Terminal can lock up when typing if the cursor is hovering a link

[Tyriar]

VS Code issue: microsoft/vscode#169614

Repros in xterm.js:

1. Write a link
2. Hover it
3. Type slowly, it will get exponentially slower each character

[Tyriar]

Looks like the cause is that any viewport change registers a new event listener that only gets disposed when the original link is disposed:

xterm.js/src/browser/Linkifier2.ts

Line 314 in 3a74930

this._linkCacheDisposables.push(this._renderService.onRenderedViewportChange(e => {

[Tyriar]

This only happens when the link is on a different line to the cursor. This clear call doesn't end up clearing the old link otherwise, which is where the leak happens:

xterm.js/src/browser/Linkifier2.ts

Line 319 in 3a74930

this._clearCurrentLink(start, e.end + 1 + this._bufferService.buffer.ydisp);

Changing this to this._handleHover(position) fixes the problem for example because it ends up calling this._clearCurrentLink(undefined, undefined) which clears all links:

xterm.js/src/browser/Linkifier2.ts

Line 324 in 3a74930

this._askForLink(position, false);

https://github.com/Tyriar/xterm.js/blob/3a74930d072fe883c35ded5ee0052470ee44d470/src/browser/Linkifier2.ts#L328