class QRawFont¶

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

Synopsis¶

Methods¶

def __init__()
def advancesForGlyphIndexes()
def alphaMapForGlyph()
def ascent()
def averageCharWidth()
def boundingRect()
def capHeight()
def descent()
def familyName()
def fontTable()
def glyphIndexesForString()
def hintingPreference()
def isValid()
def leading()
def lineThickness()
def loadFromData()
def loadFromFile()
def maxCharWidth()
def __ne__()
def __eq__()
def pathForGlyph()
def pixelSize()
def setPixelSize()
def style()
def styleName()
def supportedWritingSystems()
def supportsCharacter()
def swap()
def underlinePosition()
def unitsPerEm()
def weight()
def xHeight()

Static functions¶

def fromFont()

Note

This documentation may contain snippets that were automatically translated from C++ to Python. We always welcome contributions to the snippet translation. If you see an issue with the translation, you can also let us know by creating a ticket on https:/bugreports.qt.io/projects/PYSIDE

Detailed Description¶

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.

class AntialiasingType¶

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

Constant

Description

QRawFont.PixelAntialiasing

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.

QRawFont.SubPixelAntialiasing

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.

Constant	Description
QRawFont.PixelAntialiasing	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.
QRawFont.SubPixelAntialiasing	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.

class LayoutFlag¶

(inherits enum.Flag) This enum tells the function advancesForGlyphIndexes() how to calculate the advances.

Constant

Description

QRawFont.SeparateAdvances

Will calculate the advance for each glyph separately.

QRawFont.KernedAdvances

Will apply kerning between adjacent glyphs. Note that OpenType GPOS based kerning is currently not supported.

QRawFont.UseDesignMetrics

Use design metrics instead of hinted metrics adjusted to the resolution of the paint device. Can be OR-ed with any of the options above.

Constant	Description
QRawFont.SeparateAdvances	Will calculate the advance for each glyph separately.
QRawFont.KernedAdvances	Will apply kerning between adjacent glyphs. Note that OpenType GPOS based kerning is currently not supported.
QRawFont.UseDesignMetrics	Use design metrics instead of hinted metrics adjusted to the resolution of the paint device. Can be OR-ed with any of the options above.

__init__()¶

Constructs an invalid QRawFont .

__init__(other)

Parameters:: other – QRawFont

Creates a QRawFont which is a copy of other.

__init__(fontData, pixelSize[, hintingPreference=QFont.PreferDefaultHinting])

Parameters:

fontData – QByteArray
pixelSize – float
hintingPreference – HintingPreference

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.

__init__(fileName, pixelSize[, hintingPreference=QFont.PreferDefaultHinting])

Parameters:

fileName – str
pixelSize – float
hintingPreference – HintingPreference

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.

advancesForGlyphIndexes(glyphIndexes)¶

Parameters:: glyphIndexes – .list of quint32
Return type:: .list of QPointF

This is an overloaded function.

Returns the QRawFont ‘s advances for each of the glyphIndexes in pixel units. The advances give the distance from the position of a given glyph to where the next glyph should be drawn to make it appear as if the two glyphs are unspaced. The advance of each glyph is calculated separately.

See also

horizontalAdvance() horizontalAdvance()

advancesForGlyphIndexes(glyphIndexes, layoutFlags)

Parameters:

glyphIndexes – .list of quint32
layoutFlags – Combination of LayoutFlag

Return type:

.list of QPointF

Returns the QRawFont ‘s advances for each of the glyphIndexes in pixel units. The advances give the distance from the position of a given glyph to where the next glyph should be drawn to make it appear as if the two glyphs are unspaced. How the advances are calculated is controlled by layoutFlags.

Note

When KernedAdvances is requested, this function will apply kerning rules from the TrueType table KERN, if this is available in the font. In many modern fonts, kerning is handled through OpenType rules or AAT rules, which requires a full shaping step to be applied. To get the results of fully shaping the text, use QTextLayout .