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# ASFont

text 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 useful 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 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()

- 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_asfont()

- NAME

  print_asfont()

- 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.

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.

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