Contexts

Contexts — Global context object

Types and Values

Object Hierarchy

    GObject
    ╰── PangoContext

Description

The PangoContext structure stores global information influencing Pango's operation, such as the fontmap used to look up fonts, and default values such as the default language, default gravity, or default font.

Functions

pango_context_new ()

PangoContext *
pango_context_new (void);

Creates a new PangoContext initialized to default values.

This function is not particularly useful as it should always be followed by a pango_context_set_font_map() call, and the function pango_font_map_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, gdk_pango_context_get_for_screen(), and gtk_widget_get_pango_context(). Use those instead.

Returns

the newly allocated PangoContext, which should be freed with g_object_unref().


pango_context_changed ()

void
pango_context_changed (PangoContext *context);

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.

Parameters

context

a PangoContext

 

Since: 1.32.4


pango_context_get_serial ()

guint
pango_context_get_serial (PangoContext *context);

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.

Parameters

context

a PangoContext

 

Returns

The current serial number of context .

Since: 1.32.4


pango_context_set_font_map ()

void
pango_context_set_font_map (PangoContext *context,
                            PangoFontMap *font_map);

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

context

a PangoContext

 

font_map

the PangoFontMap to set.

 

pango_context_get_font_map ()

PangoFontMap *
pango_context_get_font_map (PangoContext *context);

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

Parameters

context

a PangoContext

 

Returns

the font map for the PangoContext. This value is owned by Pango and should not be unreferenced.

[transfer none]

Since: 1.6


pango_context_get_font_description ()

PangoFontDescription *
pango_context_get_font_description (PangoContext *context);

Retrieve the default font description for the context.

Parameters

context

a PangoContext

 

Returns

a pointer to the context's default font description. This value must not be modified or freed.

[transfer none]


pango_context_set_font_description ()

void
pango_context_set_font_description (PangoContext *context,
                                    const PangoFontDescription *desc);

Set the default font description for the context

Parameters

context

a PangoContext

 

desc

the new pango font description

 

pango_context_get_language ()

PangoLanguage *
pango_context_get_language (PangoContext *context);

Retrieves the global language tag for the context.

Parameters

context

a PangoContext

 

Returns

the global language tag.


pango_context_set_language ()

void
pango_context_set_language (PangoContext *context,
                            PangoLanguage *language);

Sets the global language tag for the context. The default language for the locale of the running process can be found using pango_language_get_default().

Parameters

context

a PangoContext

 

language

the new language tag.

 

pango_context_get_base_dir ()

PangoDirection
pango_context_get_base_dir (PangoContext *context);

Retrieves the base direction for the context. See pango_context_set_base_dir().

Parameters

context

a PangoContext

 

Returns

the base direction for the context.


pango_context_set_base_dir ()

void
pango_context_set_base_dir (PangoContext *context,
                            PangoDirection direction);

Sets the base direction for the context.

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

Parameters

context

a PangoContext

 

direction

the new base direction

 

pango_context_get_base_gravity ()

PangoGravity
pango_context_get_base_gravity (PangoContext *context);

Retrieves the base gravity for the context. See pango_context_set_base_gravity().

Parameters

context

a PangoContext

 

Returns

the base gravity for the context.

Since: 1.16


pango_context_set_base_gravity ()

void
pango_context_set_base_gravity (PangoContext *context,
                                PangoGravity gravity);

Sets the base gravity for the context.

The base gravity is used in laying vertical text out.

Parameters

context

a PangoContext

 

gravity

the new base gravity

 

Since: 1.16


pango_context_get_gravity ()

PangoGravity
pango_context_get_gravity (PangoContext *context);

Retrieves the gravity for the context. This is similar to pango_context_get_base_gravity(), except for when the base gravity is PANGO_GRAVITY_AUTO for which pango_gravity_get_for_matrix() is used to return the gravity from the current context matrix.

Parameters

context

a PangoContext

 

Returns

the resolved gravity for the context.

Since: 1.16


pango_context_get_gravity_hint ()

PangoGravityHint
pango_context_get_gravity_hint (PangoContext *context);

Retrieves the gravity hint for the context. See pango_context_set_gravity_hint() for details.

Parameters

context

a PangoContext

 

Returns

the gravity hint for the context.

Since: 1.16


pango_context_set_gravity_hint ()

void
pango_context_set_gravity_hint (PangoContext *context,
                                PangoGravityHint hint);

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 pango_context_get_gravity() is set PANGO_GRAVITY_EAST or PANGO_GRAVITY_WEST.

Parameters

context

a PangoContext

 

hint

the new gravity hint

 

Since: 1.16


pango_context_get_matrix ()

const PangoMatrix *
pango_context_get_matrix (PangoContext *context);

Gets the transformation matrix that will be applied when rendering with this context. See pango_context_set_matrix().

Parameters

context

a PangoContext

 

Returns

the matrix, or NULL if no matrix has been set (which is the same as the identity matrix). The returned matrix is owned by Pango and must not be modified or freed.

[nullable]

Since: 1.6


pango_context_set_matrix ()

void
pango_context_set_matrix (PangoContext *context,
                          const PangoMatrix *matrix);

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.

Parameters

context

a PangoContext

 

matrix

a PangoMatrix, or NULL to unset any existing matrix. (No matrix set is the same as setting the identity matrix.).

[allow-none]

Since: 1.6


pango_context_get_round_glyph_positions ()

gboolean
pango_context_get_round_glyph_positions
                               (PangoContext *context);

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

Parameters

context

a PangoContext

 

Since: 1.44


pango_context_set_round_glyph_positions ()

void
pango_context_set_round_glyph_positions
                               (PangoContext *context,
                                gboolean round_positions);

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.

Parameters

context

a PangoContext

 

round_positions

whether to round glyph positions

 

Since: 1.44


pango_context_load_font ()

PangoFont *
pango_context_load_font (PangoContext *context,
                         const PangoFontDescription *desc);

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

Parameters

context

a PangoContext

 

desc

a PangoFontDescription describing the font to load

 

Returns

the newly allocated PangoFont that was loaded, or NULL if no font matched.

[transfer full][nullable]


pango_context_load_fontset ()

PangoFontset *
pango_context_load_fontset (PangoContext *context,
                            const PangoFontDescription *desc,
                            PangoLanguage *language);

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

Parameters

context

a PangoContext

 

desc

a PangoFontDescription describing the fonts to load

 

language

a PangoLanguage the fonts will be used for

 

Returns

the newly allocated PangoFontset loaded, or NULL if no font matched.

[transfer full][nullable]


pango_context_get_metrics ()

PangoFontMetrics *
pango_context_get_metrics (PangoContext *context,
                           const PangoFontDescription *desc,
                           PangoLanguage *language);

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 pango_itemize(), and the family name may be a comma separated list of figures. 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

context

a PangoContext

 

desc

a PangoFontDescription structure. NULL means that the font description from the context will be used.

[allow-none]

language

language tag used to determine which script to get the metrics for. NULL 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 pango_language_get_default()) will be returned.

[allow-none]

Returns

a PangoFontMetrics object. The caller must call pango_font_metrics_unref() when finished using the object.


pango_context_list_families ()

void
pango_context_list_families (PangoContext *context,
                             PangoFontFamily ***families,
                             int *n_families);

List all families for a context.

Parameters

context

a PangoContext

 

families

location to store a pointer to an array of PangoFontFamily *. This array should be freed with g_free().

[out][array length=n_families][transfer container]

n_families

location to store the number of elements in descs .

[out]

Types and Values

PangoContext

typedef struct _PangoContext PangoContext;

The PangoContext structure stores global information used to control the itemization process.