QRawFont¶

PyQt5.QtGui.QRawFont

Description¶

The QRawFont class provides access to a single physical instance of a font.

Note: QRawFont is a low level class. For most purposes QFont is a more appropriate class.

Most commonly, when presenting text in a user interface, the exact fonts used to render the characters is to some extent unknown. This can be the case for several reasons: For instance, the actual, physical fonts present on the target system could be unexpected to the developers, or the text could contain user selected styles, sizes or writing systems that are not supported by font chosen in the code.

Therefore, Qt’s QFont class really represents a query for fonts. When text is interpreted, Qt will do its best to match the text to the query, but depending on the support, different fonts can be used behind the scenes.

For most use cases, this is both expected and necessary, as it minimizes the possibility of text in the user interface being undisplayable. In some cases, however, more direct control over the process might be useful. It is for these use cases the QRawFont class exists.

A QRawFont object represents a single, physical instance of a given font in a given pixel size. I.e. in the typical case it represents a set of TrueType or OpenType font tables and uses a user specified pixel size to convert metrics into logical pixel units. It can be used in combination with the QGlyphRun class to draw specific glyph indexes at specific positions, and also have accessors to some relevant data in the physical font.

QRawFont only provides support for the main font technologies: GDI and DirectWrite on Windows platforms, FreeType on Linux platforms and CoreText on macOS. For other font back-ends, the APIs will be disabled.

QRawFont can be constructed in a number of ways:

It can be constructed by calling QTextLayout::glyphs() or QTextFragment::glyphs(). The returned QGlyphs objects will contain QRawFont objects which represent the actual fonts used to render each portion of the text.
It can be constructed by passing a QFont object to fromFont(). The function will return a QRawFont object representing the font that will be selected as response to the QFont query and the selected writing system.
It can be constructed by passing a file name or QByteArray directly to the QRawFont constructor, or by calling loadFromFile() or loadFromData(). In this case, the font will not be registered in QFontDatabase, and it will not be available as part of regular font selection.

QRawFont is considered local to the thread in which it is constructed (either using a constructor, or by calling loadFromData() or loadFromFile()). The QRawFont cannot be moved to a different thread, but will have to be recreated in the thread in question.

Note: For the requirement of caching glyph indexes and font selections for static text to avoid reshaping and relayouting in the inner loop of an application, a better choice is the QStaticText class, since it optimizes the memory cost of the cache and also provides the possibility of paint engine specific caches for an additional speed-up.

Classes¶

LayoutFlags

Enums¶

AntialiasingType

This enum represents the different ways a glyph can be rasterized in the function alphaMapForGlyph().

Member	Value	Description
PixelAntialiasing	0	Will rasterize by measuring the coverage of the shape on whole pixels. The returned image contains the alpha values of each pixel based on the coverage of the glyph shape.
SubPixelAntialiasing	1	Will rasterize by measuring the coverage of each subpixel, returning a separate alpha value for each of the red, green and blue components of each pixel.

LayoutFlag

TODO

Member	Value	Description
KernedAdvances	TODO	TODO
SeparateAdvances	TODO	TODO
UseDesignMetrics	TODO	TODO

Methods¶

__init__(): Constructs an invalid QRawFont.

__init__(QRawFont): Creates a QRawFont which is a copy of other.

__init__(str, float, hintingPreference: HintingPreference = PreferDefaultHinting)

Constructs a QRawFont representing the font contained in the file referenced by fileName for the size (in pixels) given by pixelSize, and using the hinting preference specified by hintingPreference.

Note: The referenced file must contain a TrueType or OpenType font.

__init__(Union[QByteArray, bytes, bytearray], float, hintingPreference: HintingPreference = PreferDefaultHinting)

Constructs a QRawFont representing the font contained in the supplied fontData for the size (in pixels) given by pixelSize, and using the hinting preference specified by hintingPreference.

Note: The data must contain a TrueType or OpenType font.

advancesForGlyphIndexes(Iterable[int]) → List[QPointF]: TODO

advancesForGlyphIndexes(Iterable[int], Union[LayoutFlags, LayoutFlag]) → List[QPointF]: TODO

alphaMapForGlyph(int, antialiasingType: AntialiasingType = SubPixelAntialiasing, transform: QTransform = QTransform()) → QImage

This function returns a rasterized image of the glyph at the given glyphIndex in the underlying font, using the transform specified. If the QRawFont is not valid, this function will return an invalid QImage.

If the font is a color font, then the resulting image will contain the rendered glyph at the current pixel size. In this case, the antialiasingType will be ignored.

Otherwise, if antialiasingType is set to SubPixelAntialiasing, then the resulting image will be in Format_RGB32 and the RGB values of each pixel will represent the subpixel opacities of the pixel in the rasterization of the glyph. Otherwise, the image will be in the format of Format_Indexed8 and each pixel will contain the opacity of the pixel in the rasterization.

See also

pathForGlyph(), drawGlyphRun().

ascent() → float: TODO

averageCharWidth() → float: TODO

boundingRect(int) → QRectF: TODO

capHeight() → float: TODO

descent() → float: TODO

__eq__(QRawFont) → bool: TODO

familyName() → str: TODO

fontTable(str) → QByteArray: TODO

@staticmethod fromFont(QFont, writingSystem: WritingSystem = Any) → QRawFont

Fetches the physical representation based on a font query. The physical font returned is the font that will be preferred by Qt in order to display text in the selected writingSystem.

Warning: This function is potentially expensive and should not be called in performance sensitive code.

glyphIndexesForString(str) → List[int]: TODO

__hash__() → int: TODO

hintingPreference() → HintingPreference: TODO

isValid() → bool: Returns true if the QRawFont is valid and false otherwise.

leading() → float: TODO

lineThickness() → float: TODO

loadFromData(Union[QByteArray, bytes, bytearray], float, HintingPreference)

Replaces the current QRawFont with the font contained in the supplied fontData for the size (in pixels) given by pixelSize, and using the hinting preference specified by hintingPreference.

The fontData must contain a TrueType or OpenType font.

See also

loadFromFile().

loadFromFile(str, float, HintingPreference)

Replaces the current QRawFont with the contents of the file referenced by fileName for the size (in pixels) given by pixelSize, and using the hinting preference specified by hintingPreference.

The file must reference a TrueType or OpenType font.

See also

loadFromData().

maxCharWidth() → float: TODO

__ne__(QRawFont) → bool: TODO

pathForGlyph(int) → QPainterPath

This function returns the shape of the glyph at a given glyphIndex in the underlying font if the QRawFont is valid. Otherwise, it returns an empty QPainterPath.

The returned glyph will always be unhinted.

See also

alphaMapForGlyph().

pixelSize() → float: See also

setPixelSize().

setPixelSize(float): Sets the pixel size with which this font should be rendered to pixelSize.

See also

pixelSize().

style() → Style: TODO

styleName() → str: TODO

supportedWritingSystems() → List[WritingSystem]: TODO

supportsCharacter(int) → bool: TODO

supportsCharacter(str) → bool: TODO

swap(QRawFont): TODO

underlinePosition() → float: TODO

unitsPerEm() → float: TODO

weight() → int: TODO

xHeight() → float: TODO