(const QByteArray &fontData)
QStringList	applicationFontFamilies(int id)
bool	removeAllApplicationFonts()
bool	removeApplicationFont(int id)
QList<int>	standardSizes()
QFont	systemFont(QFontDatabase::SystemFont type)
QString	writingSystemName(QFontDatabase::WritingSystem writingSystem)
QString	writingSystemSample(QFontDatabase::WritingSystem writingSystem)

Detailed Description

The most common uses of this class are to query the database for the list of font families() and for the pointSizes() and styles() that are available for each family. An alternative to pointSizes() is smoothSizes() which returns the sizes at which a given family and style will look attractive.

If the font family is available from two or more foundries the foundry name is included in the family name; for example: "Helvetica [Adobe]" and "Helvetica [Cronyx]". When you specify a family, you can either use the old hyphenated "foundry-family" format or the bracketed "family [foundry]" format; for example: "Cronyx-Helvetica" or "Helvetica [Cronyx]". If the family has a foundry it is always returned using the bracketed format, as is the case with the value returned by families().

The font() function returns a QFont given a family, style and point size.

A family and style combination can be checked to see if it is italic() or bold(), and to retrieve its weight(). Similarly we can call isBitmapScalable(), isSmoothlyScalable(), isScalable() and isFixedPitch().

Use the styleString() to obtain a text version of a style.

The QFontDatabase class also supports some static functions, for example, standardSizes(). You can retrieve the description of a writing system using writingSystemName(), and a sample of characters in a writing system with writingSystemSample().

Example:

    QFontDatabase database;
    QTreeWidget fontTree;
    fontTree.setColumnCount(2);
    fontTree.setHeaderLabels(QStringList() << "Font" << "Smooth Sizes");

    const QStringList fontFamilies = database.families();
    for (const QString &family : fontFamilies) {
        QTreeWidgetItem *familyItem = new QTreeWidgetItem(&fontTree);
        familyItem->setText(0, family);

        const QStringList fontStyles = database.styles(family);
        for (const QString &style : fontStyles) {
            QTreeWidgetItem *styleItem = new QTreeWidgetItem(familyItem);
            styleItem->setText(0, style);

            QString sizes;
            const QList<int> smoothSizes = database.smoothSizes(family, style)
            for (int points : smoothSizes)
                sizes += QString::number(points) + ' ';

            styleItem->setText(1, sizes.trimmed());
        }
    }

This example gets the list of font families, the list of styles for each family, and the point sizes that are available for each combination of family and style, displaying this information in a tree view.

See also QFont, QFontInfo, QFontMetrics, and Character Map Example.

Member Type Documentation

enum QFontDatabase::SystemFont

Constant	Value	Description
QFontDatabase::GeneralFont	0	The default system font.
QFontDatabase::FixedFont	1	The fixed font that the system recommends.
QFontDatabase::TitleFont	2	The system standard font for titles.
QFontDatabase::SmallestReadableFont	3	The smallest readable system font.

This enum was introduced or modified in Qt 5.2.

enum QFontDatabase::WritingSystem

Constant	Value	Description
QFontDatabase::Any	0
QFontDatabase::Latin	1
QFontDatabase::Greek	2
QFontDatabase::Cyrillic	3
QFontDatabase::Armenian	4
QFontDatabase::Hebrew	5
QFontDatabase::Arabic	6
QFontDatabase::Syriac	7
QFontDatabase::Thaana	8
QFontDatabase::Devanagari	9
QFontDatabase::Bengali	10
QFontDatabase::Gurmukhi	11
QFontDatabase::Gujarati	12
QFontDatabase::Oriya	13
QFontDatabase::Tamil	14
QFontDatabase::Telugu	15
QFontDatabase::Kannada	16
QFontDatabase::Malayalam	17
QFontDatabase::Sinhala	18
QFontDatabase::Thai	19
QFontDatabase::Lao	20
QFontDatabase::Tibetan	21
QFontDatabase::Myanmar	22
QFontDatabase::Georgian	23
QFontDatabase::Khmer	24
QFontDatabase::SimplifiedChinese	25
QFontDatabase::TraditionalChinese	26
QFontDatabase::Japanese	27
QFontDatabase::Korean	28
QFontDatabase::Vietnamese	29
QFontDatabase::Symbol	30
QFontDatabase::Other	Symbol	(the same as Symbol)
QFontDatabase::Ogham	31
QFontDatabase::Runic	32
QFontDatabase::Nko	33

Member Function Documentation

QFontDatabase::QFontDatabase()

Creates a font database object.

[static] int QFontDatabase::addApplicationFont(const QString &fileName)

Loads the font from the file specified by fileName and makes it available to the application. An ID is returned that can be used to remove the font again with removeApplicationFont() or to retrieve the list of family names contained in the font.

The function returns -1 if the font could not be loaded.

Currently only TrueType fonts, TrueType font collections, and OpenType fonts are supported.

Note: Adding application fonts on Unix/X11 platforms without fontconfig is currently not supported.

This function was introduced in Qt 4.2.

See also addApplicationFontFromData(), applicationFontFamilies(), and removeApplicationFont().

[static] int QFontDatabase::addApplicationFontFromData(const QByteArray &fontData)

Loads the font from binary data specified by fontData and makes it available to the application. An ID is returned that can be used to remove the font again with removeApplicationFont() or to retrieve the list of family names contained in the font.

The function returns -1 if the font could not be loaded.

Currently only TrueType fonts and TrueType font collections are supported.

Note: Adding application fonts on Unix/X11 platforms without fontconfig is currently not supported.

This function was introduced in Qt 4.2.

See also addApplicationFont(), applicationFontFamilies(), and removeApplicationFont().

[static] QStringList QFontDatabase::applicationFontFamilies(int id)

Returns a list of font families for the given application font identified by id.

This function was introduced in Qt 4.2.

See also addApplicationFont() and addApplicationFontFromData().

bool QFontDatabase::bold(const QString &family, const QString &style) const

Returns true if the font that has family family and style style is bold; otherwise returns false.

See also italic() and weight().

QStringList QFontDatabase::families(QFontDatabase::WritingSystem writingSystem = Any) const

Returns a sorted list of the available font families which support the writingSystem.

If a family exists in several foundries, the returned name for that font is in the form "family [foundry]". Examples: "Times [Adobe]", "Times [Cronyx]", "Palatino".

See also writingSystems().

QFont QFontDatabase::font(const QString &family, const QString &style, int pointSize) const

Returns a QFont object that has family family, style style and point size pointSize. If no matching font could be created, a QFont object that uses the application's default font is returned.

bool QFontDatabase::isBitmapScalable(const QString &family, const QString &style = QString()) const

Returns true if the font that has family family and style style is a scalable bitmap font; otherwise returns false. Scaling a bitmap font usually produces an unattractive hardly readable result, because the pixels of the font are scaled. If you need to scale a bitmap font it is better to scale it to one of the fixed sizes returned by smoothSizes().

See also isScalable() and isSmoothlyScalable().

bool QFontDatabase::isFixedPitch(const QString &family, const QString &style = QString()) const

Returns true if the font that has family family and style style is fixed pitch; otherwise returns false.

bool QFontDatabase::isPrivateFamily(const QString &family) const

Returns true if and only if the family font family is private.

This happens, for instance, on macOS and iOS, where the system UI fonts are not accessible to the user. For completeness, QFontDatabase::families() returns all font families, including the private ones. You should use this function if you are developing a font selection control in order to keep private fonts hidden.

This function was introduced in Qt 5.5.

See also families().

bool QFontDatabase::isScalable(const QString &family, const QString &style = QString()) const

Returns true if the font that has family family and style style is scalable; otherwise returns false.

See also isBitmapScalable() and isSmoothlyScalable().

bool QFontDatabase::isSmoothlyScalable(const QString &family, const QString &style = QString()) const

Returns true if the font that has family family and style style is smoothly scalable; otherwise returns false. If this function returns true, it's safe to scale this font to any size, and the result will always look attractive.

See also isScalable() and isBitmapScalable().

bool QFontDatabase::italic(const QString &family, const QString &style) const

Returns true if the font that has family family and style style is italic; otherwise returns false.

See also weight() and bold().

QList<int> QFontDatabase::pointSizes(const QString &family, const QString &styleName = QString())

Returns a list of the point sizes available for the font that has family family and style styleName. The list may be empty.

See also smoothSizes() and standardSizes().

[static] bool QFontDatabase::removeAllApplicationFonts()

Removes all application-local fonts previously added using addApplicationFont() and addApplicationFontFromData().

Returns true if unloading of the fonts succeeded; otherwise returns false.

This function was introduced in Qt 4.2.

See also removeApplicationFont(), addApplicationFont(), and addApplicationFontFromData().

[static] bool QFontDatabase::removeApplicationFont(int id)

Removes the previously loaded application font identified by id. Returns true if unloading of the font succeeded; otherwise returns false.

This function was introduced in Qt 4.2.

See also removeAllApplicationFonts(), addApplicationFont(), and addApplicationFontFromData().

QList<int> QFontDatabase::smoothSizes(const QString &family, const QString &styleName)

Returns the point sizes of a font that has family family and style styleName that will look attractive. The list may be empty. For non-scalable fonts and bitmap scalable fonts, this function is equivalent to pointSizes().

See also pointSizes() and standardSizes().

[static] QList<int> QFontDatabase::standardSizes()

Returns a list of standard font sizes.

See also smoothSizes() and pointSizes().

QString QFontDatabase::styleString(const QFont &font)

Returns a string that describes the style of the font. For example, "Bold Italic", "Bold", "Italic" or "Normal". An empty string may be returned.

QString QFontDatabase::styleString(const QFontInfo &fontInfo)

Returns a string that describes the style of the fontInfo. For example, "Bold Italic", "Bold", "Italic" or "Normal". An empty string may be returned.

QStringList QFontDatabase::styles(const QString &family) const

Returns a list of the styles available for the font family family. Some example styles: "Light", "Light Italic", "Bold", "Oblique", "Demi". The list may be empty.

See also families().

[static] QFont QFontDatabase::systemFont(QFontDatabase::SystemFont type)

Returns the most adequate font for a given type case for proper integration with the system's look and feel.

This function was introduced in Qt 5.2.

See also QGuiApplication::font().

int QFontDatabase::weight(const QString &family, const QString &style) const

Returns the weight of the font that has family family and style style. If there is no such family and style combination, returns -1.

See also italic() and bold().

[static] QString QFontDatabase::writingSystemName(QFontDatabase::WritingSystem writingSystem)

Returns the names the writingSystem (e.g. for displaying to the user in a dialog).

[static] QString QFontDatabase::writingSystemSample(QFontDatabase::WritingSystem writingSystem)

Returns a string with sample characters from writingSystem.

QList<QFontDatabase::WritingSystem> QFontDatabase::writingSystems() const

Returns a sorted list of the available writing systems. This is list generated from information about all installed fonts on the system.

See also families().

QList<QFontDatabase::WritingSystem> QFontDatabase::writingSystems(const QString &family) const

Returns a sorted list of the writing systems supported by a given font family.

See also families().