message: fix(event): fix firefox version comparison flaw.
diff: @@ -9,6 +9,10 @@ import {isCanvasEl, transformCoordWithViewport} from './dom';
  const MOUSE_EVENT_REG = /^(?:mouse|pointer|contextmenu|drag|drop)|click/;
  const _calcOut: number[] = [];
  +const firefoxNotSupportOffsetXY = env.browser.firefox
  + // use offsetX/offsetY for Firefox >= 39
  + // PENDING: consider Firefox for Android and Firefox OS? >= 43
  + && +(env.browser.version as string).split('.')[0] < 39;
  type FirefoxMouseEvent = {
  layerX: number
  @@ -63,10 +67,7 @@ export function clientToLocal(
  // BTW2, (ev.offsetY || ev.pageY - $(ev.target).offset().top) is not correct in preserve-3d.
  // <https://bugs.jquery.com/ticket/8523#comment:14>
  // BTW3, In ff, offsetX/offsetY is always 0.
  - else if (env.browser.firefox
  - // use offsetX/offsetY for Firefox >= 39
  - // PENDING: consider Firefox for Android and Firefox OS? >= 43
  - && env.browser.version < '39'
  + else if (firefoxNotSupportOffsetXY
  && (e as FirefoxMouseEvent).layerX != null
  && (e as FirefoxMouseEvent).layerX !== (e as MouseEvent).offsetX
  ) {
  