Collapse of subgroup background when scrolling to point of no data

[brucetrask]

Hello,

I am using vis.js 4.21.0 and I am using the timeline feature within that. I am using Firefox on Windows.

I have a use where I am using subgroups much like the subgroup example. Subgroups is a great feature. Thanks for adding it.

I noticed some behavior which I was hoping could be fixed. Everything works fine until I start to scroll to the right and as the data items fall out of view to the left, the background colors and names stay in place for a bit but then eventually vanish (the name) and the background color collapses to a small strip. In my use of it I want to keep those as they always are so as to give me a complete picture as I go. I have attached an example of what I am seeing. I have also attached the screenshots of the various phases of what I am seeing. The issue shows up when you load the file, then scroll to the right. As you go the subgroup backgrounds collapse and the names for them also disappear.

subgroupstest.txt

[mojoaxel]

@brucetrask Thanks for the example code, but could you please host this in something like jsbin.