After prolong usage "selection-changed" stop firing

[amitm02]

After some prolog usage, selection-changed" events stop firing.
probably related to #1584

I've manage to track to problem to the following:

this.emitter.listenDOM('selectionchange', document, function () {
      if (mouseCount === 0) {
        setTimeout(_this.update.bind(_this, _emitter4.default.sources.USER), 1);
      }
    });

A breakpoint on that method revealed that mouseCount has a value > 0 (it was 8) and going up with each click.

the mouse-up event handler, that was suppose to keep mouseCount at 0 does not fired, but I couldn't figure out why:

this.emitter.listenDOM('mouseup', document.body, function () {
      mouseCount -= 1;
      if (mouseCount === 0) {
        _this.update(_emitter4.default.sources.USER);
      }
    });

[HWliao]

root cause: mousedown was triggered,but the museup was not triggered.
an operation causes this problem:
1.Press the mouse in the browser and do not release it
2.Move the mouse outside the browser
3.Release the mouse
Maybe we can write it like this:

    let mouseCount = 0;
    this.emitter.listenDOM('mousedown', document.body, () => {
      mouseCount  = 1;
    });
    this.emitter.listenDOM('mouseup', document.body, () => {
      mouseCount  = 0;
      if (mouseCount === 0) {
        this.update(Emitter.sources.USER);
      }
    });
    this.emitter.listenDOM('selectionchange', document, () => {
      if (mouseCount === 0) {
        setTimeout(this.update.bind(this, Emitter.sources.USER), 1);
      }
    });

The next time the mouse is uped, it can fix the mouseCount = 0
But not perfect`

[jhchen]

Thanks for looking into the cause @HWliao !

[sshearer-rsm]

Is there any idea on the timing for the next version with this commit?