Text

Cairo has two sets of text rendering capabilities:

  • The functions with text in their name form cairo’s toy text API. The toy API takes UTF-8 encoded text and is limited in its functionality to rendering simple left-to-right text with no advanced features. That means for example that most complex scripts like Hebrew, Arabic, and Indic scripts are out of question. No kerning or correct positioning of diacritical marks either. The font selection is pretty limited too and doesn’t handle the case that the selected font does not cover the characters in the text. This set of functions are really that, a toy text API, for testing and demonstration purposes. Any serious application should avoid them.
  • The functions with glyphs in their name form cairo’s low-level text API. The low-level API relies on the user to convert text to a set of glyph indexes and positions. This is a very hard problem and is best handled by external libraries, like the pangocairo that is part of the Pango text layout and rendering library. Pango is available from http://www.pango.org/.

class FontFace()

A cairo.FontFace specifies all aspects of a font other than the size or font matrix (a font matrix is used to distort a font by sheering it or scaling it unequally in the two directions). A FontFace can be set on a Context by using Context.set_font_face() the size and font matrix are set with Context.set_font_size() and Context.set_font_matrix().

There are various types of FontFace, depending on the font backend they use.

class cairo.FontFace

Note

This class cannot be instantiated directly, it is returned by Context.get_font_face().

class FreeTypeFontFace(FontFace)

FreeType Fonts - Font support for FreeType.

The FreeType font backend is primarily used to render text on GNU/Linux systems, but can be used on other platforms too.

Note

FreeType Fonts are not implemented in pycairo because there is no open source Python bindings to FreeType (and fontconfig) that provides a C API. This a possible project idea for anyone interested in adding FreeType support to pycairo.

class ToyFontFace(FontFace)

The cairo.ToyFontFace class can be used instead of Context.select_font_face() to create a toy font independently of a context.

class cairo.ToyFontFace(family[, slant[, weight]])
Parameters:
Returns:

a new ToyFontFace

Creates a ToyFontFace from a triplet of family, slant, and weight. These font faces are used in implementation of the the “toy” font API.

If family is the zero-length string “”, the platform-specific default family is assumed. The default family then can be queried using get_family().

The Context.select_font_face() method uses this to create font faces. See that function for limitations of toy font faces.

New in version 1.8.4.

get_family()
Returns:the family name of a toy font
Return type:str

New in version 1.8.4.

get_slant()
Returns:the font slant value
Return type:cairo.FontSlant

New in version 1.8.4.

get_weight()
Returns:the font weight value
Return type:cairo.FontWeight

New in version 1.8.4.

class UserFontFace(FontFace)

The user-font feature allows the cairo user to provide drawings for glyphs in a font. This is most useful in implementing fonts in non-standard formats, like SVG fonts and Flash fonts, but can also be used by games and other application to draw “funky” fonts.

Note

UserFontFace support has not (yet) been added to pycairo. If you need this feature in pycairo register your interest by sending a message to the cairo mailing list, or by opening a pycairo bug report.

class ScaledFont()

A ScaledFont is a font scaled to a particular size and device resolution. A ScaledFont is most useful for low-level font usage where a library or application wants to cache a reference to a scaled font to speed up the computation of metrics.

There are various types of scaled fonts, depending on the font backend they use.

class cairo.ScaledFont(font_face, font_matrix, ctm, options)
Parameters:
  • font_face – a FontFace instance
  • font_matrix – font space to user space transformation Matrix for the font. In the simplest case of a N point font, this matrix is just a scale by N, but it can also be used to shear the font or stretch it unequally along the two axes. See Context.set_font_matrix().
  • ctm – user to device transformation Matrix with which the font will be used.
  • options – a FontOptions instance to use when getting metrics for the font and rendering with it.

Creates a ScaledFont object from a FontFace and matrices that describe the size of the font and the environment in which it will be used.

extents()
Returns:(ascent, descent, height, max_x_advance, max_y_advance), a tuple of float values.

Gets the metrics for a ScaledFont.

get_ctm()
Returns:the CTM
Return type:cairo.Matrix

Returns the CTM with which scaled_font was created into ctm. Note that the translation offsets (x0, y0) of the CTM are ignored by ScaledFont(). So, the matrix this function returns always has 0, 0 as x0, y0.

New in version 1.12.0.

get_font_face()
Returns:the FontFace that this ScaledFont was created for.

New in version 1.2.

get_font_matrix()
Returns:the matrix
Return type:cairo.Matrix

Returns the font matrix with which scaled_font was created.

New in version 1.12.0.

get_font_options()
Returns:font options
Return type:cairo.FontOptions

Returns the font options with which scaled_font was created.

New in version 1.12.0.

get_scale_matrix()
Returns:the scale Matrix

The scale matrix is product of the font matrix and the ctm associated with the scaled font, and hence is the matrix mapping from font space to device space.

New in version 1.8.

glyph_extents(glyphs)
Parameters:glyphs – glyphs, a sequence of Glyph
Return type:TextExtents

New in version 1.15.

Gets the extents for a list of glyphs. The extents describe a user-space rectangle that encloses the “inked” portion of the glyphs, (as they would be drawn by Context.show_glyphs() if the cairo graphics state were set to the same font_face, font_matrix, ctm, and font_options as scaled_font ). Additionally, the x_advance and y_advance values indicate the amount by which the current point would be advanced by cairo_show_glyphs().

Note that whitespace glyphs do not contribute to the size of the rectangle (extents.width and extents.height).

text_extents(text)
Parameters:text (text) – text
Return type:TextExtents

Gets the extents for a string of text. The extents describe a user-space rectangle that encloses the “inked” portion of the text drawn at the origin (0,0) (as it would be drawn by Context.show_text() if the cairo graphics state were set to the same font_face, font_matrix, ctm, and font_options as ScaledFont). Additionally, the x_advance and y_advance values indicate the amount by which the current point would be advanced by Context.show_text().

Note that whitespace characters do not directly contribute to the size of the rectangle (width and height). They do contribute indirectly by changing the position of non-whitespace characters. In particular, trailing whitespace characters are likely to not affect the size of the rectangle, though they will affect the x_advance and y_advance values.

New in version 1.2.

text_to_glyphs(x, y, utf8[, with_clusters=True])
Parameters:
  • x (float) – X position to place first glyph
  • y (float) – Y position to place first glyph
  • utf8 (text) – a string of text
  • with_clusters (bool) – If False only the glyph list will computed and returned
Returns:

a tuple of ([Glyph], [TextCluster], TextClusterFlags)

Return type:

tuple

Raises:

Error

New in version 1.15.

Converts UTF-8 text to a list of glyphs, with cluster mapping, that can be used to render later.

For details of how clusters, and cluster_flags map input UTF-8 text to the output glyphs see Context.show_text_glyphs().

The output values can be readily passed to Context.show_text_glyphs() Context.show_glyphs(), or related functions, assuming that the exact same scaled font is used for the operation.

class FontOptions()

An opaque structure holding all options that are used when rendering fonts.

Individual features of a FontOptions can be set or accessed using functions named FontOptions.set_<feature_name> and FontOptions.get_<feature_name>, like FontOptions.set_antialias() and FontOptions.get_antialias().

New features may be added to a FontOptions in the future. For this reason, FontOptions.copy(), FontOptions.equal(), FontOptions.merge(), and FontOptions.hash() should be used to copy, check for equality, merge, or compute a hash value of FontOptions objects.

class cairo.FontOptions
Returns:a newly allocated FontOptions.

Allocates a new FontOptions object with all options initialized to default values.

Implements __eq__ and __ne__ using equal() since 1.12.0.

get_antialias()
Returns:the antialias mode for the FontOptions object
Return type:cairo.Antialias
get_hint_metrics()
Returns:the hint metrics mode for the FontOptions object
Return type:cairo.HintMetrics
get_hint_style()
Returns:the hint style for the FontOptions object
Return type:cairo.HintStyle
get_subpixel_order()
Returns:the subpixel order for the FontOptions object
Return type:cairo.SubpixelOrder
set_antialias(antialias)
Parameters:antialias (cairo.Antialias) – the antialias mode

This specifies the type of antialiasing to do when rendering text.

set_hint_metrics(hint_metrics)
Parameters:hint_metrics (cairo.HintMetrics) – the hint metrics mode

This controls whether metrics are quantized to integer values in device units.

set_hint_style(hint_style)
Parameters:hint_style (cairo.HintStyle) – the hint style

This controls whether to fit font outlines to the pixel grid, and if so, whether to optimize for fidelity or contrast.

set_subpixel_order(subpixel_order)
Parameters:subpixel_order (cairo.SubpixelOrder) – the subpixel order

The subpixel order specifies the order of color elements within each pixel on the display device when rendering with an antialiasing mode of cairo.Antialias.SUBPIXEL.

merge(other)
Parameters:other (FontOptions) – another FontOptions

Merges non-default options from other into options , replacing existing values. This operation can be thought of as somewhat similar to compositing other onto options with the operation of Operator.OVER.

New in version 1.12.0.

copy()
Returns:a new FontOptions

Returns a new font options object copying the option values from original.

New in version 1.12.0.

hash()
Returns:the hash value for the font options object
Return type:int

Compute a hash for the font options object; this value will be useful when storing an object containing a FontOptions in a hash table.

New in version 1.12.0.

equal(other)
param FontOptions other:
 another FontOptions
returns:True if all fields of the two font options objects match. Note that this function will return False if either object is in error.
rtype:bool

Compares two font options objects for equality.

New in version 1.12.0.

set_variations(variations)
Parameters:variations (str or None) – the new font variations, or None

Sets the OpenType font variations for the font options object. Font variations are specified as a string with a format that is similar to the CSS font-variation-settings. The string contains a comma-separated list of axis assignments, which each assignment consists of a 4-character axis name and a value, separated by whitespace and optional equals sign.

Examples:

  • wght=200,wdth=140.5
  • wght 200 , wdth 140.5

New in version 1.18.0: Only available with cairo 1.15.12+

get_variations()
Returns:the font variations for the font options object. The returned string belongs to the options and must not be modified. It is valid until either the font options object is destroyed or the font variations in this object is modified with set_variations().
Return type:str

Gets the OpenType font variations for the font options object. See set_variations() for details about the string format.

New in version 1.18.0: Only available with cairo 1.15.12+