wide margins with empty days around activities (undocumented scrollableHorizonFactor)

[watery]

This can be seen in the Activity Chart example:

By scrolling to the left of the first activity, a lot of days are present, but empty; the same is rendered to the right, after the last activity.

I've tracked down this behavoiur to these lines:

gantt-chart/packages/ibm-gantt-chart/src/jquery/timeline/timeline.js

Lines 38 to 41 in f72eea3

	this.scrollableHorizon = {
	start: Math.round(start - ((this.scrollableHorizonFactor - 1) / 2) * span),
	end: Math.round(end + ((this.scrollableHorizonFactor - 1) / 2) * span),
	};

Where scrollableHorizonFactor is used to calculate the (vis) Timeline component start and end parameters from the activity times. It can be configured too, thus giving it a value of e.g. 1.2 brings the component to a much narrow size:

const config = {
  scrollableHorizonFactor: 1.2,
  type: Gantt.type.ACTIVITY_CHART,
  data: {

A couple of notes:

1. the configuration parameter is undocumented
2. it is still a multiplicative factor, so the wider the span (difference between the start of the earlier activity and end of the later one) the bigger the empty timeline areas - it would be better if a fixed margin / padding was available

[watery]

Configuring the timeWindow seems to have an effect on the timetable area, so with:

const config = {
  scrollableHorizonFactor: 1,
  type: Gantt.type.ACTIVITY_CHART,
  data: {
    timeWindow: {
        data: {
          start: '2023-04-01 00:00:00',
          end: '2023-05-16 00:00:00',
        },
    },
    dateFormat : "yyyy-MM-dd HH:mm:ss",

The whole chart can be centered and maximized so there's almost no need for horizontal scrolling.