QFontDatabase 类

QFontDatabase 类提供底层窗口系统中可用字体的有关信息。更多...

头：	`#include <QFontDatabase>`
CMake:	`find_package(Qt6 REQUIRED COMPONENTS Gui)` `target_link_libraries(mytarget PRIVATE Qt6::Gui)`
qmake:	`QT += gui`

注意： 此类的所有函数 thread-safe .

公共类型

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

静态公共成员

`(从 6.8 起)` void	addApplicationFallbackFontFamily (QChar::Script script , const QString & familyName )
int	addApplicationFont (const QString & fileName )
int	addApplicationFontFromData (const QByteArray & fontData )
`(从 6.8 起)` QStringList	applicationFallbackFontFamilies (QChar::Script script )
QStringList	applicationFontFamilies (int id )
bool	bold (const QString & family , const QString & style )
QStringList	families (QFontDatabase::WritingSystem writingSystem = Any)
QFont	font (const QString & family , const QString & style , int pointSize )
bool	isBitmapScalable (const QString & family , const QString & style = QString())
bool	isFixedPitch (const QString & family , const QString & style = QString())
bool	isPrivateFamily (const QString & family )
bool	isScalable (const QString & family , const QString & style = QString())
bool	isSmoothlyScalable (const QString & family , const QString & style = QString())
bool	italic (const QString & family , const QString & style )
QList<int>	pointSizes (const QString & family , const QString & styleName = QString())
bool	removeAllApplicationFonts ()
`(从 6.8 起)` bool	removeApplicationFallbackFontFamily (QChar::Script script , const QString & familyName )
bool	removeApplicationFont (int id )
`(从 6.8 起)` void	setApplicationFallbackFontFamilies (QChar::Script script , const QStringList & familyNames )
QList<int>	smoothSizes (const QString & family , const QString & styleName )
QList<int>	standardSizes ()
QString	styleString (const QFont & font )
QString	styleString (const QFontInfo & fontInfo )
QStringList	styles (const QString & family )
QFont	systemFont (QFontDatabase::SystemFont type )
int	weight (const QString & family , const QString & style )
QString	writingSystemName (QFontDatabase::WritingSystem writingSystem )
QString	writingSystemSample (QFontDatabase::WritingSystem writingSystem )
QList<QFontDatabase::WritingSystem>	writingSystems ()
QList<QFontDatabase::WritingSystem>	writingSystems (const QString & family )

详细描述

此类的最常见用法是查询数据库为列表字体 families () 和为 pointSizes () 和 styles () 可用于各系列。替代 pointSizes () 是 smoothSizes () 返回给定系列的大小且风格看起来很有吸引力。

若字体系列可用于两个或更多铸造厂，则铸造厂名包括在系列名中；例如：Helvetica [Adobe] 和 Helvetica [Cronyx]。当指定系列时，可以使用以连字符连接的旧 foundry-family 格式，或括在方括号内的 family [foundry] 格式；例如：Cronyx-Helvetica 或 Helvetica [Cronyx]。若有铸造厂，系列始终使用括在方括号内的格式，情况就像值返回通过 families ().

The font () 函数返回 QFont 的给定系列、样式及点大小。

可以校验系列和风格的组合，看它是否为 italic () 或 bold ()，及检索其 weight ()。同样，可以调用 isBitmapScalable (), isSmoothlyScalable (), isScalable () 和 isFixedPitch ().

使用 styleString () 以获取样式的文本版本。

QFontDatabase 类提供了一些帮手函数，例如 standardSizes ()。可以检索书写系统的描述使用 writingSystemName ()，和书写系统的字符样本采用 writingSystemSample ().

范例：

QTreeWidget fontTree;
fontTree.setColumnCount(2);
fontTree.setHeaderLabels(QStringList() << "Font" << "Smooth Sizes");
const QStringList fontFamilies = QFontDatabase::families();
for (const QString &family : fontFamilies) {
    QTreeWidgetItem *familyItem = new QTreeWidgetItem(&fontTree);
    familyItem->setText(0, family);
    const QStringList fontStyles = QFontDatabase::styles(family);
    for (const QString &style : fontStyles) {
        QTreeWidgetItem *styleItem = new QTreeWidgetItem(familyItem);
        styleItem->setText(0, style);
        QString sizes;
        const QList<int> smoothSizes = QFontDatabase::smoothSizes(family, style);
        for (const auto &points : smoothSizes)
            sizes += QString::number(points) + ' ';
        styleItem->setText(1, sizes.trimmed());
    }
}

此范例获取字体系列的列表，各系列的样式列表，及可用于系列和样式的各组合的点大小，在树视图中显示此信息。

另请参阅 QFont , QFontInfo ，和 QFontMetrics .

成员类型文档编制

enum QFontDatabase:: SystemFont

常量	值	描述
`QFontDatabase::GeneralFont`	`0`	默认系统字体。
`QFontDatabase::FixedFont`	`1`	系统推荐的固定字体。
`QFontDatabase::TitleFont`	`2`	用于标题的系统标准字体。
`QFontDatabase::SmallestReadableFont`	`3`	最小可读系统字体。

enum QFontDatabase:: WritingSystem

常量	值	描述
`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`	(如同 Symbol)
`QFontDatabase::Ogham`	`31`
`QFontDatabase::Runic`	`32`
`QFontDatabase::Nko`	`33`

成员函数文档编制

`[static, since 6.8]` void QFontDatabase:: addApplicationFallbackFontFamily ( QChar::Script script , const QString & familyName )

添加 familyName as an application-defined fallback font for script .

When Qt encounters characters that are not supported by the selected font, it will search through a list of fallback fonts to find a match for them. This ensures that combining multiple scripts in a single string is possible, even if the main font does not support them.

The list of fallback fonts is selected based on the script of the string as well as other conditions, such as system language.

While the system fallback list is usually sufficient, there are cases where it is useful to override the default behavior. One such case is for using application fonts as fallback to ensure cross-platform consistency.

In another case the application may be written in a script with regional differences and want to run it untranslated in multiple regions. In this case, it might be useful to override the local region's fallback with one that matches the language of the application.

By passing familyName to addApplicationFallbackFontFamily(), this will become the preferred family when matching missing characters from script 。 script must be a valid script ( QChar::Script_Latin or higher). When adding multiple fonts for the same script, they will be prioritized in reverse order, so that the last family added will be checked first and so on.

注意： Qt's font matching algorithm considers QChar::Script_Common (undetermined script) and QChar::Script_Latin the same. Adding a fallback for either of these will also apply to the other.

该函数在 Qt 6.8 引入。

另请参阅 setApplicationFallbackFontFamilies (), removeApplicationFallbackFontFamily ()，和 applicationFallbackFontFamilies ().

`[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.

函数返回 -1，若无法加载字体。

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

另请参阅 addApplicationFontFromData (), applicationFontFamilies ()，和 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.

函数返回 -1，若无法加载字体。

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

另请参阅 addApplicationFont (), applicationFontFamilies ()，和 removeApplicationFont ().

`[static, since 6.8]` QStringList QFontDatabase:: applicationFallbackFontFamilies ( QChar::Script script )

Returns the list of application-defined fallback font families previously added for script 通过 addApplicationFallbackFontFamily () 函数。

该函数在 Qt 6.8 引入。

另请参阅 setApplicationFallbackFontFamilies (), addApplicationFallbackFontFamily ()，和 removeApplicationFallbackFontFamily ().

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

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

另请参阅 addApplicationFont () 和 addApplicationFontFromData ().

`[static]` bool QFontDatabase:: bold (const QString & family , const QString & style )

返回 true 若字体拥有系列 family 和样式 style 为加粗；否则返回 false .

另请参阅 italic () 和 weight ().

`[static]` QStringList QFontDatabase:: families ( QFontDatabase::WritingSystem writingSystem = Any)

返回可用字体系列的排序列表，支持 writingSystem .

若系列存在于几个铸造厂，则该字体的返回名称形式为 family [foundry]。范例：Times [Adobe]、Times [Cronyx]、Palatino。

另请参阅 writingSystems ().

`[static]` QFont QFontDatabase:: font (const QString & family , const QString & style , int pointSize )

返回 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.

`[static]` bool QFontDatabase:: isBitmapScalable (const QString & family , const QString & style = QString())

返回 true 若字体拥有系列 family 和样式 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 ().

另请参阅 isScalable () 和 isSmoothlyScalable ().

`[static]` bool QFontDatabase:: isFixedPitch (const QString & family , const QString & style = QString())

返回 true 若字体拥有系列 family 和样式 style is fixed pitch; otherwise returns false .

`[static]` bool QFontDatabase:: isPrivateFamily (const QString & family )

返回 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.

另请参阅 families ().

`[static]` bool QFontDatabase:: isScalable (const QString & family , const QString & style = QString())

返回 true 若字体拥有系列 family 和样式 style is scalable; otherwise returns false .

另请参阅 isBitmapScalable () 和 isSmoothlyScalable ().

`[static]` bool QFontDatabase:: isSmoothlyScalable (const QString & family , const QString & style = QString())

返回 true 若字体拥有系列 family 和样式 style is smoothly scalable; otherwise returns false 。若此函数返回 true , it's safe to scale this font to any size, and the result will always look attractive.

另请参阅 isScalable () 和 isBitmapScalable ().

`[static]` bool QFontDatabase:: italic (const QString & family , const QString & style )

返回 true 若字体拥有系列 family 和样式 style 为斜体；否则返回 false .

另请参阅 weight () 和 bold ().

`[static]` 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 和样式 styleName . The list may be empty.

另请参阅 smoothSizes () 和 standardSizes ().

`[static]` bool QFontDatabase:: removeAllApplicationFonts ()

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

返回 true 若字体卸载成功；否则返回 false .

另请参阅 removeApplicationFont (), addApplicationFont ()，和 addApplicationFontFromData ().

`[static, since 6.8]` bool QFontDatabase:: removeApplicationFallbackFontFamily ( QChar::Script script , const QString & familyName )

移除 familyName from the list of application-defined fallback fonts for script , provided that it has previously been added with addApplicationFallbackFontFamily ().

Returns true if the family name was in the list and false if it was not.

该函数在 Qt 6.8 引入。

另请参阅 addApplicationFallbackFontFamily (), setApplicationFallbackFontFamilies ()，和 applicationFallbackFontFamilies ().

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

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

另请参阅 removeAllApplicationFonts (), addApplicationFont ()，和 addApplicationFontFromData ().

`[static, since 6.8]` void QFontDatabase:: setApplicationFallbackFontFamilies ( QChar::Script script , const QStringList & familyNames )

Sets the list of application-defined fallback fonts for script to familyNames .

When Qt encounters a character in script which is not supported by the current font, it will check the families in familyNames , in order from first to last, until it finds a match. See addApplicationFallbackFontFamily () 了解更多细节。

This function overwrites the current list of application-defined fallback fonts for script .

该函数在 Qt 6.8 引入。

另请参阅 addApplicationFallbackFontFamily (), removeApplicationFallbackFontFamily ()，和 applicationFallbackFontFamilies ().

`[static]` QList < int > QFontDatabase:: smoothSizes (const QString & family , const QString & styleName )

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

另请参阅 pointSizes () 和 standardSizes ().

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

返回标准字体大小的列表。

另请参阅 smoothSizes () 和 pointSizes ().

`[static]` 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.

`[static]` 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.

`[static]` QStringList QFontDatabase:: styles (const QString & family )

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.

另请参阅 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.

另请参阅 QGuiApplication::font ().

`[static]` int QFontDatabase:: weight (const QString & family , const QString & style )

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

另请参阅 italic () 和 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 .

`[static]` QList < QFontDatabase::WritingSystem > QFontDatabase:: writingSystems ()

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

另请参阅 families ().

`[static]` QList < QFontDatabase::WritingSystem > QFontDatabase:: writingSystems (const QString & family )

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

另请参阅 families ().

QFontDatabase 类

公共类型

静态公共成员

详细描述

成员类型文档编制

enum QFontDatabase:: SystemFont

enum QFontDatabase:: WritingSystem

成员函数文档编制

[static, since 6.8] void QFontDatabase:: addApplicationFallbackFontFamily ( QChar::Script script , const QString & familyName )

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

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

[static, since 6.8] QStringList QFontDatabase:: applicationFallbackFontFamilies ( QChar::Script script )

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

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

[static] QStringList QFontDatabase:: families ( QFontDatabase::WritingSystem writingSystem = Any)

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

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

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

[static] bool QFontDatabase:: isPrivateFamily (const QString & family )

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

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

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

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

[static] bool QFontDatabase:: removeAllApplicationFonts ()

[static, since 6.8] bool QFontDatabase:: removeApplicationFallbackFontFamily ( QChar::Script script , const QString & familyName )

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

[static, since 6.8] void QFontDatabase:: setApplicationFallbackFontFamilies ( QChar::Script script , const QStringList & familyNames )

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

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

[static] QString QFontDatabase:: styleString (const QFont & font )

[static] QString QFontDatabase:: styleString (const QFontInfo & fontInfo )

[static] QStringList QFontDatabase:: styles (const QString & family )

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

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

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

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

[static] QList < QFontDatabase::WritingSystem > QFontDatabase:: writingSystems ()

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

内容

`[static, since 6.8]` void QFontDatabase:: addApplicationFallbackFontFamily ( QChar::Script script , const QString & familyName )

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

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

`[static, since 6.8]` QStringList QFontDatabase:: applicationFallbackFontFamilies ( QChar::Script script )

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

`[static]` bool QFontDatabase:: bold (const QString & family , const QString & style )

`[static]` QStringList QFontDatabase:: families ( QFontDatabase::WritingSystem writingSystem = Any)

`[static]` QFont QFontDatabase:: font (const QString & family , const QString & style , int pointSize )

`[static]` bool QFontDatabase:: isBitmapScalable (const QString & family , const QString & style = QString())

`[static]` bool QFontDatabase:: isFixedPitch (const QString & family , const QString & style = QString())

`[static]` bool QFontDatabase:: isPrivateFamily (const QString & family )

`[static]` bool QFontDatabase:: isScalable (const QString & family , const QString & style = QString())

`[static]` bool QFontDatabase:: isSmoothlyScalable (const QString & family , const QString & style = QString())

`[static]` bool QFontDatabase:: italic (const QString & family , const QString & style )

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

`[static]` bool QFontDatabase:: removeAllApplicationFonts ()

`[static, since 6.8]` bool QFontDatabase:: removeApplicationFallbackFontFamily ( QChar::Script script , const QString & familyName )

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

`[static, since 6.8]` void QFontDatabase:: setApplicationFallbackFontFamilies ( QChar::Script script , const QStringList & familyNames )

`[static]` QList < int > QFontDatabase:: smoothSizes (const QString & family , const QString & styleName )

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

`[static]` QString QFontDatabase:: styleString (const QFont & font )

`[static]` QString QFontDatabase:: styleString (const QFontInfo & fontInfo )

`[static]` QStringList QFontDatabase:: styles (const QString & family )

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

`[static]` int QFontDatabase:: weight (const QString & family , const QString & style )

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

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

`[static]` QList < QFontDatabase::WritingSystem > QFontDatabase:: writingSystems ()

`[static]` QList < QFontDatabase::WritingSystem > QFontDatabase:: writingSystems (const QString & family )