Support hold & drag to scroll pipeline overview
Release notes
Problem to solve
When you have large pipelines (such as in our main GitLab project) that overflow both horizontally and vertically, it's not obvious how to scroll horizontally:
If you scroll all the way down you'll see the horizontal scrollbar (this is in Firefox):
My mouse also has a horizontal scroll wheel, but I don't think this is very common. In Firefox it also scrolls really slowly by default, although I was able to fix that by increasing mousewheel.default.delta_multiplier_x in about:config.
Intended users
Everybody interacting with pipelines.
User experience goal
The pipeline overview should be easy and pleasant to scroll.
Proposal
Allow hold & dragging the mouse on blank space to move around the view, similar to how this works in e.g. Trello boards.
Further details
The Issue Board suffers from the same problem, and we could use the same solution I proposed there: #16085 (comment 219434720)