Method _zoom

js/src/PanZoom.ts:225–260

(mouse_pos, delta)

  }

  _zoom(mouse_pos, delta) {
    if (delta) {
      if (delta > 0) {
        this.d3el.style('cursor', 'zoom-in');
      } else {
        this.d3el.style('cursor', 'zoom-out');
      }
      const mouse = { x: mouse_pos[0], y: mouse_pos[1] };
      const factor = Math.exp(-delta * 0.001);
      return this.scale_promises.then((scale_views) => {
        ['x', 'y'].forEach((dimension) => {
          scale_views[dimension].forEach((view: any, index) => {
            if (view.scale.invert) {
              // Categorical scales don't have an inversion.
              const scale = view.scale; //.copy().domain(this.domains_in_order[dimension][index]);
              // convert the initial domain to pixel coordinates
              let [domain_min, domain_max] = view.model.getDomainSliceInOrder();
              const pixel_min = scale(domain_min);
              const pixel_max = scale(domain_max);
              // take a weighted average between the mouse pos and the original pixel coordinate
              // and translate that back to the domain
              domain_min = scale.invert(
                (1 - factor) * mouse[dimension] + factor * pixel_min
              );
              domain_max = scale.invert(
                (1 - factor) * mouse[dimension] + factor * pixel_max
              );
              view.model.set('min', domain_min);
              view.model.set('max', domain_max);
              view.touch();
            }
          });
        });
      });
    }
  }

  active: boolean;
  scale_promises: Promise<Dict<Scale[]>>;