@antv/g6/lib/behavior/zoom-canvas.js

graph visualization frame work

var DELTA = 0.05;
module.exports = {
  getDefaultCfg: function getDefaultCfg() {
    return {
      sensitivity: 2,
      minZoom: 0.1,
      maxZoom: 10
    };
  },
  getEvents: function getEvents() {
    return {
      wheel: 'onWheel'
    };
  },
  onWheel: function onWheel(e) {
    e.preventDefault();

    if (!this.shouldUpdate.call(this, e)) {
      return;
    }

    var graph = this.graph;
    var canvas = graph.get('canvas');
    var point = canvas.getPointByClient(e.clientX, e.clientY);
    var pixelRatio = canvas.get('pixelRatio');
    var sensitivity = this.get('sensitivity');
    var ratio = graph.getZoom(); // 兼容IE、Firefox及Chrome

    if (e.wheelDelta < 0) {
      ratio = 1 - DELTA * sensitivity;
    } else {
      ratio = 1 + DELTA * sensitivity;
    }

    var zoom = ratio * graph.getZoom();

    if (zoom > this.get('maxZoom') || zoom < this.get('minZoom')) {
      return;
    }

    graph.zoom(ratio, {
      x: point.x / pixelRatio,
      y: point.y / pixelRatio
    });
    graph.paint();
    graph.emit('wheelzoom', e);
  }
};