Pango Reference Manual: Rendering

## Rendering Rendering — Functions to run the rendering pipeline |

## Synopsis

                        PangoContext;
    struct              PangoItem;
    struct              PangoAnalysis;
    #define             PANGO_ANALYSIS_FLAG_CENTERED_BASELINE
    #define             PANGO_TYPE_DIRECTION

    GList *             pango_itemize                       (PangoContext *context,
                                                             const char *text,
                                                             int start_index,
                                                             int length,
                                                             PangoAttrList *attrs,
                                                             PangoAttrIterator *cached_iter);
    GList *             pango_itemize_with_base_dir         (PangoContext *context,
                                                             PangoDirection base_dir,
                                                             const char *text,
                                                             int start_index,
                                                             int length,
                                                             PangoAttrList *attrs,
                                                             PangoAttrIterator *cached_iter);
    void                pango_item_free                     (PangoItem *item);
    PangoItem *         pango_item_copy                     (PangoItem *item);
    PangoItem *         pango_item_new                      (void);
    PangoItem *         pango_item_split                    (PangoItem *orig,
                                                             int split_index,
                                                             int split_offset);
    GList *             pango_reorder_items                 (GList *logical_items);

    PangoContext *      pango_context_new                   (void);
    void                pango_context_changed               (PangoContext *context);
    guint               pango_context_get_serial            (PangoContext *context);
    void                pango_context_set_font_map          (PangoContext *context,
                                                             PangoFontMap *font_map);
    PangoFontMap *      pango_context_get_font_map          (PangoContext *context);
    PangoFontDescription * pango_context_get_font_description
                                                            (PangoContext *context);
    void                pango_context_set_font_description  (PangoContext *context,
                                                             const PangoFontDescription *desc);
    PangoLanguage *     pango_context_get_language          (PangoContext *context);
    void                pango_context_set_language          (PangoContext *context,
                                                             PangoLanguage *language);
    PangoDirection      pango_context_get_base_dir          (PangoContext *context);
    void                pango_context_set_base_dir          (PangoContext *context,
                                                             PangoDirection direction);
    PangoGravity        pango_context_get_base_gravity      (PangoContext *context);
    void                pango_context_set_base_gravity      (PangoContext *context,
                                                             PangoGravity gravity);
    PangoGravity        pango_context_get_gravity           (PangoContext *context);
    PangoGravityHint    pango_context_get_gravity_hint      (PangoContext *context);
    void                pango_context_set_gravity_hint      (PangoContext *context,
                                                             PangoGravityHint hint);
    const PangoMatrix * pango_context_get_matrix            (PangoContext *context);
    void                pango_context_set_matrix            (PangoContext *context,
                                                             const PangoMatrix *matrix);
    PangoFont *         pango_context_load_font             (PangoContext *context,
                                                             const PangoFontDescription *desc);
    PangoFontset *      pango_context_load_fontset          (PangoContext *context,
                                                             const PangoFontDescription *desc,
                                                             PangoLanguage *language);
    PangoFontMetrics *  pango_context_get_metrics           (PangoContext *context,
                                                             const PangoFontDescription *desc,
                                                             PangoLanguage *language);
    void                pango_context_list_families         (PangoContext *context,
                                                             PangoFontFamily ***families,
                                                             int *n_families);

    void                pango_break                         (const gchar *text,
                                                             int length,
                                                             PangoAnalysis *analysis,
                                                             PangoLogAttr *attrs,
                                                             int attrs_len);
    void                pango_get_log_attrs                 (const char *text,
                                                             int length,
                                                             int level,
                                                             PangoLanguage *language,
                                                             PangoLogAttr *log_attrs,
                                                             int attrs_len);
    void                pango_find_paragraph_boundary       (const gchar *text,
                                                             gint length,
                                                             gint *paragraph_delimiter_index,
                                                             gint *next_paragraph_start);
    void                pango_default_break                 (const gchar *text,
                                                             int length,
                                                             PangoAnalysis *analysis,
                                                             PangoLogAttr *attrs,
                                                             int attrs_len);
                        PangoLogAttr;

    void                pango_shape                         (const gchar *text,
                                                             gint length,
                                                             const PangoAnalysis *analysis,
                                                             PangoGlyphString *glyphs);
    void                pango_shape_full                    (const gchar *item_text,
                                                             gint item_length,
                                                             const gchar *paragraph_text,
                                                             gint paragraph_length,
                                                             const PangoAnalysis *analysis,
                                                             PangoGlyphString *glyphs);

## Object Hierarchy

      GObject
       +----PangoContext

      GBoxed
       +----PangoItem

## Description

The Pango rendering pipeline takes a string of Unicode characters and converts it into glyphs. The functions described in this section accomplish various steps of this process.

## Details

### PangoContext

    typedef struct _PangoContext PangoContext;

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

### struct PangoItem

    struct PangoItem {
      gint offset;
      gint length;
      gint num_chars;
      PangoAnalysis analysis;
    };

The PangoItem structure stores information abouta segment of text.

### struct PangoAnalysis

    struct PangoAnalysis {
      PangoEngineShape *shape_engine;
      PangoEngineLang  *lang_engine;
      PangoFont *font;

      guint8 level;
      guint8 gravity; /* PangoGravity */
      guint8 flags;

      guint8 script; /* PangoScript */
      PangoLanguage *language;

      GSList *extra_attrs;
    };

The PangoAnalysis structure stores information about the properties of a segment of text.

PangoEngineShape *`shape_engine`; | the engine for doing rendering-system-dependent processing.
PangoEngineLang *`lang_engine`; | the engine for doing rendering-system-independent processing.
PangoFont *`font`; | the font for this segment.
guint8 `level`; | the bidirectional level for this segment.
guint8 `gravity`; | the glyph orientation for this segment (A PangoGravity).
guint8 `flags`; | boolean flags for this segment (currently only one) (Since: 1.16).
guint8 `script`; | the detected script for this segment (A PangoScript) (Since: 1.18).
PangoLanguage *`language`; | the detected language for this segment.
GSList *`extra_attrs`; | extra attributes for this segment.

### PANGO_ANALYSIS_FLAG_CENTERED_BASELINE

    #define PANGO_ANALYSIS_FLAG_CENTERED_BASELINE (1 << 0)

Whether the segment should be shifted to center around the baseline. Used in vertical writing directions mostly.

Since 1.16

### PANGO_TYPE_DIRECTION

    #define PANGO_TYPE_DIRECTION (pango_direction_get_type ())

### pango_itemize ()

    GList *             pango_itemize                       (PangoContext *context,
                                                             const char *text,
                                                             int start_index,
                                                             int length,
                                                             PangoAttrList *attrs,
                                                             PangoAttrIterator *cached_iter);

Breaks a piece of text into segments with consistent directional level and shaping engine. Each byte of `text` will be contained in exactly one of the items in the returned list; the generated list of items will be in logical order (the start offsets of the items are ascending).

`cached_iter` should be an iterator over `attrs` currently positioned at a range before or containing `start_index`; `cached_iter` will be advanced to the range covering the position just after `start_index` + `length`. (i.e. if itemizing in a loop, just keep passing in the same `cached_iter`).

`context` : | a structure holding information that affects the itemization process.
`text` : | the text to itemize.
`start_index` : | first byte in `text` to process
`length` : | the number of bytes (not characters) to process after `start_index`. This must be >= 0.
`attrs` : | the set of attributes that apply to `text`.
`cached_iter` : | Cached attribute iterator, or `NULL`. [allow-none]
Returns : | a GList of PangoItem structures. The items should be freed using `pango_item_free()` probably in combination with `g_list_foreach()`, and the list itself using `g_list_free()`. [transfer full][element-type Pango.Item]

### pango_itemize_with_base_dir ()

    GList *             pango_itemize_with_base_dir         (PangoContext *context,
                                                             PangoDirection base_dir,
                                                             const char *text,
                                                             int start_index,
                                                             int length,
                                                             PangoAttrList *attrs,
                                                             PangoAttrIterator *cached_iter);

Like `pango_itemize()`, but the base direction to use when computing bidirectional levels (see `pango_context_set_base_dir()`), is specified explicitly rather than gotten from the PangoContext.

`context` : | a structure holding information that affects the itemization process.
`base_dir` : | base direction to use for bidirectional processing
`text` : | the text to itemize.
`start_index` : | first byte in `text` to process
`length` : | the number of bytes (not characters) to process after `start_index`. This must be >= 0.
`attrs` : | the set of attributes that apply to `text`.
`cached_iter` : | Cached attribute iterator, or `NULL`. [allow-none]
Returns : | a GList of PangoItem structures. The items should be freed using `pango_item_free()` probably in combination with `g_list_foreach()`, and the list itself using `g_list_free()`. [transfer full][element-type Pango.Item]

Since 1.4

### pango_item_free ()

    void                pango_item_free                     (PangoItem *item);

Free a PangoItem and all associated memory.

`item` : | a PangoItem, may be `NULL`

### pango_item_copy ()

    PangoItem *         pango_item_copy                     (PangoItem *item);

Copy an existing PangoItem structure.

`item` : | a PangoItem, may be `NULL`
Returns : | the newly allocated PangoItem, which should be freed with `pango_item_free()`, or `NULL` if `item` was NULL.

### pango_item_new ()

    PangoItem *         pango_item_new                      (void);

Creates a new PangoItem structure initialized to default values.

Returns : | the newly allocated PangoItem, which should be freed with `pango_item_free()`.

### pango_item_split ()

    PangoItem *         pango_item_split                    (PangoItem *orig,
                                                             int split_index,
                                                             int split_offset);

Modifies `orig` to cover only the text after `split_index`, and returns a new item that covers the text before `split_index` that used to be in `orig`. You can think of `split_index` as the length of the returned item. `split_index` may not be 0, and it may not be greater than or equal to the length of `orig` (that is, there must be at least one byte assigned to each item, you can't create a zero-length item). `split_offset` is the length of the first item in chars, and must be provided because the text used to generate the item isn't available, so `pango_item_split()` can't count the char length of the split items itself.

`orig` : | a PangoItem
`split_index` : | byte index of position to split item, relative to the start of the item
`split_offset` : | number of chars between start of `orig` and `split_index`
Returns : | new item representing text before `split_index`, which should be freed with `pango_item_free()`.

### pango_reorder_items ()

    GList *             pango_reorder_items                 (GList *logical_items);

From a list of items in logical order and the associated directional levels, produce a list in visual order. The original list is unmodified.

`logical_items` : | a GList of PangoItem in logical order. [element-type Pango.Item]
Returns : | a GList of PangoItem structures in visual order. (Please open a bug if you use this function. It is not a particularly convenient interface, and the code is duplicated elsewhere in Pango for that reason.). [transfer full][element-type Pango.Item]

### 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.

`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.

`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.

`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.

`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.

`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

`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.

`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()`.

`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()`.

`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.

`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()`.

`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.

`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.

`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.

`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`.

`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()`.

`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.

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.

`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_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`.

`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]

### 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`.

`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]

### 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.

`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.

`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]

### pango_break ()

    void                pango_break                         (const gchar *text,
                                                             int length,
                                                             PangoAnalysis *analysis,
                                                             PangoLogAttr *attrs,
                                                             int attrs_len);

Determines possible line, word, and character breaks for a string of Unicode text with a single analysis. For most purposes you may want to use `pango_get_log_attrs()`.

`text` : | the text to process
`length` : | length of `text` in bytes (may be -1 if `text` is nul-terminated)
`analysis` : | PangoAnalysis structure from `pango_itemize()`
`attrs` : | an array to store character information in. [array length=attrs_len]
`attrs_len` : | size of the array passed as `attrs`

### pango_get_log_attrs ()

    void                pango_get_log_attrs                 (const char *text,
                                                             int length,
                                                             int level,
                                                             PangoLanguage *language,
                                                             PangoLogAttr *log_attrs,
                                                             int attrs_len);

Computes a PangoLogAttr for each character in `text`. The `log_attrs` array must have one PangoLogAttr for each position in `text`; if `text` contains N characters, it has N+1 positions, including the last position at the end of the text. `text` should be an entire paragraph; logical attributes can't be computed without context (for example you need to see spaces on either side of a word to know the word is a word).

`text` : | text to process
`length` : | length in bytes of `text`
`level` : | embedding level, or -1 if unknown
`language` : | language tag
`log_attrs` : | array with one PangoLogAttr per character in `text`, plus one extra, to be filled in. [array length=attrs_len]
`attrs_len` : | length of `log_attrs` array

### pango_find_paragraph_boundary ()

    void                pango_find_paragraph_boundary       (const gchar *text,
                                                             gint length,
                                                             gint *paragraph_delimiter_index,
                                                             gint *next_paragraph_start);

Locates a paragraph boundary in `text`. A boundary is caused by delimiter characters, such as a newline, carriage return, carriage return-newline pair, or Unicode paragraph separator character. The index of the run of delimiters is returned in `paragraph_delimiter_index`. The index of the start of the paragraph (index after all delimiters) is stored in `next_paragraph_start`.

If no delimiters are found, both `paragraph_delimiter_index` and `next_paragraph_start` are filled with the length of `text` (an index one off the end).

`text` : | UTF-8 text
`length` : | length of `text` in bytes, or -1 if nul-terminated
`paragraph_delimiter_index` : | return location for index of delimiter. [out]
`next_paragraph_start` : | return location for start of next paragraph. [out]

### pango_default_break ()

    void                pango_default_break                 (const gchar *text,
                                                             int length,
                                                             PangoAnalysis *analysis,
                                                             PangoLogAttr *attrs,
                                                             int attrs_len);

This is the default break algorithm, used if no language engine overrides it. Normally you should use `pango_break()` instead. Unlike `pango_break()`, `analysis` can be `NULL`, but only do that if you know what you're doing. If you need an analysis to pass to `pango_break()`, you need to `pango_itemize()`. In most cases however you should simply use `pango_get_log_attrs()`.

`text` : | text to break
`length` : | length of text in bytes (may be -1 if `text` is nul-terminated)
`analysis` : | a PangoAnalysis for the `text`
`attrs` : | logical attributes to fill in
`attrs_len` : | size of the array passed as `attrs`

### PangoLogAttr

    typedef struct {
      guint is_line_break : 1;      /* Can break line in front of character */

      guint is_mandatory_break : 1; /* Must break line in front of character */

      guint is_char_break : 1;      /* Can break here when doing char wrap */

      guint is_white : 1;           /* Whitespace character */

      /* Cursor can appear in front of character (i.e. this is a grapheme
       * boundary, or the first character in the text).
       */
      guint is_cursor_position : 1;

      /* Note that in degenerate cases, you could have both start/end set on
       * some text, most likely for sentences (e.g. no space after a period, so
       * the next sentence starts right away).
       */

      guint is_word_start : 1;      /* first character in a word */
      guint is_word_end   : 1;      /* is first non-word char after a word */

      /* There are two ways to divide sentences. The first assigns all
       * intersentence whitespace/control/format chars to some sentence,
       * so all chars are in some sentence; is_sentence_boundary denotes
       * the boundaries there. The second way doesn't assign
       * between-sentence spaces, etc. to any sentence, so
       * is_sentence_start/is_sentence_end mark the boundaries of those
       * sentences.
       */
      guint is_sentence_boundary : 1;
      guint is_sentence_start : 1;  /* first character in a sentence */
      guint is_sentence_end : 1;    /* first non-sentence char after a sentence */

      /* If set, backspace deletes one character rather than
       * the entire grapheme cluster.
       */
      guint backspace_deletes_character : 1;

      /* Only few space variants (U+0020 and U+00A0) have variable
       * width during justification.
       */
      guint is_expandable_space : 1;

      /* Word boundary as defined by UAX#29 */
      guint is_word_boundary : 1; /* is NOT in the middle of a word */
    } PangoLogAttr;

The PangoLogAttr structure stores information about the attributes of a single character.

guint `is_line_break` : 1; | if set, can break line in front of character
guint `is_mandatory_break` : 1; | if set, must break line in front of character
guint `is_char_break` : 1; | if set, can break here when doing character wrapping
guint `is_white` : 1; | is whitespace character
guint `is_cursor_position` : 1; | if set, cursor can appear in front of character. i.e. this is a grapheme boundary, or the first character in the text. This flag implements Unicode's Grapheme Cluster Boundaries semantics.
guint `is_word_start` : 1; | is first character in a word
guint `is_word_end` : 1; | is first non-word char after a word Note that in degenerate cases, you could have both `is_word_start` and `is_word_end` set for some character.
guint `is_sentence_boundary` : 1; | is a sentence boundary. There are two ways to divide sentences. The first assigns all inter-sentence whitespace/control/format chars to some sentence, so all chars are in some sentence; `is_sentence_boundary` denotes the boundaries there. The second way doesn't assign between-sentence spaces, etc. to any sentence, so `is_sentence_start`/`is_sentence_end` mark the boundaries of those sentences.
guint `is_sentence_start` : 1; | is first character in a sentence
guint `is_sentence_end` : 1; | is first char after a sentence. Note that in degenerate cases, you could have both `is_sentence_start` and `is_sentence_end` set for some character. (e.g. no space after a period, so the next sentence starts right away)
guint `backspace_deletes_character` : 1; | if set, backspace deletes one character rather than the entire grapheme cluster. This field is only meaningful on grapheme boundaries (where `is_cursor_position` is set). In some languages, the full grapheme (e.g. letter + diacritics) is considered a unit, while in others, each decomposed character in the grapheme is a unit. In the default implementation of `pango_break()`, this bit is set on all grapheme boundaries except those following Latin, Cyrillic or Greek base characters.
guint `is_expandable_space` : 1; | is a whitespace character that can possibly be expanded for justification purposes. (Since: 1.18)
guint `is_word_boundary` : 1; | is a word boundary. More specifically, means that this is not a position in the middle of a word. For example, both sides of a punctuation mark are considered word boundaries. This flag is particularly useful when selecting text word-by-word. This flag implements Unicode's Word Boundaries semantics. (Since: 1.22)

### pango_shape ()

    void                pango_shape                         (const gchar *text,
                                                             gint length,
                                                             const PangoAnalysis *analysis,
                                                             PangoGlyphString *glyphs);

Given a segment of text and the corresponding PangoAnalysis structure returned from `pango_itemize()`, convert the characters into glyphs. You may also pass in only a substring of the item from `pango_itemize()`.

It is recommended that you use `pango_shape_full()` instead, since that API allows for shaping interaction happening across text item boundaries.

`text` : | the text to process
`length` : | the length (in bytes) of `text`
`analysis` : | PangoAnalysis structure from `pango_itemize()`
`glyphs` : | glyph string in which to store results

### pango_shape_full ()

    void                pango_shape_full                    (const gchar *item_text,
                                                             gint item_length,
                                                             const gchar *paragraph_text,
                                                             gint paragraph_length,
                                                             const PangoAnalysis *analysis,
                                                             PangoGlyphString *glyphs);

Given a segment of text and the corresponding PangoAnalysis structure returned from `pango_itemize()`, convert the characters into glyphs. You may also pass in only a substring of the item from `pango_itemize()`.

This is similar to `pango_shape()`, except it also can optionally take the full paragraph text as input, which will then be used to perform certain cross-item shaping interactions. If you have access to the broader text of which `item_text` is part of, provide the broader text as `paragraph_text`. If `paragraph_text` is `NULL`, item text is used instead.

`item_text` : | valid UTF-8 text to shape.
`item_length` : | the length (in bytes) of `item_text`. -1 means nul-terminated text.
`paragraph_text` : | (allow-none) text of the paragraph (see details). May be `NULL`.
`paragraph_length` : | the length (in bytes) of `paragraph_text`. -1 means nul-terminated text.
`analysis` : | PangoAnalysis structure from `pango_itemize()`.
`glyphs` : | glyph string in which to store results.

Since 1.32