make multiselect dialogue rendering more efficient

[TheBearodactyl]

before:

demand-before.mp4

after:

demand-after.mp4

[gemini-code-assist]

Summary of Changes

Hello @TheBearodactyl, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request significantly refactors the terminal rendering mechanism for the multiselect dialogue. The primary goal is to enhance the visual smoothness and responsiveness of the interactive prompt by implementing a more granular and precise method for updating the terminal display, thereby minimizing visual artifacts like flickering.

Highlights

• Rendering Efficiency: The multiselect dialogue rendering has been made more efficient by replacing the clear_last_lines approach with a new reposition_and_write function. This change aims to reduce flickering and improve the user experience during terminal updates.
• State Management: The height field in the MultiSelect struct was renamed to last_line_count to more accurately reflect its purpose in tracking the number of lines rendered in the previous frame, which is crucial for the new rendering strategy.
• Terminal Interaction Refinement: A new cleanup function was introduced to handle the final state of the terminal cursor, ensuring it is correctly positioned after the multiselect operation concludes, replacing some previous clear calls.

Changelog

• src/multiselect.rs
  • Renamed height field to last_line_count in MultiSelect struct.
  • Replaced direct calls to clear() with reposition_and_write() for rendering updates.
  • Introduced reposition_and_write() function to handle cursor movement, line clearing, and writing output more efficiently.
  • Replaced clear() calls with cleanup() in exit conditions to ensure proper terminal state restoration.
  • Added a newline for better formatting before page number display.

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[gemini-code-assist]

Code Review

This pull request successfully refactors the rendering logic to be more efficient and reduce flickering by overwriting lines instead of clearing and re-rendering. The approach is solid. However, I've identified a regression in the cleanup function, which no longer clears the prompt upon cancellation. Additionally, I have a couple of suggestions for the new reposition_and_write function to further improve its efficiency and readability. Please see my detailed comments below.