Glyph Storage

PANGO_SCALE

#define PANGO_SCALE 1024

The PANGO_SCALE macro represents the scale between dimensions used for pango distances and device units. (The definition of device units is dependent on the output device; it will typically be pixels for a screen, and points for a printer.) PANGO_SCALE is currently 1000, but this may be changed in the future.

PANGO_PIXELS()

#define     PANGO_PIXELS(d)

struct PangoRectangle

struct PangoRectangle
{
  int x;
  int y;
  int width;
  int height;
};

The PangoRectangle structure represents a rectangle. It is frequently used to represent the logical or ink extents of a single glyph or section of text. (See, for instance, pango_font_get_glyph_extents())

PANGO_ASCENT()

#define PANGO_ASCENT(rect) (-(rect).y)

Extracts the ascent from a PangoRectangle representing glyph extents. The ascent is the distance from the baseline to the highest point of the character. This is positive if the glyph ascends above the baseline.

PANGO_DESCENT()

#define PANGO_DESCENT(rect) ((rect).y + (rect).height)

Extracts the descent from a PangoRectangle representing glyph extents. The descent is the distance from the baseline to the lowest point of the character. This is positive if the glyph descends below the baseline.

PANGO_LBEARING()

#define PANGO_LBEARING(rect) ((rect).x)

Extracts the left bearing from a PangoRectangle representing glyph extents. The descent is the distance from the horizontal origin to the farthest left point of the character. This is positive for characters drawn completely to the right of the glyph origin.

PANGO_RBEARING()

#define PANGO_RBEARING(rect) ((rect).x + (rect).width)

Extracts the left bearing from a PangoRectangle representing glyph extents. The descent is the distance from the horizontal origin to the farthest left point of the character. This is positive except for characters drawn completely to the left of the horizontal origin.

PangoGlyph

typedef guint32 PangoGlyph;

The PangoGlyph structure represents a single glyph in the output form of a string. It contains the following fields.

struct PangoGlyphInfo

struct PangoGlyphInfo
{
  PangoGlyph    glyph;
  PangoGlyphGeometry geometry;
  PangoGlyphVisAttr  attr;
};

struct PangoGlyphGeometry

struct PangoGlyphGeometry
{
  PangoGlyphUnit width;
  PangoGlyphUnit x_offset;  
  PangoGlyphUnit y_offset;
};

The PangoGlyphGeometry structure contains width and positioning information for a single glyph. Distances are in 1/64ths of a point.

PangoGlyphUnit

typedef gint32 PangoGlyphUnit;

The PangoGlyphUnit type is used to store dimensions within Pango. Dimensions are stored in 1/64ths of a point.

struct PangoGlyphVisAttr

struct PangoGlyphVisAttr
{
  guint is_cluster_start : 1;
};

The PangoGlyphVisAttr is used to communicate information between the shaping phase and the rendering phase. It's contents are still evolving.

struct PangoGlyphString

struct PangoGlyphString {
  gint num_glyphs;

  PangoGlyphInfo *glyphs;

  /* This is a memory inefficient way of representing the
   * information here - each value gives the character index
   * of the start of the cluster to which the glyph belongs.
   */
  gint *log_clusters;

  /*< private >*/
  gint space;
};

The PangoGlyphString structure is used to store strings of glyphs with geometry and visual attribute information. The storage for the glyph information is owned by the structure which simplifies memory management.

PangoGlyphString contains the following publically accessible fields

pango_glyph_string_new ()

PangoGlyphString* pango_glyph_string_new    (void);

Create a new PangoGlyphString.

pango_glyph_string_set_size ()

void        pango_glyph_string_set_size     (PangoGlyphString *string,
                                             gint new_len);

Resize a glyph string to the given length.

pango_glyph_string_free ()

void        pango_glyph_string_free         (PangoGlyphString *string);

Free a glyph string and associated storage.

pango_glyph_string_extents ()

void        pango_glyph_string_extents      (PangoGlyphString *glyphs,
                                             PangoFont *font,
                                             PangoRectangle *ink_rect,
                                             PangoRectangle *logical_rect);

Compute the logical and ink extents of a glyph string. See the documentation for pango_font_get_glyph_extents() for details about the interpretation of the rectangles.

pango_glyph_string_index_to_x ()

void        pango_glyph_string_index_to_x   (PangoGlyphString *glyphs,
                                             char *text,
                                             int length,
                                             PangoAnalysis *analysis,
                                             int index,
                                             gboolean trailing,
                                             int *x_pos);

Converts from character position to x position. (X position is measured from the left edge of the run)

pango_glyph_string_x_to_index ()

void        pango_glyph_string_x_to_index   (PangoGlyphString *glyphs,
                                             char *text,
                                             int length,
                                             PangoAnalysis *analysis,
                                             int x_pos,
                                             int *index,
                                             int *trailing);

Convert from x offset to position.

pango_glyph_string_get_logical_widths ()

void        pango_glyph_string_get_logical_widths
                                            (PangoGlyphString *glyphs,
                                             const char *text,
                                             int length,
                                             int embedding_level,
                                             int *logical_widths);

Given a PangoGlyphString resulting from pango_shape() and the corresponding text, determine the screen width corresponding to each character. When multiple characters compose a single cluster, the width of the entire cluster is divided equally among the characters.