Scroll Lock button support to lock the terminal from scrolling

[lcsondes]

Description of the new feature/enhancement

Support Scroll Lock to lock text from scrolling if I want to look at something that was briefly visible but is now off screen because there's a constant stream of new output from, e.g., compiling or watching some logs live with tail.

Proposed technical implementation details (optional)

If I have Scroll Lock on, new output arriving into the terminal should not scroll it down so I can keep reading what's currently visible on screen. Having Scroll Lock off would restore the behavior that's the only one as of writing.

[DHowett]

I agree. We've got a couple specs in flight here (#2529, for #980), and #3863 mentions scroll lock. Once we have keyboard selection (#2840 spec), that'll include keyboard buffer navigation, and we can extend #2529 to cover scroll lock as well. We're also considering "mark" mode (a mode you switch into where you can navigate the buffer solely by keyboard)

/dup #3863, #715

[ghost]

Hi! We've identified this issue as a duplicate of another one that already exists on this Issue Tracker. This specific instance is being closed in favor of tracking the concern over on the referenced thread. Thanks for your report!