Text — Pycairo documentation

# 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()

class cairo.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.

  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`)

class cairo.ToyFontFace(family: str, slant: FontSlant = Ellipsis, weight: FontWeight = Ellipsis)

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

  New in version 1.8.4.

  __init__(family: str, slant: FontSlant = Ellipsis, weight: FontWeight = Ellipsis) → None
    Parameters:

      - family – a font family name

      - slant – the font slant of the font, defaults to `cairo.FontSlant.NORMAL`.

      - weight – the font weight of the font, defaults to `cairo.FontWeight.NORMAL`.

    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.

  get_family() → str
    Returns:

      the family name of a toy font

    New in version 1.8.4.

  get_slant() → FontSlant
    Returns:

      the font slant value

    New in version 1.8.4.

  get_weight() → FontWeight
    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()

class cairo.ScaledFont(font_face: FontFace, font_matrix: Matrix, ctm: Matrix, options: FontOptions)

  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.

  __init__(font_face: FontFace, font_matrix: Matrix, ctm: Matrix, options: FontOptions) → None
    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() → Tuple[float, float, float, float, float]

    Gets the metrics for a ScaledFont.

  get_ctm() → Matrix
    Returns:

      the CTM

    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() → FontFace
    Returns:

      the `FontFace` that this ScaledFont was created for.

    New in version 1.2.

  get_font_matrix() → Matrix
    Returns:

      the matrix

    Returns the font matrix with which scaled_font was created.

  get_font_options() → FontOptions
    Returns:

      font options

    Returns the font options with which scaled_font was created.

    New in version 1.12.0.

  get_scale_matrix() → 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: Sequence[Glyph]) → TextExtents
    Parameters:

      glyphs – glyphs, a sequence of `Glyph`

    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: str) → TextExtents
    Parameters:

      text – text

    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: float, y: float, utf8: str, with_clusters: bool = True) → Tuple[List[Glyph], List[TextCluster], TextClusterFlags] | List[Glyph]
    Parameters:

      - x – X position to place first glyph

      - y – Y position to place first glyph

      - utf8 – a string of text

      - with_clusters – If `False` only the glyph list will computed and returned

    Returns:

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

    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()

class cairo.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.

  Implements __eq__ and __ne__ using equal() since 1.12.0.

  __init__() → None

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

  get_antialias() → Antialias
    Returns:

      the antialias mode for the FontOptions object

  get_hint_style() → HintStyle
    Returns:

      the hint style for the FontOptions object

  get_subpixel_order() → SubpixelOrder
    Returns:

      the subpixel order for the FontOptions object

  set_antialias(antialias: Antialias) → None
    Parameters:

      antialias – the antialias mode

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

  set_hint_metrics(hint_metrics: HintMetrics) → None
    Parameters:

      hint_metrics – the hint metrics mode

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

  set_hint_style(hint_style: HintStyle) → None
    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.

  merge(other: FontOptions) → None
    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() → FontOptions
    Returns:

      a new `FontOptions`

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

    New in version 1.12.0.

  hash() → int
    Returns:

      the hash value for the font options object

    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: FontOptions) → bool
    Parameters:

      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.

    Compares two font options objects for equality.

    New in version 1.12.0.

  set_variations(variations: str | None) → None
    Parameters:

      variations – 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() → str
    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()`.

    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+

  get_hint_metrics() → HintMetrics
    Returns:

      the hint metrics mode for the FontOptions object

  set_subpixel_order(subpixel_order: SubpixelOrder) → None
    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`.

  set_color_mode(color_mode: ColorMode) → None
    Parameters:

      color_mode – the new color mode

    Sets the color mode for the font options object. This controls whether color fonts are to be rendered in color or as outlines. See the documentation for `ColorMode` for full details.

    New in version 1.25.0: Only available with cairo 1.17.8+

  get_color_mode() → ColorMode
    Returns:

      the color mode for the font options object

    Gets the color mode for the font options object. See the documentation for `ColorMode` for full details.

    New in version 1.25.0: Only available with cairo 1.17.8+

  set_color_palette(palette_index: int) → None
    Parameters:

      palette_index – the palette index in the CPAL table

    Sets the OpenType font color palette for the font options object. OpenType color fonts with a CPAL table may contain multiple palettes. The default color palette index is `COLOR_PALETTE_DEFAULT`. If palette_index is invalid, the default palette is used.

    New in version 1.25.0: Only available with cairo 1.17.8+

  get_color_palette() → int
    Returns:

      the palette index

    Gets the OpenType color font palette for the font options object.

    New in version 1.25.0: Only available with cairo 1.17.8+

  set_custom_palette_color(index: int, red: float, green: float, blue: float, alpha: float) → None
    Parameters:

      - index – the index of the color to set

      - red – red component of color

      - green – green component of color

      - blue – blue component of color

      - alpha – alpha component of color

    Sets a custom palette color for the font options object. This overrides the palette color at the specified color index. This override is independent of the selected palette index and will remain in place even if `FontOptions.set_color_palette()` is called to change the palette index.

    It is only possible to override color indexes already in the font palette.

    New in version 1.25.0: Only available with cairo 1.17.8+

  get_custom_palette_color(index: int) → Tuple[float, float, float, float]
    Parameters:

      index – the index of the color to get

    Returns:

      a (red, green, blue, alpha) tuple of float

    Raises:

      Error – if no custom color exists for the color index.

    Gets the custom palette color for the color index for the font options object.

    New in version 1.25.0: Only available with cairo 1.17.8+