webui: Dragging on the timeline is disabled when elements such as text or images are selected.

[junhaoliao]

Bug

Internal trials of the WebUI timeline has found that occasionally the timeline shows a "disabled" cursor when users drag on the timeline for zooming into a time range selection.

CLP version

2b55f93

Environment

Built with Ubuntu 22.04
Ran with official execution container

Reproduction steps

Through issue reproduction, it was determined that users might have unintentionally selected some text or empty element when they first attempt dragging on a region outside of the timeline chart. Then any further attempts to drag on the chart would also fail because those would be consider dropping the selection onto the chart, which is an undefined behaviour. As a result, the browser shows a "disabled" cursor which also impacted the chart's mousemove listener.

Reproduction video

1. NOTE: before dragging on the timeline, the mouse double-clicked outside of the chart region, which selected some empty element.
   https://github.com/y-scope/clp/assets/43196707/3e49dff7-a6ea-49cf-a377-714dda25de05
2. https://github.com/y-scope/clp/assets/43196707/4d95dfb4-1f18-4066-aca1-4502d307e3b3