Function zoomClipped

src/plots/geo/zoom.js:201–300

(geo, projection)

// zoom for clipped projections
// inspired by https://www.jasondavies.com/maps/d3.geo.zoom.js
function zoomClipped(geo, projection) {
    var view = {r: projection.rotate(), k: projection.scale()};
    var zoom = initZoom(geo, projection);
    var event = d3eventDispatch(zoom, 'zoomstart', 'zoom', 'zoomend');
    var zooming = 0;
    var zoomOn = zoom.on;

    var zoomPoint;

    zoom.on('zoomstart', function() {
        d3.select(this).style(zoomstartStyle);

        var mouse0 = d3.mouse(this);
        var rotate0 = projection.rotate();
        var lastRotate = rotate0;
        var translate0 = projection.translate();
        var q = quaternionFromEuler(rotate0);

        zoomPoint = position(projection, mouse0);

        zoomOn.call(zoom, 'zoom', function() {
            var mouse1 = d3.mouse(this);

            projection.scale(view.k = d3.event.scale);

            if(!zoomPoint) {
                // if no zoomPoint, the mouse wasn't over the actual geography yet
                // maybe this point is the start... we'll find out next time!
                mouse0 = mouse1;
                zoomPoint = position(projection, mouse0);
            } else if(position(projection, mouse1)) {
                // check if the point is on the map
                // if not, don't do anything new but scale
                // if it is, then we can assume between will exist below
                // so we don't need the 'bank' function, whatever that is.

                // go back to original projection temporarily
                // except for scale... that's kind of independent?
                projection
                    .rotate(rotate0)
                    .translate(translate0);

                // calculate the new params
                var point1 = position(projection, mouse1);
                var between = rotateBetween(zoomPoint, point1);
                var newEuler = eulerFromQuaternion(multiply(q, between));
                var rotateAngles = view.r = unRoll(newEuler, zoomPoint, lastRotate);

                if(!isFinite(rotateAngles[0]) || !isFinite(rotateAngles[1]) ||
                   !isFinite(rotateAngles[2])) {
                    rotateAngles = lastRotate;
                }

                // update the projection
                projection.rotate(rotateAngles);
                lastRotate = rotateAngles;
            }