| asfont(3x) | AfterStep X11 window manager | asfont(3x) |
asfont - text drawing functionality and handling of TTF and X11 fonts libAfterImage/asfont.h
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.
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
Sasha Vasko <sasha at aftercode dot net>
libAfterImage/MAX_GLYPHS_PER_FONT
- Max value of glyphs per font allowed. We need that so we can detect and avoid broken fonts somehow.
#define MAX_GLYPHS_PER_FONT 2048
libAfterImage/ASFontType
- 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.
typedef enum {
ASF_X11 = 0,
ASF_Freetype = (0x01<<0),
ASF_GuessWho = (0x01<<1), #define ASF_TypeMask
(ASF_GuessWho|ASF_Freetype)
/* flags below should be combined with one of the above values */
ASF_Monospaced = (0x01<<2),
ASF_RightToLeft = (0x01<<3), /* direction of the text flow */
ASF_HasKerning = (0x01<<4) }ASFontType;
libAfterImage/ASGlyph
Stores glyph's image, as well as width, height and other
characteristics of the glyph.
typedef struct ASGlyph {
CARD8 *pixmap ; /* glyph's RLE encoded pixmap */
short width, height ; /* meaningful width and height
* of the glyphs pixmap */
short lead, step ; /* distance pen position to glyph
* beginning and to the next glyph */
/* in XRender it should be used as so:
* x = -lead, xOff = step
*/
short ascend, descend ; /* distance of the top of the
* glyph from the baseline */
/* in XRender it should be used as so:
* y = -ascend, yOff = 0
*/
unsigned int font_gid ; /* index of the glyph inside the font( TTF only ) */
long xrender_gid ; /* Used only with XRender - gid of the glyph in GlyphSet
*/ }ASGlyph;
libAfterImage/ASGlyphRange
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.
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;
libAfterImage/ASFont
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.
typedef struct ASFont {
unsigned long magic ;
int ref_count ;
struct ASFontManager *fontman; /* our owner */
char *name;
ASFontType type ;
ASFlagType flags ;
ASGlyphRange *codemap; /* linked list of glyphsets, each
* representing continuos range of
* available codes - used for ASCII
* codes */
ASHashTable *locale_glyphs; /* hash of locale specific glyphs */
ASGlyph default_glyph; /* valid glyph to be drawn when
* code is not valid */
int max_height; /* maximiu height of the character
* glyph */
int max_ascend, /* maximum distance from the baseline
* to the top of the character glyph */
max_descend; /* need both descend and ascend to be
able to dynamically recalculate font
height while adding new characters */
int space_size; /* fixed width value to be used when
* rendering spaces and tabs */
int spacing_x, spacing_y;
/* If these are set to anything above 0 then all the glyphs has to be
* padded ( if its smaller then the cell ) or scaled down
* ( if its bigger then the cell )
*/
int cell_width, cell_height ;
#ifdef HAVE_FREETYPE
FT_Face ft_face; /* free type font handle */ #else
CARD32 *pad; #endif
unsigned long xrender_glyphset ; /* GlyphSet is the actuall datatype,
* but for easier compilation -
* we use generic which is the same */ }ASFont;
libAfterImage/ASFontManager
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.
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;
libAfterImage/ASText3DType
- Available types of 3D text to be drawn.
typedef enum ASText3DType{
AST_Plain =0, /* regular 2D text */
AST_Embossed,
AST_Sunken,
AST_ShadeAbove,
AST_ShadeBelow,
AST_EmbossedThick,
AST_SunkenThick,
AST_OutlineAbove,
AST_OutlineBelow,
AST_OutlineFull,
AST_3DTypes }ASText3DType;
libAfterImage/ASTextAttributes
- Attributes for text rendering
typedef struct ASTextAttributes { #define ASTA_UseTabStops (0x01<<0)
unsigned int version ;
/* structure version, so we can implement future
* extensions without breaking binary apps */
ASFlagType rendition_flags ;
ASText3DType type;
ASCharType char_type;
unsigned int tab_size ; /* tab size in chars - defaults to 8 */
unsigned int origin ; /* distance from the left margin
* (in pixels) */
unsigned int *tab_stops ; /* tab stops in pixels where
* left margin is 0 */
unsigned int tab_stops_num ;
ARGB32 fore_color ; /* used with 3D type of Outlined */
unsigned int width; #define ASTA_VERSION_1 1
#define ASTA_VERSION_INTERNAL ASTA_VERSION_1 }ASTextAttributes;
libAfterImage/asfont/create_font_manager()
ASFontManager *create_font_manager( Display *dpy,
const char *font_path,
ASFontManager *reusable_memory );
Pointer to Initialized ASFontManager object on success. NULL
otherwise.
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 until text drawing is
no longer needed.
libAfterImage/asfont/destroy_font_manager()
void destroy_font_manager( ASFontManager *fontman,
Bool reusable );
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.
libAfterImage/asfont/open_freetype_font()
ASFont *open_freetype_font( ASFontManager *fontman,
const char *font_string,
int face_no,
int size, Bool verbose);
pointer to Opened ASFont structure, containing all the glyphs of
the font, as well as other relevant info. On failure returns NULL.
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 extensions. It will then try to
interpret that extension as a face number, and try and find the file with
extension 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.
libAfterImage/asfont/open_X11_font()
ASFont *open_X11_font( ASFontManager *fontman,
const char *font_string);
pointer to Opened ASFont structure, containing all the glyphs of
the font, as well as other relevant info. On failure returns NULL.
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 transferred 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.
implement proper XFontSet support, when used with I18N enabled.
libAfterImage/asfont/get_asfont()
ASFont *get_asfont( ASFontManager *fontman,
const char *font_string,
int face_no, int size,
ASFontType type );
pointer to Opened ASFont structure, containing all the glyphs of
the font, as well as other relevant info. On failure returns NULL.
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.
libAfterImage/asfont/release_font()
void release_font( ASFont *font );
returns current reference count. -1 means that object has been
destroyed.
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.
libAfterImage/asfont/print_asfont()
void print_asfont( FILE* stream,
ASFont* font);
prints all the geometry information about font.
libAfterImage/asfont/print_asglyph()
void print_asglyph( FILE* stream,
ASFont* font, unsigned long c);
prints out contents of the cached glyph for specifyed character
code.
libAfterImage/asfont/draw_text()
draw_fancy_text()
get_text_size()
get_fancy_text_size();
ASImage *draw_text( const char *text,
ASFont *font, ASText3DType type,
int compression ); ASImage *draw_fancy_text( const void *text,
struct ASFont *font, ASTextAttributes *attr,
int compression,
int length ); Bool get_text_size( const char *text,
ASFont *font, ASText3DType type,
unsigned int *width, unsigned int *height ); Bool get_fancy_text_size( const
void *text,
struct ASFont *font, ASTextAttributes *attr,
unsigned int *width, unsigned int *height,
int length,
int *x_positions );
Pointer to new ASImage containing rendered text on success. NULL
on failure.
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.
libAfterImage/asfont/get_asfont_glyph_spacing()
Bool get_asfont_glyph_spacing( ASFont* font, int *x, int *y );
True if meaningful information has been returned.
Returns inter-glyph spacing of specified font.
libAfterImage/asfont/set_asfont_glyph_spacing()
Bool set_asfont_glyph_spacing( ASFont* font, int x, int y );
TRue on success.
Changes inter-glyph spacing of the specified font.
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