This is a follow-up to https://github.com/openai/codex/pull/15922. That
previous PR deleted the old `tui` directory and left the new
`tui_app_server` directory in place. This PR renames `tui_app_server` to
`tui` and fixes up all references.
This is the part 1 of 2 PRs that will delete the `tui` /
`tui_app_server` split. This part simply deletes the existing `tui`
directory and marks the `tui_app_server` feature flag as removed. I left
the `tui_app_server` feature flag in place for now so its presence
doesn't result in an error. It is simply ignored.
Part 2 will rename the `tui_app_server` directory `tui`. I did this as
two parts to reduce visible code churn.
## Problem
Diff lines used only foreground colors (green/red) with no background
tinting, making them hard to scan. The gutter (line numbers) also had no
theme awareness — dimmed text was fine on dark terminals but unreadable
on light ones.
## Mental model
Each diff line now has four styled layers: **gutter** (line number),
**sign** (`+`/`-`), **content** (text), and **line background** (full
terminal width). A `DiffTheme` enum (`Dark` / `Light`) is selected once
per render by probing the terminal's queried background via
`default_bg()`. A companion `DiffColorLevel` enum (`TrueColor` /
`Ansi256` / `Ansi16`) is derived from `stdout_color_level()` and gates
which palette is used. All style helpers dispatch on `(theme,
DiffLineType, color_level)` to pick the right colors.
| Theme Picker Wide | Theme Picker Narrow |
|---|---|
| <img width="1552" height="1012" alt="image"
src="https://github.com/user-attachments/assets/231b21b7-32d4-4727-80ed-7d01924954be"
/> | <img width="795" height="1012" alt="image"
src="https://github.com/user-attachments/assets/549cacdf-daec-43c9-ad64-2a28d16d140e"
/> |
| Dark BG - 16 colors | Dark BG - 256 colors | Dark BG - True Colors |
|---|---|---|
| <img width="1552" height="1012" alt="dark-16colors"
src="https://github.com/user-attachments/assets/fba36de3-c101-47d4-9e63-88cdd00410d0"
/> | <img width="1552" height="1012" alt="dark-256colors"
src="https://github.com/user-attachments/assets/f39e4307-c6b0-49c4-b4fe-bd26d3d8e41c"
/> | <img width="1552" height="1012" alt="dark-truecolor"
src="https://github.com/user-attachments/assets/1af4ec57-04bf-4dfb-8a44-0ab5e5aaaf18"
/> |
| Light BG - 16 colors | Light BG - 256 colors | Light BG - True Colors
|
|---|---|---|
| <img width="1552" height="1012" alt="light-16colors"
src="https://github.com/user-attachments/assets/2b5423d1-74b4-4b1e-8123-7c2488ff436b"
/> | <img width="1552" height="1012" alt="light-256colors"
src="https://github.com/user-attachments/assets/c94cff9a-8d3e-42c9-bbe7-079da39953a8"
/> | <img width="1552" height="1012" alt="light-truecolor"
src="https://github.com/user-attachments/assets/f73da626-725f-4452-99ee-69ef706df2c6"
/> |
## Non-goals
- No runtime theme switching beyond what `default_bg()` already
provides.
- No change to syntax highlighting theme selection or the highlight
module.
## Tradeoffs
- Three fixed palettes (truecolor RGB, 256-color indexed, 16-color
named) are maintained rather than using `best_color` nearest-match. This
is deliberate: `supports_color::on_cached(Stream::Stdout)` can misreport
capabilities once crossterm enters the alternate screen, so hand-picked
palette entries give better visual results than automatic quantization.
- Delete lines in the syntax-highlighted path get `Modifier::DIM` to
visually recede compared to insert lines. This trades some readability
of deleted code for scan-ability of additions.
- The theme picker's diff preview sets `preserve_side_content_bg: true`
on `ListSelectionView` so diff background tints survive into the side
panel. Other popups keep the default (`false`) to preserve their
reset-background look.
## Architecture
- **Color constants** are module-level `const` items grouped by palette
tier: `DARK_TC_*` / `LIGHT_TC_*` (truecolor RGB tuples), `DARK_256_*` /
`LIGHT_256_*` (xterm indexed), with named `Color` variants used for the
16-color tier.
- **`DiffTheme`** is a private enum; `diff_theme()` probes the terminal
and `diff_theme_for_bg()` is the testable pure-function version.
- **`DiffColorLevel`** is a private enum derived from `StdoutColorLevel`
via `diff_color_level()`.
- **Palette helpers** (`add_line_bg`, `del_line_bg`, `light_gutter_fg`,
`light_add_num_bg`, `light_del_num_bg`) each take `(DiffTheme,
DiffColorLevel)` or just `DiffColorLevel` and return a `Color`.
- **Style helpers** (`style_line_bg_for`, `style_gutter_for`,
`style_sign_add`, `style_sign_del`, `style_add`, `style_del`) each take
`(DiffLineType, DiffTheme, DiffColorLevel)` or `(DiffTheme,
DiffColorLevel)` and return a `Style`.
- **`push_wrapped_diff_line_inner_with_theme_and_color_level`** is the
innermost renderer, accepting both theme and color level so tests can
exercise any combination without depending on the terminal.
- **Line-level background** is applied via
`RtLine::from(...).style(line_bg)` so the tint extends across the full
terminal width, not just the text content.
- **Theme picker integration**: `ListSelectionView` gained a
`preserve_side_content_bg` flag. When `true`, the side panel skips
`force_bg_to_terminal_bg`, letting diff preview backgrounds render
faithfully.
## Observability
No new logging. Theme selection is deterministic from `default_bg()`,
which is already queried and cached at TUI startup.
## Tests
1. **`DiffTheme` is determined per `render_change` call** — if
`default_bg()` changes mid-render (e.g. `requery_default_colors()`
fires), different file chunks could render with different themes. Low
risk in practice since re-query only happens on explicit user action.
2. **16-color tier uses named `Color` variants** (`Color::Green`,
`Color::Red`, etc.) which the terminal maps to its own palette. On
unusual terminal themes these could clash with the background.
Acceptable since 16-color terminals already have unpredictable color
rendering.
3. **Light-theme `style_add` / `style_del` set bg but no fg** — on light
terminals, non-syntax-highlighted content uses the terminal's default
foreground against a pastel background. If the terminal's default fg
happens to be very light, contrast could suffer. This is an edge case
since light-terminal users typically have dark default fg.
4. **`preserve_side_content_bg` is a general-purpose flag but only used
by the theme picker** — if other popups start using side content with
intentional backgrounds they'll need to opt in explicitly. Not a real
risk today, just a note for future callers.
The transcript viewport draws every frame. Ratatui's Line::render_ref
does grapheme segmentation and span layout, so repeated redraws can burn
CPU during streaming even when the visible transcript hasn't changed.
Introduce TranscriptViewCache to reduce per-frame work:
- WrappedTranscriptCache memoizes flattened+wrapped transcript lines per
width, appends incrementally as new cells arrive, and rebuilds on width
change, truncation (backtrack), or transcript replacement.
- TranscriptRasterCache caches rasterized rows (Vec<Cell>) per line
index and user-row styling; redraws copy cells instead of rerendering
spans.
The caches are width-scoped and store base transcript content only;
selection highlighting and copy affordances are applied after drawing.
User rows include the row-wide base style in the cached raster.
Refactor transcript_render to expose append_wrapped_transcript_cell for
incremental building and add a test that incremental append matches the
full build.
Add docs/tui2/performance-testing.md as a playbook for macOS sample
profiles and hotspot greps.
Expand transcript_view_cache tests to cover rebuild conditions, raster
equivalence vs direct rendering, user-row caching, and eviction.
Test: cargo test -p codex-tui2
Instead of querying all 256 terminal colors on startup, which was slow
in some terminals, hardcode the default xterm palette.
Additionally, tweak the shimmer so that it blends between default_fg and
default_bg, instead of "dark gray" (according to the terminal) and pure
white (regardless of terminal theme).
