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2026-04-18 23:11:35 +02:00
commit f7cfd2a86e
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+// Screen-share quality presets modelled on Discord's tiers. Values are the
+// upper bounds — LiveKit + WebRTC's congestion control dynamically drop to
+// lower spatial/temporal layers (SVC with VP9) when the uplink degrades, so
+// these numbers behave as "up to" caps, not constant bitrates.
+
+const STORAGE_KEY = 'chatapp.screenshare';
+
+export type ScreenSharePreset =
+  | 'auto'
+  | '720p30'
+  | '720p60'
+  | '1080p30'
+  | '1080p60'
+  | '1440p60'
+  | '4k60';
+
+export interface ScreenShareSettings {
+  preset: ScreenSharePreset;
+}
+
+const DEFAULTS: ScreenShareSettings = {
+  preset: 'auto',
+};
+
+export interface PresetParams {
+  dims: { width: number; height: number } | null; // null = browser picks native
+  framerate: number;
+  bitrateKbps: number;
+  label: string;
+}
+
+const PRESET_PARAMS: Record<ScreenSharePreset, PresetParams> = {
+  auto: { dims: null, framerate: 60, bitrateKbps: 8000, label: 'Auto (Original)' },
+  '720p30': {
+    dims: { width: 1280, height: 720 },
+    framerate: 30,
+    bitrateKbps: 2500,
+    label: '720p · 30 fps',
+  },
+  '720p60': {
+    dims: { width: 1280, height: 720 },
+    framerate: 60,
+    bitrateKbps: 3500,
+    label: '720p · 60 fps',
+  },
+  '1080p30': {
+    dims: { width: 1920, height: 1080 },
+    framerate: 30,
+    bitrateKbps: 4000,
+    label: '1080p · 30 fps',
+  },
+  '1080p60': {
+    dims: { width: 1920, height: 1080 },
+    framerate: 60,
+    bitrateKbps: 6000,
+    label: '1080p · 60 fps',
+  },
+  '1440p60': {
+    dims: { width: 2560, height: 1440 },
+    framerate: 60,
+    bitrateKbps: 8000,
+    label: '1440p · 60 fps',
+  },
+  '4k60': {
+    dims: { width: 3840, height: 2160 },
+    framerate: 60,
+    bitrateKbps: 10_000,
+    label: '4K · 60 fps',
+  },
+};
+
+export const PRESET_ORDER: ReadonlyArray<ScreenSharePreset> = [
+  'auto',
+  '720p30',
+  '720p60',
+  '1080p30',
+  '1080p60',
+  '1440p60',
+  '4k60',
+];
+
+export function getPresetParams(p: ScreenSharePreset): PresetParams {
+  return PRESET_PARAMS[p];
+}
+
+type Listener = (s: ScreenShareSettings) => void;
+const listeners = new Set<Listener>();
+
+let cached: ScreenShareSettings | null = null;
+
+function isPreset(v: unknown): v is ScreenSharePreset {
+  return typeof v === 'string' && v in PRESET_PARAMS;
+}
+
+function read(): ScreenShareSettings {
+  if (cached) return cached;
+  try {
+    const raw = window.localStorage.getItem(STORAGE_KEY);
+    if (!raw) {
+      cached = DEFAULTS;
+      return cached;
+    }
+    const parsed = JSON.parse(raw) as Partial<ScreenShareSettings>;
+    cached = {
+      preset: isPreset(parsed.preset) ? parsed.preset : DEFAULTS.preset,
+    };
+    return cached;
+  } catch {
+    cached = DEFAULTS;
+    return cached;
+  }
+}
+
+function write(s: ScreenShareSettings): void {
+  cached = s;
+  try {
+    window.localStorage.setItem(STORAGE_KEY, JSON.stringify(s));
+  } catch {
+    /* quota / private mode */
+  }
+  for (const l of listeners) l(s);
+}
+
+export function getScreenShareSettings(): ScreenShareSettings {
+  return read();
+}
+
+export function updateScreenShareSettings(
+  patch: Partial<ScreenShareSettings>,
+): ScreenShareSettings {
+  const next = { ...read(), ...patch };
+  write(next);
+  return next;
+}
+
+export function subscribeScreenShareSettings(listener: Listener): () => void {
+  listeners.add(listener);
+  return () => listeners.delete(listener);
+}