add smooth scrolling to chat

[uinstinct]

Description

Recently I was used Gemini Code Assist and the chat smooth scrolling (and last prompt's sticky behaviour) on a new prompt was something I liked. I wanted to add this to Continue as well.

Whenever a new prompt is given, the chat scrolls to the bottom in smoothly.

(I wanted to also add the sticky behaviour of the prompt. It would require changes to how we render the history items such that all other items remain constant during generation)

Checklist

• [] I've read the contributing guide
• [] The relevant docs, if any, have been updated or created
• [] The relevant tests, if any, have been updated or created

Screenshots

before.mp4

after.mp4

Testing instructions

1. open the chat messages area
2. add 2 or 3 prompts and long answers
3. see that when you prompt next, the last message is smoothly scrolled into view

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[Patrick-Erichsen]

The main difference here is that currently we just jump to the last prompt, but this instead smooth scrolls?

[Patrick-Erichsen]

Also it appears this change is breaking one of the e2e tests: https://github.com/continuedev/continue/actions/runs/14595994283/job/40979633741?pr=5290#step:13:85

[PlebeiusGaragicus]

instead - I like when the newly submitted prompt "pops" to the top of the window and as the agent reply streams it will again scroll once the window is filled.

[uinstinct]

The main difference here is that currently we just jump to the last prompt, but this instead smooth scrolls?

Yes, we jump to the last prompt using smooth scroll.

Also it appears this change is breaking one of the e2e tests: https://github.com/continuedev/continue/actions/runs/14595994283/job/40979633741?pr=5290#step:13:85

checking this and fixing

[uinstinct]

instead - I like when the newly submitted prompt "pops" to the top of the window and as the agent reply streams it will again scroll once the window is filled.

this will require some modifications to how we are rendering the history items as it was indicated here.

(I wanted to also add the sticky behaviour of the prompt. It would require changes to how we render the history items such that all other items remain constant during generation)

[Patrick-Erichsen]

cc @RomneyDa here, I think you'll have an opinion.

[RomneyDa]

@uinstinct this can look nice especially if there's a long delay up to first token. I think it ends up looking worse if you're on a tall screen and the model responds quickly, because it's still scrolling while the model starts responding. To make it scroll fast enough we'd have to have the scroll finish in a couple hundred milliseconds which at that point looks jenky.

Also, would need screenshots/more testing on truncating messages, one of the main reasons we abandoned autoscroll in the past was it often felt jenky when you go back and truncate the history at e.g. message 3/20

EDIT this was merged and then reverted #5408

[uinstinct]

Fair points @RomneyDa
I made a note of these these points and will try to add smooth scrolling once again. I think we will need to tweak how we are rendering the messages the above cases you mentioned and this one as well.