Add accessibility baseline: no-color and reduced motion

docs/accessibility/baseline.md

@@ -0,0 +1,36 @@
+# Accessibility and reduced-presentation baseline
+
+This applies to NMSh-owned surfaces only: panels, the composer, status rows, help and the transcript chrome. Raw PTY output, archived command output and `/copy` are never restyled.
+
+Accessibility flows through the shared primitives (`ui/palette`, `ui/glyphs`, `ui/actions`, `ui/formControls`, `presentation/environment`), not a separate renderer.
+
+## Controls
+
+| Setting | Effect |
+| --- | --- |
+| `NO_COLOR=1` (non-empty) or `TERM=dumb` | `foreground()`/`background()` emit nothing. Bold, inverse and glyphs remain. |
+| `NMSH_COLOR=none` / `truecolor` | Explicit override, wins over `NO_COLOR`/`TERM`. |
+| `NMSH_ICONS=safe` | ASCII-safe glyph set (existing). |
+| `NMSH_REDUCED_MOTION=1` | Shimmer/activity glyph phase and the welcome blink stay still. Durations keep counting. Deterministic presentation implies it. |
+
+These are environment controls. A persisted setting would change the public configuration schema and is left to the Settings work.
+
+## Acceptance criteria
+
+1. Every action is reachable by keyboard; the pointer only adds shortcuts (`ui/actions`).
+2. The focused row is identifiable without color: a pointer glyph (`›`, or `>` in safe mode) or `>` in plain form controls.
+3. Changed and error states are text (`(changed)`, `Error: ...`), not color alone (`ui/formControls`).
+4. Success/failure rows carry distinct glyphs (`✔`/`✘`, or `+`/`x` in safe mode) in addition to color.
+5. With `NO_COLOR`, no NMSh-generated color escape is written; layout is unchanged.
+6. With reduced motion, no NMSh-owned decoration changes between frames unless state changes.
+7. No width-changing animation.
+
+## Audit result
+
+- Met: keyboard operation in palette, Settings, draft panels; pointer-free navigation; safe glyph set; status glyphs; footer help derived from actions.
+- Known gaps: command-row background bands (`TranscriptPresenter`) are a color-only cue for "this is a command" under `NO_COLOR`; the prompt prefix is the remaining cue. Provider panels (prompt, welcome, suggestions) keep hand-written footers.
+- Not supported: 256-color/16-color downconversion (planned with the Chroma work, #171) and a persisted reduced-motion setting.
+
+## Screen readers
+
+NMSh redraws full-screen frames in the alternate screen. Terminals expose that to assistive technology inconsistently, so NMSh cannot guarantee screen-reader-friendly output. What it does provide is text-carried state and no pointer requirement; behavior with a specific terminal and reader has not been verified.

src/app/TerminalApp.ts

@@ -54,7 +54,7 @@ import {shouldPassthrough} from '../passthrough/PassthroughPolicy.js';
 import {layoutInput, graphemes} from '../input/inputLayout.js';
 import {editText} from '../ui/formControls.js';
 import {shimmerText} from '../status/shimmer.js';
-import {isDeterministicPresentation, presentationAnimationElapsed, presentationCompletionTime, presentationNow} from '../presentation/environment.js';
+import {isReducedMotion, presentationAnimationElapsed, presentationCompletionTime, presentationNow} from '../presentation/environment.js';
 import {TaskProgress} from '../status/TaskProgress.js';
 import {completedActivity, liveActivityParts} from '../status/activity.js';
 import {extractFacts} from '../status/adapters.js';
@@ -98,7 +98,7 @@ const FLOW_EDIT_KEYS: ReadonlySet<Key['kind']> = new Set(['text', 'paste', 'back
 const STOPPED = foreground({red: 198, green: 156, blue: 109});
 const INFO = SECONDARY;
 const RESET = '\u001B[0m';
-const PASTE_ATOM_BACKGROUND = '\u001B[48;2;63;65;82m';
+const PASTE_ATOM_BACKGROUND = background({red: 63, green: 65, blue: 82});
 const STATUS_REFRESH_MS = 100;
 
 export class TerminalApp {
@@ -2401,7 +2401,7 @@ export class TerminalApp {
    * change. Blinks are skipped (not queued) while no welcome is present.
    */
   private scheduleWelcomeBlink(): void {
-    if (this.stopped || isDeterministicPresentation()) return;
+    if (this.stopped || isReducedMotion()) return;
     this.welcomeBlinkTimer = setTimeout(() => {
       if (this.stopped) return;
       if (!this.output.hasWelcome || this.passthrough) {
@@ -2680,7 +2680,7 @@ export class TerminalApp {
     const isActive = (Date.now() - this.lastOutputTime) < 750;
     const animationElapsed = presentationAnimationElapsed(elapsed);
     const parts = liveActivityParts(this.running.command, elapsed, animationElapsed);
-    return `${shimmerText(parts.phrase, animationElapsed, isDeterministicPresentation() ? false : isActive)}${SECONDARY}${parts.duration}${RESET}`;
+    return `${shimmerText(parts.phrase, animationElapsed, isReducedMotion() ? false : isActive)}${SECONDARY}${parts.duration}${RESET}`;
   }
 
   private jumpAffordance(columns: number): string {

src/output/TranscriptPresenter.ts

@@ -1,6 +1,6 @@
 import {type StyledLine} from './AnsiOutputParser.js';
 import {wrapStyledLine, type WrappedRow} from './viewport.js';
-import {foreground, UI_COLORS} from '../ui/palette.js';
+import {background, foreground, UI_COLORS} from '../ui/palette.js';
 import {GLYPHS} from '../ui/glyphs.js';
 import {displayWidth, repeatToWidth, stripAnsi, truncateAnsi, truncateText} from '../util/text.js';
 import {formatDuration} from '../status/commandTiming.js';
@@ -21,9 +21,9 @@ const SECONDARY = foreground(UI_COLORS.secondary);
 const SUBTLE = foreground(UI_COLORS.subtle);
 const RESET = '\u001B[0m';
 /** Row surfaces: submitted command rows, hovered and focused disclosure rows. */
-const COMMAND_SURFACE = '\u001B[48;2;38;38;48m';
-const HOVER_SURFACE = '\u001B[48;2;45;45;55m';
-const FOCUS_SURFACE = '\u001B[48;2;60;60;80m';
+const COMMAND_SURFACE = background({red: 38, green: 38, blue: 48});
+const HOVER_SURFACE = background({red: 45, green: 45, blue: 55});
+const FOCUS_SURFACE = background({red: 60, green: 60, blue: 80});
 
 /** Transcript presentation: Normal rows, or Chat with right-aligned command blocks. */
 export type TranscriptLayout = 'normal' | 'chat';
@@ -470,7 +470,7 @@ export function renderHistoricalContext(context: HistoricalContextSnapshot, widt
 }
 
 function rgbStyle(foregroundColor?: Rgb, backgroundColor?: Rgb): string {
-  const fg = foregroundColor ? `\u001B[38;2;${foregroundColor.red};${foregroundColor.green};${foregroundColor.blue}m` : '';
-  const bg = backgroundColor ? `\u001B[48;2;${backgroundColor.red};${backgroundColor.green};${backgroundColor.blue}m` : '\u001B[49m';
+  const fg = foregroundColor ? foreground(foregroundColor) : '';
+  const bg = backgroundColor ? background(backgroundColor) : '\u001B[49m';
   return `${fg}${bg}`;
 }

src/presentation/capabilities.ts

@@ -0,0 +1,15 @@
+/**
+ * Terminal color capability for NMSh-owned UI. Only explicit signals lower the
+ * level; without one NMSh keeps its truecolor behavior. Raw PTY output is never
+ * affected: this applies to colors NMSh itself emits.
+ */
+export type ColorLevel = 'none' | 'truecolor';
+
+export function colorLevel(env: NodeJS.ProcessEnv = process.env): ColorLevel {
+  const override = env.NMSH_COLOR?.toLowerCase();
+  if (override === '0' || override === 'none' || override === 'off') return 'none';
+  if (override === 'truecolor') return 'truecolor';
+  if (env.NO_COLOR) return 'none';
+  if (env.TERM === 'dumb') return 'none';
+  return 'truecolor';
+}

src/presentation/environment.ts

@@ -16,7 +16,16 @@ export function presentationCompletionTime(completedAt: Date): Date {
   return isDeterministicPresentation() ? presentationNow() : completedAt;
 }
 
-/** Stable shimmer phase for visual captures without changing measured durations. */
+/**
+ * True when NMSh-owned decorative motion should stay still: the user asked for
+ * reduced motion (NMSH_REDUCED_MOTION=1), or presentation is deterministic.
+ * Measured durations and shell behavior are never affected.
+ */
+export function isReducedMotion(): boolean {
+  return process.env.NMSH_REDUCED_MOTION === '1' || isDeterministicPresentation();
+}
+
+/** Stable shimmer/activity phase when motion is reduced, without changing measured durations. */
 export function presentationAnimationElapsed(elapsedMs: number): number {
-  return isDeterministicPresentation() ? 0 : elapsedMs;
+  return isReducedMotion() ? 0 : elapsedMs;
 }

src/ui/palette.ts

@@ -1,3 +1,5 @@
+import {colorLevel} from '../presentation/capabilities.js';
+
 export interface RgbColor {
   red: number;
   green: number;
@@ -26,10 +28,13 @@ export const UI_COLORS = {
   selection: {red: 88, green: 96, blue: 145},
 } as const satisfies Record<string, RgbColor>;
 
+/** Color escapes are empty when the terminal is not to be colored (NO_COLOR, TERM=dumb, NMSH_COLOR=none). */
 export function foreground(color: RgbColor): string {
+  if (colorLevel() === 'none') return '';
   return `\u001B[38;2;${color.red};${color.green};${color.blue}m`;
 }
 
 export function background(color: RgbColor): string {
+  if (colorLevel() === 'none') return '';
   return `\u001B[48;2;${color.red};${color.green};${color.blue}m`;
 }

tests/accessibilityBaseline.test.ts

@@ -0,0 +1,54 @@
+import assert from 'node:assert/strict';
+import test from 'node:test';
+import {colorLevel} from '../src/presentation/capabilities.js';
+import {isReducedMotion, presentationAnimationElapsed} from '../src/presentation/environment.js';
+import {background, foreground, UI_COLORS} from '../src/ui/palette.js';
+import {shimmerText} from '../src/status/shimmer.js';
+import {GLYPHS} from '../src/ui/glyphs.js';
+
+function withEnv<T>(patch: Record<string, string | undefined>, run: () => T): T {
+  const saved = Object.fromEntries(Object.keys(patch).map(name => [name, process.env[name]]));
+  for (const [name, value] of Object.entries(patch)) { if (value === undefined) delete process.env[name]; else process.env[name] = value; }
+  try { return run(); } finally {
+    for (const [name, value] of Object.entries(saved)) { if (value === undefined) delete process.env[name]; else process.env[name] = value; }
+  }
+}
+const CLEAN = {NO_COLOR: undefined, NMSH_COLOR: undefined, NMSH_REDUCED_MOTION: undefined, NMSH_DETERMINISTIC: undefined, TERM: 'xterm-256color'};
+
+test('color level only drops on explicit signals', () => {
+  assert.equal(colorLevel({TERM: 'xterm-256color'}), 'truecolor');
+  assert.equal(colorLevel({}), 'truecolor');
+  assert.equal(colorLevel({NO_COLOR: '1'}), 'none');
+  assert.equal(colorLevel({NO_COLOR: ''}), 'truecolor');
+  assert.equal(colorLevel({TERM: 'dumb'}), 'none');
+  assert.equal(colorLevel({NO_COLOR: '1', NMSH_COLOR: 'truecolor'}), 'truecolor');
+  assert.equal(colorLevel({NMSH_COLOR: 'none'}), 'none');
+});
+
+test('palette helpers emit no color escapes under NO_COLOR', () => {
+  withEnv({...CLEAN}, () => assert.match(foreground(UI_COLORS.accent), /^\u001B\[38;2;/u));
+  withEnv({...CLEAN, NO_COLOR: '1'}, () => {
+    assert.equal(foreground(UI_COLORS.accent), '');
+    assert.equal(background(UI_COLORS.accent), '');
+    assert.equal(shimmerText('Running ls', 500, false).includes('\u001B'), false);
+  });
+});
+
+test('status cues survive without color', () => {
+  withEnv({NMSH_ICONS: 'safe'}, () => {
+    assert.notEqual(GLYPHS.success, GLYPHS.failure);
+    assert.match(GLYPHS.success + GLYPHS.failure, /^[\x20-\x7e]+$/u);
+  });
+});
+
+test('reduced motion freezes the animation phase but not measured time', () => {
+  withEnv({...CLEAN}, () => {
+    assert.equal(isReducedMotion(), false);
+    assert.equal(presentationAnimationElapsed(4321), 4321);
+  });
+  withEnv({...CLEAN, NMSH_REDUCED_MOTION: '1'}, () => {
+    assert.equal(isReducedMotion(), true);
+    assert.equal(presentationAnimationElapsed(4321), 0);
+  });
+  withEnv({...CLEAN, NMSH_DETERMINISTIC: '1'}, () => assert.equal(isReducedMotion(), true));
+});