identity.js

import clipRectangle from "../clip/rectangle";
import identity from "../identity";
import {transformer} from "../transform";
import {fitExtent, fitSize, fitWidth, fitHeight} from "./fit";

function scaleTranslate(kx, ky, tx, ty) {
  return kx === 1 && ky === 1 && tx === 0 && ty === 0 ? identity : transformer({
    point: function(x, y) {
      this.stream.point(x * kx + tx, y * ky + ty);
    }
  });
}

export default function() {
  var k = 1, tx = 0, ty = 0, sx = 1, sy = 1, transform = identity, // scale, translate and reflect
      x0 = null, y0, x1, y1, // clip extent
      postclip = identity,
      cache,
      cacheStream,
      projection;

  function reset() {
    cache = cacheStream = null;
    return projection;
  }

  return projection = {
    stream: function(stream) {
      return cache && cacheStream === stream ? cache : cache = transform(postclip(cacheStream = stream));
    },
    postclip: function(_) {
      return arguments.length ? (postclip = _, x0 = y0 = x1 = y1 = null, reset()) : postclip;
    },
    clipExtent: function(_) {
      return arguments.length ? (postclip = _ == null ? (x0 = y0 = x1 = y1 = null, identity) : clipRectangle(x0 = +_[0][0], y0 = +_[0][1], x1 = +_[1][0], y1 = +_[1][1]), reset()) : x0 == null ? null : [[x0, y0], [x1, y1]];
    },
    scale: function(_) {
      return arguments.length ? (transform = scaleTranslate((k = +_) * sx, k * sy, tx, ty), reset()) : k;
    },
    translate: function(_) {
      return arguments.length ? (transform = scaleTranslate(k * sx, k * sy, tx = +_[0], ty = +_[1]), reset()) : [tx, ty];
    },
    reflectX: function(_) {
      return arguments.length ? (transform = scaleTranslate(k * (sx = _ ? -1 : 1), k * sy, tx, ty), reset()) : sx < 0;
    },
    reflectY: function(_) {
      return arguments.length ? (transform = scaleTranslate(k * sx, k * (sy = _ ? -1 : 1), tx, ty), reset()) : sy < 0;
    },
    fitExtent: function(extent, object) {
      return fitExtent(projection, extent, object);
    },
    fitSize: function(size, object) {
      return fitSize(projection, size, object);
    },
    fitWidth: function(width, object) {
      return fitWidth(projection, width, object);
    },
    fitHeight: function(height, object) {
      return fitHeight(projection, height, object);
    }
  };
}