editor: Add smooth cursor animation

[aiatsuk]

Implement Neovide-style smooth cursor movement for editor and terminal. The cursor smoothly animates to new positions using inertial physics.

Controlled by smooth_caret setting (true/false).

Closes #4991

Release Notes:

• Added smooth cursor animation for editor and terminal

[cla-bot]

We require contributors to sign our Contributor License Agreement, and we don't have @aiatsuk on file. You can sign our CLA at https://zed.dev/cla. Once you've signed, post a comment here that says '@cla-bot check'.

[aiatsuk]

@cla-bot check

[cla-bot]

The cla-bot has been summoned, and re-checked this pull request!

[Dima-369]

Thanks! I wondered:

With "smooth_caret": true (should definitely not be true by default) why is only crates/editor/src/inertial_cursor.rs used? There is also crates/editor/src/cursor_vfx.rs, but it can not be enabled in settings.json and the code does not use it directly?

So, it would be great if there would be Zed settings for smooth cursor configuration, basically for InertialCursorConfig. And since there is the VFX system already, how about user settings to actually use the VFX code and making CursorVfxConfig configurable in Zed settings?

Also, can you please provide screenshots/videos?

[MrSubidubi]

Thanks for this! Aside from the test failures, I still think that #39095 (comment) very much applies here - you use window.request_animation_frame, which basically calls a notify for the entity underneath. This would mean that we constantly rerender the entirety of the editor for minimal work every frame, which would be quite expensive.

Otherwise, I'd very much agree with what was said above, so please also provide some context on that. Thanks!

[aiatsuk]

With "smooth_caret": true (should definitely not be true by default) why is only crates/editor/src/inertial_cursor.rs used? There is also crates/editor/src/cursor_vfx.rs, but it can not be enabled in settings.json and the code does not use it directly?

You are absolutely right, I'll change that.

So, it would be great if there would be Zed settings for smooth cursor configuration, basically for InertialCursorConfig. And since there is the VFX system already, how about user settings to actually use the VFX code and making CursorVfxConfig configurable in Zed settings?

Currently, I'm simplifying the VFX system and remained for now only two options and added this to settings UI. I don't know if it's required to add the detailed configuration for the inertial cursor and for the VFX, so I propose to leave for now the toggle option and the select option for the effects.

Also, can you please provide screenshots/videos?

Sure, I'll add provide demo video