Context#

class Context(**properties: Any)#

Superclasses: Object

A PangoContext stores global information used to control the itemization process.

The information stored by PangoContext includes the fontmap used to look up fonts, and default values such as the default language, default gravity, or default font.

To obtain a PangoContext, use create_context.

Constructors#

class Context
classmethod new() → Context#

Creates a new PangoContext initialized to default values.

This function is not particularly useful as it should always be followed by a set_font_map call, and the function create_context does these two steps together and hence users are recommended to use that.

If you are using Pango as part of a higher-level system, that system may have it’s own way of create a PangoContext. For instance, the GTK toolkit has, among others, gtk_widget_get_pango_context(). Use those instead.

Methods#

class Context
changed() → None#

Forces a change in the context, which will cause any PangoLayout using this context to re-layout.

This function is only useful when implementing a new backend for Pango, something applications won’t do. Backends should call this function if they have attached extra data to the context and such data is changed.

Added in version 1.32.4.

get_base_dir() → Direction#

Retrieves the base direction for the context.

See set_base_dir.

get_base_gravity() → Gravity#

Retrieves the base gravity for the context.

See set_base_gravity.

Added in version 1.16.

get_font_description() → FontDescription | None#

Retrieve the default font description for the context.

get_font_map() → FontMap | None#

Gets the PangoFontMap used to look up fonts for this context.

Added in version 1.6.

get_gravity() → Gravity#

Retrieves the gravity for the context.

This is similar to get_base_gravity, except for when the base gravity is AUTO for which get_for_matrix is used to return the gravity from the current context matrix.

Added in version 1.16.

get_gravity_hint() → GravityHint#

Retrieves the gravity hint for the context.

See set_gravity_hint for details.

Added in version 1.16.

get_language() → Language#

Retrieves the global language tag for the context.

get_matrix() → Matrix | None#

Gets the transformation matrix that will be applied when rendering with this context.

See set_matrix.

Added in version 1.6.

get_metrics(desc: FontDescription | None = None, language: Language | None = None) → FontMetrics#

Get overall metric information for a particular font description.

Since the metrics may be substantially different for different scripts, a language tag can be provided to indicate that the metrics should be retrieved that correspond to the script(s) used by that language.

The PangoFontDescription is interpreted in the same way as by itemize, and the family name may be a comma separated list of names. If characters from multiple of these families would be used to render the string, then the returned fonts would be a composite of the metrics for the fonts loaded for the individual families.

Parameters:

  • desc – a PangoFontDescription structure. None means that the font description from the context will be used.

  • language – language tag used to determine which script to get the metrics for. None means that the language tag from the context will be used. If no language tag is set on the context, metrics for the default language (as determined by get_default will be returned.

get_round_glyph_positions() → bool#

Returns whether font rendering with this context should round glyph positions and widths.

Added in version 1.44.

get_serial() → int#

Returns the current serial number of context.

The serial number is initialized to an small number larger than zero when a new context is created and is increased whenever the context is changed using any of the setter functions, or the PangoFontMap it uses to find fonts has changed. The serial may wrap, but will never have the value 0. Since it can wrap, never compare it with “less than”, always use “not equals”.

This can be used to automatically detect changes to a PangoContext, and is only useful when implementing objects that need update when their PangoContext changes, like PangoLayout.

Added in version 1.32.4.

list_families() → list[FontFamily]#

List all families for a context.

load_font(desc: FontDescription) → Font | None#

Loads the font in one of the fontmaps in the context that is the closest match for desc.

Parameters:

desc – a PangoFontDescription describing the font to load

load_fontset(desc: FontDescription, language: Language) → Fontset | None#

Load a set of fonts in the context that can be used to render a font matching desc.

Parameters:

  • desc – a PangoFontDescription describing the fonts to load

  • language – a PangoLanguage the fonts will be used for

set_base_dir(direction: Direction) → None#

Sets the base direction for the context.

The base direction is used in applying the Unicode bidirectional algorithm; if the direction is LTR or RTL, then the value will be used as the paragraph direction in the Unicode bidirectional algorithm. A value of WEAK_LTR or WEAK_RTL is used only for paragraphs that do not contain any strong characters themselves.

Parameters:

direction – the new base direction

set_base_gravity(gravity: Gravity) → None#

Sets the base gravity for the context.

The base gravity is used in laying vertical text out.

Added in version 1.16.

Parameters:

gravity – the new base gravity

set_font_description(desc: FontDescription | None = None) → None#

Set the default font description for the context

Parameters:

desc – the new pango font description

set_font_map(font_map: FontMap | None = None) → None#

Sets the font map to be searched when fonts are looked-up in this context.

This is only for internal use by Pango backends, a PangoContext obtained via one of the recommended methods should already have a suitable font map.

Parameters:

font_map – the PangoFontMap to set.

set_gravity_hint(hint: GravityHint) → None#

Sets the gravity hint for the context.

The gravity hint is used in laying vertical text out, and is only relevant if gravity of the context as returned by get_gravity is set to EAST or WEST.

Added in version 1.16.

Parameters:

hint – the new gravity hint

set_language(language: Language | None = None) → None#

Sets the global language tag for the context.

The default language for the locale of the running process can be found using get_default.

Parameters:

language – the new language tag.

set_matrix(matrix: Matrix | None = None) → None#

Sets the transformation matrix that will be applied when rendering with this context.

Note that reported metrics are in the user space coordinates before the application of the matrix, not device-space coordinates after the application of the matrix. So, they don’t scale with the matrix, though they may change slightly for different matrices, depending on how the text is fit to the pixel grid.

Added in version 1.6.

Parameters:

matrix – a PangoMatrix, or None to unset any existing matrix. (No matrix set is the same as setting the identity matrix.)

set_round_glyph_positions(round_positions: bool) → None#

Sets whether font rendering with this context should round glyph positions and widths to integral positions, in device units.

This is useful when the renderer can’t handle subpixel positioning of glyphs.

The default value is to round glyph positions, to remain compatible with previous Pango behavior.

Added in version 1.44.

Parameters:

round_positions – whether to round glyph positions