Generated from asfont.h with ROBODoc v3.2.3 on Mon Feb 18 01:16:12 2002
DESCRIPTION
Text drawing functionality.
Text is drawn as an ASImage with only alpha channel. Since alpha
channel is 8 bit widths that allows for 256 shades to be used in
rendered glyphs. That in turn allows for smoothing and antialiasing
of the drawn text. Such an approcah allows for easy manipulation of
the drawn text, such as changing color, making it transparent,
texturizing, rotation, etc.
libAfterImage supports two types of fonts :
Fonts that could be rendered using standard Xlib functionality, and
fonts rendered by FreeType 2 library. That may include TrueType
fonts. When fonts are obtained via Xlib special processing is
performed in order to smooth its shape and leverage 256 shades
palette available.
Any font being used is has to be opened first. At that time its
properties are analysed and glyphs are cached in clients memory.
Special RLE compression method is used for font glyphs, significantly
reducing memory utilization without any effect on performance.
Font management and drawing functionality has been designed with
internatiolization in mind, althou support for locales is not
complete yet.
SEE ALSO
Structures :
ASFontManager
ASFont
ASGlyph
ASGlyphRange
Functions :
create_font_manager(), destroy_font_manager(),
open_freetype_font(), open_X11_font(), get_asfont(),
destroy_font(), print_asfont(), print_asglyph(),
draw_text(),
get_asfont_glyph_spacing(), set_asfont_glyph_spacing()
Other libAfterImage modules :
ascmap.h asfont.h asimage.h asvisual.h blender.h export.h
import.h transform.h ximage.h
AUTHOR
Sasha Vasko <sasha at aftercode dot net>
FUNCTION
Max value of glyphs per font allowed. We need that so we can detect
and avoid broken fonts somehow.
SOURCE
#define MAX_GLYPHS_PER_FONT 2048
FUNCTION
Supported types of fonts - Xlib or FreeType 2
ASF_GuessWho will enable autodetection of the font type.
It is attempted to be opened as FreeType font first, and if that
fails - it will be opened as Xlib font.
SOURCE
typedef enum
{
ASF_X11 = 0,
ASF_Freetype,
ASF_GuessWho
}ASFontType;
FUNCTION
Convinient macro so we can transparently determine the number of
bytes that character spans. It assumes UTF-8 encoding when I18N is
enabled.
SOURCE
#ifdef I18N
/* size of the UTF-8 encoded character is based on value of the first byte : */
#define CHAR_SIZE(c) (((c)&0x80)?(((c)&0x40)?(((c)&0x20)?(((c)&0x10)?5:4):3):2):1)
#else
#define CHAR_SIZE(c) 1
#endif
NAME
ASGlyph
DESCRIPTION
Stores glyph's image, as well as width, height and other
characteristics of the glyph.
SOURCE
typedef struct ASGlyph
{
CARD8 *pixmap ; /* glyph's RLE encoded pixmap */
unsigned short width, height ; /* meaningfull width and height
* of the glyphs pixmap */
short lead, step ; /* distance pen position to glyph
* beginning and to the next glyph */
short ascend, descend ; /* distance of the top of the
* glyph from the baseline */
}ASGlyph;
NAME
ASGlyphRange
DESCRIPTION
Organizes glyphs that belongs to the continuos range of char codes.
ASGlyphRange structures could be tied together to cover entire
codeset supported by the font.
SOURCE
typedef struct ASGlyphRange
{
unsigned long min_char, max_char; /* Code range.
* for some locales that would
* be sufficient to simply set
* range of characteres
* supported by font */
ASGlyph *glyphs; /* array of glyphs belonging to
* that code range */
struct ASGlyphRange *below, *above;
}ASGlyphRange;
NAME
ASFont
DESCRIPTION
Structure to contain all the font characteristics, as well as
set of glyph images. Such structure has to be created/opened prior to
being able to draw characters with any font.
SOURCE
typedef struct ASFont
{
unsigned long magic ;
int ref_count ;
struct ASFontManager *fontman; /* our owner */
char *name;
ASFontType type ;
ASGlyphRange *codemap; /* linked list of glyphsets, each
* representing continuos range of
* available codes */
ASGlyph default_glyph; /* valid glyph to be drawn when
* code is not valid */
unsigned int max_height, /* maximiu height of the character
* glyph */
max_ascend, /* maximum distance from the baseline
* to the top of the character glyph */
space_size; /* fixed width value to be used when
* rendering spaces and tabs */
int spacing_x, spacing_y;
#define LEFT_TO_RIGHT 1
#define RIGHT_TO_LEFT -1
int pen_move_dir ; /* direction of the text flow */
#ifdef HAVE_FREETYPE
FT_Face ft_face; /* free type font handle */
#else
CARD32 *pad;
#endif
}ASFont;
NAME
ASFontManager
DESCRIPTION
Global data identifying connection to external libraries, as well as
fonts location paths.
This structure has to be created/initialized prior to any font being
loaded.
It also holds list of fonts that are currently open, allowing for
easy access to fonts.
When ASFontManagaer object is destroyd it automagically closes all
the open fonts.
SOURCE
typedef struct ASFontManager
{
Display *dpy;
char *font_path ;
ASHashTable *fonts_hash ;
size_t unicode_used;
CARD32 *local_unicode; /* list of unicodes from current locale
* - we use it to limit number of glyphs
* we load */
Bool ft_ok ;
#ifdef HAVE_FREETYPE
FT_Library ft_library; /* free type library handle */
#else
void *pad ;
#endif
}ASFontManager;
FUNCTION
Available types of 3D text to be drawn.
SOURCE
typedef enum ASText3DType{
AST_Plain =0, /* regular 2D text */
AST_Embossed,
AST_Sunken,
AST_ShadeAbove,
AST_ShadeBelow,
AST_EmbossedThick,
AST_SunkenThick,
AST_3DTypes
}ASText3DType;
SYNOPSIS
ASFontManager *create_font_manager( Display *dpy,
const char *font_path,
ASFontManager *reusable_memory );
INPUTS
dpy - pointer to valid and opened Display.
font_path - string, representing colon separated list of
directories to search for FreeType fonts.
reusable_memory - optional preallocated memory for the ASFontMagaer
object
RETURN VALUE
Pointer to Initialized ASFontManager object on success.
NULL otherwise.
DESCRIPTION
create_font_manager() will create new ASFontManager structure if
needed. It wioll then store copy of font_path and supplied pointer to
Display in it. At that time Hash table of loaded fonts is initialized,
and if needed FreeType library is initialized as well.
ASFontManager object returned by this functions has to be open at all
times untill text drawing is no longer needed.
SYNOPSIS
void destroy_font_manager( ASFontManager *fontman,
Bool reusable );
INPUTS
fontman - pointer to valid ASFontManager object to be deallocated.
reusable - If True, then memory holding object itself will not be
freed - only resources will be deallocated. That is
usefull for structures created on stack.
DESCRIPTION
destroy_font_manager() closes all the fonts open with this
ASFontManager. It will also close connection to FreeType library, and
deallocate all cached data. If reusable is False - then memory used
for object itself will not be freed.
SYNOPSIS
ASFont *open_freetype_font( ASFontManager *fontman,
const char *font_string,
int face_no,
int size, Bool verbose);
INPUTS
fontman - pointer to previously created ASFontManager. Needed for
connection to FreeType library, as well as path to
search fonts in.
font_string - filename of the file containing font's data.
face_no - number of face within the font file
size - font size in points. Applicable only to scalable fonts,
such as TrueType.
verbose - if True, extensive error messages will be printed if
problems encountered.
RETURN VALUE
pointer to Opened ASFont structure, containing all the glyphs of the
font, as well as other relevant info. On failure returns NULL.
DESCRIPTION
open_freetype_font() will attempt to find font file in any of the
directories specified in ASFontManager's font_path. If it fails to do
so - then it will check if filename has alldigit extentions. It will
then try to interpret that extention as a face number, and try and
find the file with extention stripped off.
If file was found function will atempt to read it using FreeType
library. If requested face is not available in the font - face 0 will
be used.
On success all the font's glyphs will be rendered and cached, and
needed font geometry info collected.
When FreeType Library is not available that function does nothing.
SYNOPSIS
ASFont *open_X11_font( ASFontManager *fontman,
const char *font_string);
INPUTS
fontman - pointer to previously created ASFontManager. Needed for
connection X Server.
font_string - name of the font as recognized by Xlib.
RETURN VALUE
pointer to Opened ASFont structure, containing all the glyphs of the
font, as well as other relevant info. On failure returns NULL.
DESCRIPTION
open_X11_font() attempts to load and query font using Xlib calls.
On success it goes thgroughthe codemap of the font and renders all
the glyphs available. Glyphs then gets transfered to the client's
memory and encoded using RLE compression. At this time smoothing
filters are applied on glyph pixmaps, if its size exceeds threshold.
TODO
implement proper XFontSet support, when used with I18N enabled.
SYNOPSIS
ASFont *get_asfont( ASFontManager *fontman,
const char *font_string,
int face_no, int size,
ASFontType type );
INPUTS
fontman - pointer to previously created ASFontManager. Needed for
connection to FreeType library, path to search fonts
in, and X Server connection.
font_string - font name or filename of the file containing font's data.
face_no - number of face within the font file
size - font size in points. Applicable only to scalable fonts,
such as TrueType.
type - specifies the type of the font, or GuessWho for
autodetection.
RETURN VALUE
pointer to Opened ASFont structure, containing all the glyphs of the
font, as well as other relevant info. On failure returns NULL.
DESCRIPTION
This function provides unified interface to font loading. It performs
search in ASFontManager's list to see if this specific font has been
loaded already, and if so - returns pointer to relevant structure.
Otherwise it tryes to load font as FreeType font first, and then
Xlib font, unless exact font type is specifyed.
SYNOPSIS
void release_font( ASFont *font );
INPUTS
font - pointer to the valid ASFont structure containing loaded font.
RETURN VALUE
returns current reference count. -1 means that object has been
destroyed.
DESCRIPTION
This function will decrement reference count on loaded font and if
reference count will be less then 0 ( meaning that release_font() has
been called more times then get_asfont() ) it will close the font,
remove it from ASFontManager's list, destroy all the glyphs and
generally free everything else used by ASFont.
Otherwise font will remain in memory for faster reuse.
SYNOPSIS
void print_asfont( FILE* stream,
ASFont* font);
INPUTS
stream - output file pointer
font - pointer to ASFont structure to print.
DESCRIPTION
prints all the geometry information about font.
SYNOPSIS
void print_asglyph( FILE* stream,
ASFont* font, unsigned long c);
INPUTS
stream - output file pointer
font - pointer to ASFont structure to print.
c - character code to print glyph for
DESCRIPTION
prints out contents of the cached glyph for specifyed character code.
SYNOPSIS
ASImage *draw_text( const char *text,
ASFont *font, ASText3DType type,
int compression );
Bool get_text_size( const char *text,
ASFont *font, ASText3DType type,
unsigned int *width, unsigned int *height );
INPUTS
text - actuall text to render
font - pointer to ASFont to render text with
type - one of the few available types of 3D text.
compression - compression level to attempt on resulting ASImage.
width - pointer to value to be set to text width.
height - pointer to value to be set to text height.
RETURN VALUE
Pointer to new ASImage containing rendered text on success.
NULL on failure.
DESCRIPTION
draw_text() creates new ASImage of the size big enough to contain
entire text. It then renders the text using supplied font as an alpha
channel of ASImage.
get_text_size() can be used to determine the size of the text about
to be drawn, so that appropriate drawable can be prepared.
SYNOPSIS
Bool get_asfont_glyph_spacing( ASFont* font, int *x, int *y );
INPUTS
font - Loaded ASFont structure.
x - pointer to the variable to receive horizontal spacing value.
y - pointer to the variable to receive vertical spacing value.
RETURN VALUE
True if meaningfull information has been returned.
DESCRIPTION
Returns inter-glyph spacing of specified font.
SYNOPSIS
Bool set_asfont_glyph_spacing( ASFont* font, int x, int y );
INPUTS
font - Loaded ASFont structure.
x - new horizontal spacing value.
y - new vertical spacing value.
RETURN VALUE
TRue on success.
DESCRIPTION
Changes inter-glyph spacing of the specified font.