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PgDrawSpan(), PgDrawSpanv(), PgDrawSpanCx(), PgDrawSpanCxv()

Draw a list of spans


int PgDrawSpan( PgSpan_t const *ptr,
                int num,
                PhPoint_t const *pos,
                int flags );

int PgDrawSpanv( PgSpan_t const *ptr,
                 int num,
                 PhPoint_t const *pos,
                 int flags );

int PgDrawSpanCx( void *dc,
                  PgSpan_t const *ptr,
                  int num,
                  PhPoint_t const *pos,
                  int flags );

int PgDrawSpanCxv( void *dc,
                   PgSpan_t const *ptr,
                   int num,
                   PhPoint_t const *pos,
                   int flags );




These low-level draw primitives let you render complex shapes not supported by the Photon graphics drivers.

The functions draw a list of spans. The spans are defined as a list of PgSpan_t records. Here are the members of PgSpan_t:

short x1
starting x position
short x2
last x position
short y
y position

The number of spans is defined by the num parameter. The location of the spans is offset by the pos parameter.

You can set flags to one of the following:

Note: If you call the “v” forms of this function, the data isn't physically copied into the draw buffer. Instead, a pointer to the list of spans is stored until the draw buffer is flushed. Make sure you call PgFlush() or PgFlushCx() before you modify the list.

PgDrawSpan() and PgDrawSpanv() work on the current draw context, while you can specify the draw context dc for PgDrawSpanCx() and PgDrawSpanCxv().


The draw buffer is too small to hold the current draw state, the draw command and the data. Increase the size of the draw buffer, or decrease the number of points.


The following example:

void DrawSpan() {
    PgSpan_t    spans[152];
    PgSpan_t    *sp = spans;
    PhPoint_t   p = { 12, 10 };
    int         i, v, n=0;

    for (i=0; i<=100; i++) {
        sp->x1 = (i*i)>>6;
        v = 100 - i;
        sp->x2 = 160 - ((v*v)>>6);
        sp->y = i;
        sp++; n++;
    for (i=0; i<=50; i++) {
        sp->x1 = 100 - ((i*i)>>6);
        v = 50 - i;
        sp->x2 = 60 + ((v*v)>>6);
        sp->y = i+25;
        sp++; n++;
    PgSetFillColor( Pg_WHITE );
    PgDrawSpan( spans, n, &p, Pg_DRAW_FILL );

will draw:




Interrupt handler No
Signal handler No
Thread No

See also:

PgDrawPolygon*(), PgSetFillColor*(), PgSetStrokeColor*(), PgSetTextColor*(), PgFlush*(), PhPoint_t

Arcs, ellipses, polygons, and rectangles in the Raw Drawing and Animation chapter of the Photon Programmer's Guide