Text selection scrolling in SC.ScrollView

autoscroll_text_support.js

SC.AutoScrollTextSupport = {

  scrollView: function () {
    var view = this.get('parentView');

    while (view && !view.isScrollable) {
      view = view.get('parentView');
    }

    return view;
  }.property('parentView').cacheable(),

  mouseDown: function (evt) {
    this._mouseDown = YES;
    evt.allowDefault();
    return YES;
  },

  mouseMoved: function (evt) {
    if (this._mouseDown) {
      return this.mouseDragged(evt);
    }
    return NO;
  },

  mouseUp: function (evt) {
    this._mouseDown = NO;
    if (this._timer) {
      this._timer.invalidate();
    }
    evt.allowDefault();
    return YES;
  },

  mouseDragged: function (evt) {
    var scrollView = this.get('scrollView'),
        frame = scrollView.get('frame'),
        offset = SC.offset(scrollView.$()),
        point = { x: evt.pageX, y: evt.pageY };

    frame.x = offset.x;
    frame.y = offset.y;

    if (!SC.pointInRect(point, frame)) {
      this._scrollY = point.y - frame.y;
      if (this._scrollY > 0) {
        if (this._scrollY < frame.height) {
          this._scrollY = 0;
        } else {
          this._scrollY -= frame.height;
        }
      }
      this._scrollY = Math.min(this._scrollY / 2, 30);

      this._autoscroll();
      this._timer = SC.Timer.schedule({
        target: this,
        action: '_autoscroll',
        interval: 250,
        repeats: YES
      });
    } else {
      this._scrollY = 0;
      if (this._timer) {
        this._timer.invalidate();
      }
    }
    return YES;
  },

  _autoscroll: function () {
    this.get('scrollView').scrollBy(0, this._scrollY);
  }
};