2 Commits

• docs: refine tui2 viewport roadmap (#8122)

  Update the tui2 viewport/history design doc with current status and a
  prioritized roadmap (scroll feel, selection/copy correctness, streaming
  wrap polish, terminal integration, and longer-term per-cell
  interactivity ideas).

  Josh McKinney · 2025-12-16 22:16:50 +00:00
  3fbf379e02
• WIP: Rework TUI viewport, history printing, and selection/copy (#7601)

  > large behavior change to how the TUI owns its viewport, history, and
  suspend behavior.
  > Core model is in place; a few items are still being polished before
  this is ready to merge.
  
  We've moved this over to a new tui2 crate from being directly on the tui
  crate.
  To enable use --enable tui2 (or the equivalent in your config.toml). See
  https://developers.openai.com/codex/local-config#feature-flags
  
  Note that this serves as a baseline for the changes that we're making to
  be applied rapidly. Tui2 may not track later changes in the main tui.
  It's experimental and may not be where we land on things.
  
  ---
  
  ## Summary
  
  This PR moves the Codex TUI off of “cooperating” with the terminal’s
  scrollback and onto a model
  where the in‑memory transcript is the single source of truth. The TUI
  now owns scrolling, selection,
  copy, and suspend/exit printing based on that transcript, and only
  writes to terminal scrollback in
  append‑only fashion on suspend/exit. It also fixes streaming wrapping so
  streamed responses reflow
  with the viewport, and introduces configuration to control whether we
  print history on suspend or
  only on exit.
  
  High‑level goals:
  
  - Ensure history is complete, ordered, and never silently dropped.
  - Print each logical history cell at most once into scrollback, even
  with resizes and suspends.
  - Make scrolling, selection, and copy match the visible transcript, not
  the terminal’s notion of
    scrollback.
  - Keep suspend/alt‑screen behavior predictable across terminals.
  
  ---
  
  ## Core Design Changes
  
  ### Transcript & viewport ownership
  
  - Treat the transcript as a list of **cells** (user prompts, agent
  messages, system/info rows,
    streaming segments).
  - On each frame:
  - Compute a **transcript region** as “full terminal frame minus the
  bottom input area”.
  - Flatten all cells into visual lines plus metadata (which cell + which
  line within that cell).
  - Use scroll state to choose which visual line is at the top of the
  region.
    - Clear that region and draw just the visible slice of lines.
  - The terminal’s scrollback is no longer part of the live layout
  algorithm; it is only ever written
    to when we decide to print history.
  
  ### User message styling
  
  - User prompts now render as clear blocks with:
    - A blank padding line above and below.
  - A full‑width background for every line in the block (including the
  prompt line itself).
  - The same block styling is used when we print history into scrollback,
  so the transcript looks
  consistent whether you are in the TUI or scrolling back after
  exit/suspend.
  
  ---
  
  ## Scrolling, Mouse, Selection, and Copy
  
  ### Scrolling
  
  - Scrolling is defined in terms of the flattened transcript lines:
    - Mouse wheel scrolls up/down by fixed line increments.
    - PgUp/PgDn/Home/End operate on the same scroll model.
  - The footer shows:
    - Whether you are “following live output” vs “scrolled up”.
    - Current scroll position (line / total).
  - When there is no history yet, the bottom pane is **pegged high** and
  gradually moves down as the
    transcript fills, matching the existing UX.
  
  ### Selection
  
  - Click‑and‑drag defines a **linear selection** over transcript
  line/column coordinates, not raw
    screen rows.
  - Selection is **content‑anchored**:
  - When you scroll, the selection moves with the underlying lines instead
  of sticking to a fixed
      Y position.
  - This holds both when scrolling manually and when new content streams
  in, as long as you are in
      “follow” mode.
  - The selection only covers the “transcript text” area:
    - Left gutter/prefix (bullets, markers) is intentionally excluded.
  - This keeps copy/paste cleaner and avoids including structural margin
  characters.
  
  ### Copy (`Ctrl+Y`)
  
  - Introduce a small clipboard abstraction (`ClipboardManager`‑style) and
  use a cross‑platform
    clipboard crate under the hood.
  - When `Ctrl+Y` is pressed and a non‑empty selection exists:
  - Re‑render the transcript region off‑screen using the same wrapping as
  the visible viewport.
  - Walk the selected line/column range over that buffer to reconstruct
  the exact text:
      - Includes spaces between words.
      - Preserves empty lines within the selection.
    - Send the resulting text to the system clipboard.
  - Show a short status message in the footer indicating success/failure.
  - Copy is **best‑effort**:
  - Clipboard failures (headless environment, sandbox, remote sessions)
  are handled gracefully via
      status messages; they do not crash the TUI.
  - Copy does *not* insert a new history entry; it only affects the status
  bar.
  
  ---
  
  ## Streaming and Wrapping
  
  ### Previous behavior
  
  Previously, streamed markdown:
  
  - Was wrapped at a fixed width **at commit time** inside the streaming
  collector.
  - Those wrapped `Line<'static>` values were then wrapped again at
  display time.
  - As a result, streamed paragraphs could not “un‑wrap” when the terminal
  width increased; they were
    permanently split according to the width at the start of the stream.
  
  ### New behavior
  
  This PR implements the first step from
  `codex-rs/tui/streaming_wrapping_design.md`:
  
  - Streaming collector is constructed **without** a fixed width for
  wrapping.
    - It still:
      - Buffers the full markdown source for the current stream.
      - Commits only at newline boundaries.
      - Emits logical lines as new content becomes available.
  - Agent message cells now wrap streamed content only at **display
  time**, based on the current
    viewport width, just like non‑streaming messages.
  - Consequences:
    - Streamed responses reflow correctly when the terminal is resized.
  - Animation steps are per logical line instead of per “pre‑wrapped”
  visual line; this makes some
  commits slightly larger but keeps the behavior simple and predictable.
  
  Streaming responses are still represented as a sequence of logical
  history entries (first line +
  continuations) and integrate with the same scrolling, selection, and
  printing model.
  
  ---
  
  ## Printing History on Suspend and Exit
  
  ### High‑water mark and append‑only scrollback
  
  - Introduce a **cell‑based high‑water mark** (`printed_history_cells`)
  on the transcript:
  - Represents “how many cells at the front of the transcript have already
  been printed”.
    - Completely independent of wrapped line counts or terminal geometry.
  - Whenever we print history (suspend or exit):
  - Take the suffix of `transcript_cells` beyond `printed_history_cells`.
    - Render just that suffix into styled lines at the **current** width.
    - Write those lines to stdout.
    - Advance `printed_history_cells` to cover all cells we just printed.
  - Older cells are never re‑rendered for scrollback. They stay in
  whatever wrapping they had when
  printed, which is acceptable as long as the logical content is present
  once.
  
  ### Suspend (`Ctrl+Z`)
  
  - On suspend:
    - Leave alt screen if active and restore normal terminal modes.
  - Render the not‑yet‑printed suffix of the transcript and append it to
  normal scrollback.
    - Advance the high‑water mark.
    - Suspend the process.
  - On resume (`fg`):
    - Re‑enter the TUI mode (alt screen + input modes).
  - Clear the viewport region and fully redraw from in‑memory transcript
  and state.
  
  This gives predictable behavior across terminals without trying to
  maintain scrollback live.
  
  ### Exit
  
  - On exit:
    - Render any remaining unprinted cells once and write them to stdout.
  - Add an extra blank line after the final Codex history cell before
  printing token usage, so the
      transcript and usage info are visually separated.
  - If you never suspended, exit prints the entire transcript exactly
  once.
  - If you suspended one or more times, exit prints only the cells
  appended after the last suspend.
  
  ---
  
  ## Configuration: Suspend Printing
  
  This PR also adds configuration to control **when** we print history:
  
  - New TUI config option to gate printing on suspend:
    - At minimum:
  - `print_on_suspend = true` – current behavior: print new history at
  each suspend *and* on exit.
      - `print_on_suspend = false` – only print on exit.
  - Default is tuned to preserve current behavior, but this can be
  revisited based on feedback.
  - The config is respected in the suspend path:
  - If disabled, suspend only restores terminal modes and stops rendering
  but does not print new
      history.
    - Exit still prints the full not‑yet‑printed suffix once.
  
  This keeps the core viewport logic agnostic to preference, while letting
  users who care about
  quiet scrollback opt out of suspend printing.
  
  ---
  
  ## Tradeoffs
  
  What we gain:
  
  - A single authoritative history model (the in‑memory transcript).
  - Deterministic viewport rendering independent of terminal quirks.
  - Suspend/exit flows that:
    - Print each logical history cell exactly once.
    - Work across resizes and different terminals.
    - Interact cleanly with alt screen and raw‑mode toggling.
  - Consistent, content‑anchored scrolling, selection, and copy.
  - Streaming messages that reflow correctly with the viewport width.
  
  What we accept:
  
  - Scrollback may contain older cells wrapped differently than newer
  ones.
  - Streaming responses appear in scrollback as a sequence of blocks
  corresponding to their streaming
    structure, not as a single retroactively reflowed paragraph.
  - We do not attempt to rewrite or reflow already‑printed scrollback.
  
  For deeper rationale and diagrams, see
  `docs/tui_viewport_and_history.md` and
  `codex-rs/tui/streaming_wrapping_design.md`.
  
  ---
  
  ## Still to Do Before This PR Is Ready
  
  These are scoped to this PR (not long‑term future work):
  
  - [ ] **Streaming wrapping polish**
    - Double‑check all streaming paths use display‑time wrapping only.
    - Ensure tests cover resizing after streaming has started.
  
  - [ ] **Suspend printing config**
  - Finalize config shape and default (keep existing behavior vs opt‑out).
  - Wire config through TUI startup and document it in the appropriate
  config docs.
  
  - [x] **Bottom pane positioning**
  - Ensure the bottom pane is pegged high when there’s no history and
  smoothly moves down as the
  transcript fills, matching the current behavior across startup and
  resume.
  
  - [x] **Transcript mouse scrolling**
  - Re‑enable wheel‑based transcript scrolling on top of the new scroll
  model.
  - Make sure mouse scroll does not get confused with “alternate scroll”
  modes from terminals.
  
  - [x] **Mouse selection vs streaming**
  - When selection is active, stop auto‑scrolling on streaming so the
  selection remains stable on
      the selected content.
  - Ensure that when streaming continues after selection is cleared,
  “follow latest output” mode
      resumes correctly.
  
  - [ ] **Auto‑scroll during drag**
  - While the user is dragging a selection, auto‑scroll when the cursor is
  at/near the top or bottom
  of the transcript viewport to allow selecting beyond the current visible
  window.
  
  - [ ] **Feature flag / rollout**
  - Investigate gating the new viewport/history behavior behind a feature
  flag for initial rollout,
  so we can fall back to the old behavior if needed during early testing.
  
  - [ ] **Before/after videos**
    - Capture short clips showing:
      - Scrolling (mouse + keys).
      - Selection and copy.
      - Streaming behavior under resize.
      - Suspend/resume and exit printing.
    - Use these to validate UX and share context in the PR discussion.

  Josh McKinney · 2025-12-15 17:20:53 -08:00
  b093565bfb