Function makeGraticule

src/plots/geo/geo.js:770–822

(axisName, geoLayout, fullLayout)

}

function makeGraticule(axisName, geoLayout, fullLayout) {
    // equivalent to the d3 "ε"
    var epsilon = 1e-6;
    // same as the geoGraticule default
    var precision = 2.5;

    var axLayout = geoLayout[axisName];
    var scopeDefaults = constants.scopeDefaults[geoLayout.scope];
    var rng;
    var oppRng;
    var coordFn;

    if(axisName === 'lonaxis') {
        rng = scopeDefaults.lonaxisRange;
        oppRng = scopeDefaults.lataxisRange;
        coordFn = function(v, l) { return [v, l]; };
    } else if(axisName === 'lataxis') {
        rng = scopeDefaults.lataxisRange;
        oppRng = scopeDefaults.lonaxisRange;
        coordFn = function(v, l) { return [l, v]; };
    }

    var dummyAx = {
        type: 'linear',
        range: [rng[0], rng[1] - epsilon],
        tick0: axLayout.tick0,
        dtick: axLayout.dtick
    };

    Axes.setConvert(dummyAx, fullLayout);
    var vals = Axes.calcTicks(dummyAx);

    // remove duplicate on antimeridian
    if(!geoLayout.isScoped && axisName === 'lonaxis') {
        vals.pop();
    }

    var len = vals.length;
    var coords = new Array(len);

    for(var i = 0; i < len; i++) {
        var v = vals[i].x;
        var line = coords[i] = [];
        for(var l = oppRng[0]; l < oppRng[1] + precision; l += precision) {
            line.push(coordFn(v, l));
        }
    }

    return {
        type: 'MultiLineString',
        coordinates: coords
    };
}

// Returns polygon GeoJSON corresponding to lon/lat range box
// with well-defined direction