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camera: app-lifecycle pause / resume (Phase 6 polish)

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Camera page kept the session running while the host app was
backgrounded — wastes battery, holds the hardware, and blocks
other apps from grabbing the camera. Add per-platform observers
that pause/resume the session on app foreground/background, with
a uniform `pauseForBackground` / `resumeForForeground` pair on the
shared CameraInstance.

Behaviour:
  - On background: any in-flight recording is hard-cancelled
    (matches every messaging app — the take ends with the app
    switch). The session stops so the OS can release the camera.
  - On foreground: session restarts iff it had been running.
    Emits `sessionInterrupted` (`reason: appBackgrounded`) and
    `sessionResumed` events so the Dart side can surface UX
    affordances if needed.

iOS — `ios/Classes/Camera/CameraInstance+iOS.swift`:
  Subscribes to UIApplication.{willResignActive, didBecomeActive}
  notifications. Work hops onto sessionQueue so AV mutations stay
  serialised. Storage uses the shared
  `CameraInstance.lifecycleCleanup` closure slot — extension
  doesn't need to add stored properties.

Android — added `androidx.lifecycle:lifecycle-process:2.7.0`,
  observes `ProcessLifecycleOwner.get().lifecycle`. ON_STOP →
  `pauseForBackground` (cancels recording + drops
  CustomLifecycleOwner to CREATED → CameraX releases camera).
  ON_START → `resumeForForeground`. Observer add/remove on main
  thread per `ProcessLifecycleOwner` contract.

macOS — `macos/Classes/Camera/CameraInstance+macOS.swift`:
  Intentional no-op. macOS desktop background semantics are
  softer; the chat composer's Card dialog typically stays
  foregrounded. Slot is wired so the shared
  `observeLifecycle()` call still compiles.

Verified: all four platforms (iOS / Android / macOS / app tests)
build clean. Pod install picks up the new iOS extension file
once Pods/ is fresh — `flutter clean` if mid-iteration.
This commit is contained in:
agra
2026-05-13 21:43:50 +03:00
parent 71c84179a6
commit 3d36f17edf
5 changed files with 178 additions and 0 deletions
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macos/Classes/Camera/CameraInstance+macOS.swift Normal file
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import Foundation
/// macOS counterpart of `CameraInstance+iOS.swift`.
///
/// macOS doesn't have iOS's hard "the app is backgrounded, you must
/// release the camera" lifecycle. A backgrounded Mac app keeps
/// running, and there's no equivalent UIApplication notification —
/// the closest analogues are `NSApplication.didResignActive` /
/// `…didBecomeActive`, but the chat composer's macOS surface (a
/// Card dialog) typically stays in the foreground long enough that
/// teardown on resign-active would cost more than it saves.
///
/// Left as a no-op so the shared `CameraInstance.observeLifecycle()`
/// call compiles. If a need surfaces later, wire NSApplication
/// observers here calling `pauseForBackground` / `resumeForForeground`.
extension CameraInstance {
func observeLifecycle() {
// Intentionally empty.
}
}