gistfile1.c

// not checking error codes cause YOLO

void
plot_dots(OGRLayerH layer, cairo_t *ctx, simplet_map_t *map, const char *color){
  OGRFeatureH feature;
  while((feature = OGR_L_GetNextFeature(layer))){
    int num = OGR_F_GetFieldAsInteger(feature, 0);
    OGRGeometryH geom = OGR_F_GetGeometryRef(feature);
    OGR_G_TransformTo(geom, map->proj);
    OGREnvelope env;
    OGR_G_GetEnvelope(geom, &env);
    double width  = env.MaxX - env.MinX;
    double height = env.MaxY - env.MinY;
    while(num > 0){
      double x = env.MinX + drand48() * width;
      double y = env.MinY + drand48() * height;
      OGRGeometryH *pt = OGR_G_CreateGeometry(wkbPoint);
      printf(".");
      OGR_G_AddPoint_2D(pt, x, y);
      if(OGR_G_Within(pt, geom)) {
        printf("%d", num);
        cairo_move_to(ctx, x, y);
        double rad = 0.5, dy = 0;
        cairo_save(ctx);
        cairo_device_to_user_distance(ctx, &rad, &dy);
        cairo_new_path(ctx);
        cairo_arc(ctx,  x - rad / 2, y - rad / 2, rad, 0., 2 * SIMPLET_PI);
        cairo_user_to_device_distance(ctx, &y, &x);
        unsigned int r, g, b, a;
        simplet_parse_color(color, &r, &g, &b, &a);
        cairo_set_source_rgba(ctx, r / 255.0, g / 255.0, b / 255.0, a / 255.0);
        cairo_fill(ctx);
        cairo_close_path(ctx);
        cairo_restore(ctx);
        num--;
      }
      fflush(stdout);
      OGR_G_DestroyGeometry(pt);
    }
    puts("");
  }
}