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ASFonttext drawing functionality and handling of TTF and X11 fonts

    libAfterImage/asfont.h
  • NAME
    asfont

  • 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>
    libAfterImage/MAX_GLYPHS_PER_FONT
  • NAME
    MAX_GLYPHS_PER_FONT

    - 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

    libAfterImage/ASFontType
  • NAME
    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.

  • SOURCE

    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
  • 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 */
    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 */
                                    /* 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
    • 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 ;

    libAfterImage/ASFont
  • 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 ;
    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
    • 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 ;

    libAfterImage/ASText3DType
  • NAME
    ASText3DType

    - 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_OutlineAbove,
    AST_OutlineBelow,
    AST_OutlineFull,
    AST_3DTypes
} ASText3DType ;

    libAfterImage/ASTextAttributes
  • NAME
    ASTextAttributes

    - Attributes for  text rendering

  • SOURCE

    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()
  • NAME
    create_font_manager()

  • 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.
    libAfterImage/asfont/destroy_font_manager()
  • NAME
    destroy_font_manager()

  • 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.
    libAfterImage/asfont/open_freetype_font()
  • NAME
    open_freetype_font()

  • 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.
    libAfterImage/asfont/open_X11_font()
  • NAME
    open_X11_font()

  • 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.
    libAfterImage/asfont/get_asfont()
  • NAME
    get_asfont()

  • 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.
    libAfterImage/asfont/release_font()
  • NAME
    release_font()

  • 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.
    libAfterImage/asfont/print_asglyph()
  • NAME
    print_asglyph()

  • 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.
    libAfterImage/asfont/draw_text()
  • NAME
    draw_text()

    draw_fancy_text()

    get_text_size()

    get_fancy_text_size();

  • SYNOPSIS
     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 );
  • 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.
    libAfterImage/asfont/get_asfont_glyph_spacing()
  • NAME
    get_asfont_glyph_spacing()

  • 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.
    libAfterImage/asfont/set_asfont_glyph_spacing()
  • NAME
    set_asfont_glyph_spacing()

  • 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.

AfterStep Documentation   -   October 2005     ( 80% complete )
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