NAME

       ALLEGRO_VERTEX_ELEMENT - Allegro 5 API

SYNOPSIS

              #include <allegro5/allegro_primitives.h>

              typedef struct ALLEGRO_VERTEX_ELEMENT ALLEGRO_VERTEX_ELEMENT;

DESCRIPTION

       A  small  structure  describing  a certain element of a vertex.  E.g.  the position of the
       vertex, or its color.  These structures are used by the al_create_vertex_decl function  to
       create  the  vertex  declaration.   For  that  they generally occur in an array.  The last
       element of such an array should have the attribute field equal to 0, to signify that it is
       the  end of the array.  Here is an example code that would create a declaration describing
       the ALLEGRO_VERTEX structure (passing this as vertex declaration to al_draw_prim would  be
       identical to passing NULL):

              /* On compilers without the offsetof keyword you need to obtain the
               * offset with sizeof and make sure to account for packing.
               */
              ALLEGRO_VERTEX_ELEMENT elems[] = {
                 {ALLEGRO_PRIM_POSITION, ALLEGRO_PRIM_FLOAT_3, offsetof(ALLEGRO_VERTEX, x)},
                 {ALLEGRO_PRIM_TEX_COORD_PIXEL, ALLEGRO_PRIM_FLOAT_2, offsetof(ALLEGRO_VERTEX, u)},
                 {ALLEGRO_PRIM_COLOR_ATTR, 0, offsetof(ALLEGRO_VERTEX, color)},
                 {0, 0, 0}
              };
              ALLEGRO_VERTEX_DECL* decl = al_create_vertex_decl(elems, sizeof(ALLEGRO_VERTEX));

       Fields:

       • attribute - A member of the ALLEGRO_PRIM_ATTR(3alleg5) enumeration, specifying what this
         attribute signifies

       • storage - A member of the ALLEGRO_PRIM_STORAGE(3alleg5) enumeration, specifying how this
         attribute is stored

       • offset  - Offset in bytes from the beginning of the custom vertex structure.  C function
         offsetof is very useful here.

SEE ALSO

       al_create_vertex_decl(3alleg5), ALLEGRO_VERTEX_DECL(3alleg5),  ALLEGRO_PRIM_ATTR(3alleg5),
       ALLEGRO_PRIM_STORAGE(3alleg5)