import plot2d_class;

D = matrix("double");

tri = zegraph("polygon");
xyz = zegraph("vertex");
tri:vertex(xyz);
tri:type("triangles");


function callback(west, east, south, north)
{
    if (west >= 180 || east <= 110 || south >= 80 || north <= 10) return;   // polygon outside the rectangle

    [n, m] = D:size();
    if (n < 3) return;    // discard bad polygon if any

    T = null;

    if (west >= 110 && east <= 180 && south >= 10 && north <= 80) {
        // polygon inside the rectangle
        T = D:triangulate();
    }
    else {
        // part of polygon inside the rectangle
        T = D:clip(110, 10, 71, 70);
        if (isuser(T)) T = T:triangulate();
    }

    if (isuser(T)) {
        // add data to triangle vertex
        [n, m] = T:size();
        if (n > 0) {
            T:insert(2, 0);
            [ptr, n, e] = T:ptr();
            xyz:add(ptr, n);
        }
    }
}

G = new Plot2D;
G->xaxis(range=[110, 180], tickmarks=[110, 10, 0]);
G->yaxis(range=[10, 80], tickmarks=[10, 10, 0]);
plot = G->c_plot:add(tri);

// let the callback function process coastline data

D:readgshhs("data\\gshhs_l.b", "land", "callback");
 
//G->show();

G->c_render:tofile("filled_map.png");