ds->visible = snewn(ds->w * ds->h, unsigned char);
ds->tilesize = 0; /* not decided yet */
memset(ds->visible, 255, ds->w * ds->h);
ds->visible = snewn(ds->w * ds->h, unsigned char);
ds->tilesize = 0; /* not decided yet */
memset(ds->visible, 255, ds->w * ds->h);