Font addons

al_destroy_font

void al_destroy_font(ALLEGRO_FONT *f)

Frees the memory being used by a font structure. This is now wholly handled in the vtable.

al_grab_font_from_bitmap

ALLEGRO_FONT *al_grab_font_from_bitmap(
   ALLEGRO_BITMAP *bmp,
   int ranges_n, int ranges[])

Work horse for grabbing a font from an Allegro bitmap.

Parameters:

  • bmp: The bitmap with the glyphs drawn onto it (TODO: describe expected format - opaque yellow background, fully transparent boxes all of same height but possibly variable width, white, possibly anti-aliased glyphs)
  • n: Number of unicode ranges in the bitmap.
  • ranges: 'n' pairs of first and last unicode point to map glyphs to for each range.

Examples:

int ranges[] = {32, 126};
al_font_grab_font_from_bitmap(bitmap, 1, ranges)

int ranges[] = {
    0x0020, 0x007F,  /* ASCII */
    0x00A1, 0x00FF,  /* Latin 1 */
    0x0100, 0x017F,  /* Extended-A */
    0x20AC, 0x20AC}; /* Euro */
al_font_grab_font_from_bitmap(bitmap, 4, ranges)

The first example will grab glyphs for the 95 standard printable ASCII characters, beginning with the space character (32) and ending with the tilde character (126). The second example will map the first 96 glyphs found in the bitmap to ASCII range, the next 95 glyphs to Latin 1, the next 128 glyphs to Extended-A, and the last glyph to the Euro character. (This is just the characters found in the Allegro 4 font.)

al_init_font_addon

void al_init_font_addon(void)

al_load_bitmap_font

ALLEGRO_FONT *al_load_bitmap_font(const char *fname)

al_load_font

ALLEGRO_FONT *al_load_font(char const *filename, int size, int flags)

Loads a font from disk.

al_load_bitmap_font

ALLEGRO_FONT *al_load_bitmap_font(const char *fname)

Import routine for the Allegro bitmap font format.

al_register_font_extension

bool al_register_font_extension(char const *extension,
   ALLEGRO_FONT *(*load_font)(char const *filename, int size, int flags))

Informs Allegro of a new font file type, telling it how to load files of this format.

al_get_font_line_height

int al_get_font_line_height(const ALLEGRO_FONT *f)

Returns the height of a character in the specified font.

al_get_text_width

int al_get_text_width(const ALLEGRO_FONT *f, const char *str)

Calculates the length of a string in a particular font.

al_get_ustr_width

int al_get_ustr_width(const ALLEGRO_FONT *f, ALLEGRO_USTR const *ustr)

See al_get_text_width.

al_draw_text

void al_draw_text(const ALLEGRO_FONT *font, float x, float y, int flags,
   char const *text)

Writes the 0-terminated string text onto bmp at position x, y, using the specified font.

The flags parameter can be 0 or one of the following flags:

  • ALLEGRO_ALIGN_LEFT - Draw the text left-aligned (same as 0).
  • ALLEGRO_ALIGN_CENTRE - Draw the text centered around the given position.
  • ALLEGRO_ALIGN_RIGHT - Draw the text right-aligned to the given position.

al_draw_ustr

void al_draw_ustr(const ALLEGRO_FONT *font, float x, float y, int flags,
   const ALLEGRO_USTR *ustr)

Like al_draw_text, except the text is passed as an ALLEGRO_USTR instead of a 0-terminated char array.

al_draw_justified_text

void al_draw_justified_text(const ALLEGRO_FONT *font, float x1, float x2,
   float y, float diff, int flags, const char *text)

Like al_draw_text, but justifies the string to the specified area.

al_draw_justified_ustr

void al_draw_justified_ustr(const ALLEGRO_FONT *font, float x1, float x2,
   float y, float diff, int flags, const ALLEGRO_USTR *ustr)

See al_draw_justified_text.

al_draw_textf

void al_draw_textf(const ALLEGRO_FONT *font, float x, float y, int flags,
   const char *format, ...)

Formatted text output, using a printf() style format string, all parameters have the same meaning as with al_draw_text otherwise.

al_draw_justified_textf

void al_draw_justified_textf(const ALLEGRO_FONT *f, float x1, float x2, float y,
   float diff, int flags, const char *format, ...)

Like al_draw_justified_text and al_draw_textf.

al_get_text_dimensions

void al_get_text_dimensions(const ALLEGRO_FONT *f,
   char const *text,
   int *bbx, int *bby, int *bbw, int *bbh, int *ascent, int *descent)

Sometimes, the al_get_text_width and al_get_font_line_height functions are not enough for exact text placement, so this function returns some additional information.

Returned variables (all in pixel):

  • x, y - Offset to upper left corner of bounding box.
  • w, h - Dimensions of bounding box.
  • ascent - Ascent of the font.
  • descent - Descent of the font.

If the X is the position you specify to draw text, the meaning of ascent and descent and the line height is like in the figure below. Note that glyphs may go to the left and upwards of the X, in which case x and y will have negative values.

X------------------------
    /\         |        |
   /  \        |        |
  /____\       ascent   |
 /      \      |        |
/        \     |        height
----------------        |
               |        |
               descent  |
               |        |
-------------------------

al_get_ustr_dimensions

void al_get_ustr_dimensions(const ALLEGRO_FONT *f,
   ALLEGRO_USTR const *ustr,
   int *bbx, int *bby, int *bbw, int *bbh, int *ascent, int *descent)

See al_get_text_dimensions.

al_load_ttf_font

ALLEGRO_FONT *al_load_ttf_font(char const *filename, int size, int flags)

Loads a truetype font from a file using the FreeType library. Quoting from the FreeType FAQ this means support for many different font formats:

TrueType, OpenType, Type1, CID, CFF, Windows FON/FNT, X11 PCF, and others

The size parameter determines the size the font will be rendered at, specified in pixel. The standard font size is measured in units per EM, if you instead want to specify the size as the total height of glyphs in pixel, pass it as a negative value.

Note: If you want to display text at multiple sizes, load the font multiple times with different size parameters.

The only flag supported right now is:

  • ALLEGRO_TTF_NO_KERNING - Do not use any kerning even if the font file supports it.

al_init_ttf_addon

bool al_init_ttf_addon(void)

Call this after al_init_font_addon to make al_load_font recognize .ttf and other formats supported by al_load_ttf_font.

Last updated: 2009-06-07 09:43:01 UTC