DOM Renderer: display underline when selection link content

[tisilent]

https://github.com/xtermjs/xterm.js/assets/48614781/61096ded-c568-4f85-881c-a012062a2dbc

[jerch]

Regarding link handling the DOM renderer is pretty straight forward - it re-renders a line with underlines applied/remove from the linkifier events. A quickfix is prolly possible by internally eval'ing the selection state.

A better long-term fix would involve changes on the linkifier, as the question here is, why it sends link events for selections in the first place. The mouse listeneners are quite scattered over the codebase currently, imho we would need a proper mouse listener service as a global orchestrator to fix this more reliably in the future.

[tisilent]

Fixed it, there is still an issue where the dashed line will not be visible. 🤪

[tisilent]

Two types of underline can be displayed simultaneously. But this method doesn't feel very good. Need to process the curve...... 👻