en/builder/src/zrender/core/dom.js

import env from './env';
import { buildTransformer } from './fourPointsTransform';
var EVENT_SAVED_PROP = '___zrEVENTSAVED';
var _calcOut = [];
/**
 * Transform "local coord" from `elFrom` to `elTarget`.
 * "local coord": the coord based on the input `el`. The origin point is at
 *     the position of "left: 0; top: 0;" in the `el`.
 *
 * Support when CSS transform is used.
 *
 * Having the `out` (that is, `[outX, outY]`), we can create an DOM element
 * and set the CSS style as "left: outX; top: outY;" and append it to `elTarge`
 * to locate the element.
 *
 * For example, this code below positions a child of `document.body` on the event
 * point, no matter whether `body` has `margin`/`paddin`/`transfrom`/... :
 * ```js
 * transformLocalCoord(out, container, document.body, event.offsetX, event.offsetY);
 * if (!eqNaN(out[0])) {
 *     // Then locate the tip element on the event point.
 *     var tipEl = document.createElement('div');
 *     tipEl.style.cssText = 'position: absolute; left:' + out[0] + ';top:' + out[1] + ';';
 *     document.body.appendChild(tipEl);
 * }
 * ```
 *
 * Notice: In some env this method is not supported. If called, `out` will be `[NaN, NaN]`.
 *
 * @param {Array.<number>} out [inX: number, inY: number] The output..
 *        If can not transform, `out` will not be modified but return `false`.
 * @param {HTMLElement} elFrom The `[inX, inY]` is based on elFrom.
 * @param {HTMLElement} elTarget The `out` is based on elTarget.
 * @param {number} inX
 * @param {number} inY
 * @return {boolean} Whether transform successfully.
 */

export function transformLocalCoord(out, elFrom, elTarget, inX, inY) {
  return transformCoordWithViewport(_calcOut, elFrom, inX, inY, true) && transformCoordWithViewport(out, elTarget, _calcOut[0], _calcOut[1]);
}
/**
 * Transform between a "viewport coord" and a "local coord".
 * "viewport coord": the coord based on the left-top corner of the viewport
 *     of the browser.
 * "local coord": the coord based on the input `el`. The origin point is at
 *     the position of "left: 0; top: 0;" in the `el`.
 *
 * Support the case when CSS transform is used on el.
 *
 * @param {Array.<number>} out [inX: number, inY: number] The output. If `inverse: false`,
 *        it represents "local coord", otherwise "vireport coord".
 *        If can not transform, `out` will not be modified but return `false`.
 * @param {HTMLElement} el The "local coord" is based on the `el`, see comment above.
 * @param {number} inX If `inverse: false`,
 *        it represents "vireport coord", otherwise "local coord".
 * @param {number} inY If `inverse: false`,
 *        it represents "vireport coord", otherwise "local coord".
 * @param {boolean} [inverse=false]
 *        `true`: from "viewport coord" to "local coord".
 *        `false`: from "local coord" to "viewport coord".
 * @return {boolean} Whether transform successfully.
 */

export function transformCoordWithViewport(out, el, inX, inY, inverse) {
  if (el.getBoundingClientRect && env.domSupported && !isCanvasEl(el)) {
    var saved = el[EVENT_SAVED_PROP] || (el[EVENT_SAVED_PROP] = {});
    var markers = prepareCoordMarkers(el, saved);
    var transformer = preparePointerTransformer(markers, saved, inverse);

    if (transformer) {
      transformer(out, inX, inY);
      return true;
    }
  }

  return false;
}

function prepareCoordMarkers(el, saved) {
  var markers = saved.markers;

  if (markers) {
    return markers;
  }

  markers = saved.markers = [];
  var propLR = ['left', 'right'];
  var propTB = ['top', 'bottom'];

  for (var i = 0; i < 4; i++) {
    var marker = document.createElement('div');
    var stl = marker.style;
    var idxLR = i % 2;
    var idxTB = (i >> 1) % 2;
    stl.cssText = ['position: absolute', 'visibility: hidden', 'padding: 0', 'margin: 0', 'border-width: 0', 'user-select: none', 'width:0', 'height:0', // 'width: 5px',
    // 'height: 5px',
    propLR[idxLR] + ':0', propTB[idxTB] + ':0', propLR[1 - idxLR] + ':auto', propTB[1 - idxTB] + ':auto', ''].join('!important;');
    el.appendChild(marker);
    markers.push(marker);
  }

  return markers;
}

function preparePointerTransformer(markers, saved, inverse) {
  var transformerName = inverse ? 'invTrans' : 'trans';
  var transformer = saved[transformerName];
  var oldSrcCoords = saved.srcCoords;
  var oldCoordTheSame = true;
  var srcCoords = [];
  var destCoords = [];

  for (var i = 0; i < 4; i++) {
    var rect = markers[i].getBoundingClientRect();
    var ii = 2 * i;
    var x = rect.left;
    var y = rect.top;
    srcCoords.push(x, y);
    oldCoordTheSame = oldCoordTheSame && oldSrcCoords && x === oldSrcCoords[ii] && y === oldSrcCoords[ii + 1];
    destCoords.push(markers[i].offsetLeft, markers[i].offsetTop);
  } // Cache to avoid time consuming of `buildTransformer`.


  return oldCoordTheSame && transformer ? transformer : (saved.srcCoords = srcCoords, saved[transformerName] = inverse ? buildTransformer(destCoords, srcCoords) : buildTransformer(srcCoords, destCoords));
}

export function isCanvasEl(el) {
  return el.nodeName.toUpperCase() === 'CANVAS';
}