DragonFly On-Line Manual Pages

ALLEGRO_VERTEX_ELEMENT(3)                            ALLEGRO_VERTEX_ELEMENT(3)

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:

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

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

       o 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(3), ALLEGRO_VERTEX_DECL(3), ALLEGRO_PRIM_ATTR(3),
       ALLEGRO_PRIM_STORAGE(3)

Allegro reference manual                             ALLEGRO_VERTEX_ELEMENT(3)