bionic (3) ALLEGRO_VERTEX_ELEMENT.3alleg5.gz

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(3alleg5) 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(3alleg5) 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.  The 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)