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:

• family (str or unicode) – a font family name
• slant – the FONT_SLANT of the font, defaults to cairo.FONT_SLANT_NORMAL.
• weight – the FONT_WEIGHT of the font, defaults to cairo.FONT_WEIGHT_NORMAL.

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

New in version 1.8.4.

get_weight()

Returns:the FONT_WEIGHT value

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()

Not implemented in pycairo (yet)

get_font_face()

Returns:the FontFace that this ScaledFont was created for.

New in version 1.2.

get_font_matrix()

Not implemented in pycairo (yet)

get_font_options()

Not implemented in pycairo (yet)

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()

Not implemented in pycairo (yet)

text_extents(text)

Parameters:text (str or unicode) – text Returns:(x_bearing, y_bearing, width, height, x_advance, y_advance) Return type:6-tuple of float

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()

Not implemented in pycairo (yet)

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.

get_antialias()

Returns:the ANTIALIAS mode for the FontOptions object

get_hint_metrics()

Returns:the HINT METRICS mode for the FontOptions object

get_hint_style()

Returns:the HINT STYLE for the FontOptions object

get_subpixel_order()

Returns:the SUBPIXEL_ORDER for the FontOptions object

set_antialias(antialias)

Parameters:antialias – the ANTIALIAS mode

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

set_hint_metrics(hint_metrics)

Parameters:hint_metrics – the HINT METRICS mode

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

set_hint_style(hint_style)

Parameters:hint_style – 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 – 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.