Implement dual output for camera using QVideoWidget and QVideoSink, add camera permission handling, and enhance overlay error messaging

notes/02-mvp-mac-plan.md

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+# Plan — macOS fix + QVideoWidget + QVideoSink dual output
+
+## Cel
+
+Przywrócić działanie kamery na macOS (Elgato) przez:
+1. Przejście z manualnego `QPainter` renderowania na natywny `QVideoWidget`
+2. Dodanie `QVideoSink` jako drugiego wyjścia (frame access dla telemetrii)
+3. Obsługa `QCameraPermission` (Qt 6.5+)
+4. Dokumentacja packagingu przez `pyside6-deploy` na macOS
+
+## Kolejność implementacji
+
+### 1. camera/service.py
+
+```python
+class CameraService(QObject):
+    error_occurred = Signal(str)
+
+    def __init__(self, parent=None):
+        super().__init__(parent)
+        self._session = QMediaCaptureSession()
+        self._camera: QCamera | None = None
+
+    def set_video_widget(self, widget: QVideoWidget) -> None:
+        self._session.setVideoOutput(widget)
+
+    def set_video_sink(self, sink: QVideoSink) -> None:
+        self._session.setVideoSink(sink)
+
+    @property
+    def session(self) -> QMediaCaptureSession:
+        return self._session
+
+    @staticmethod
+    def available_cameras() -> list[QCameraDevice]:
+        return QMediaDevices.videoInputs()
+
+    def is_active(self) -> bool:
+        return self._camera is not None and self._camera.isActive()
+
+    def start(self, device: QCameraDevice) -> None:
+        self.stop()
+        self._camera = QCamera(device, self)
+        self._camera.errorOccurred.connect(self._on_error)
+        self._session.setCamera(self._camera)
+        self._camera.start()
+
+    def stop(self) -> None:
+        if self._camera is not None:
+            self._camera.stop()
+            self._session.setCamera(None)
+            self._camera.deleteLater()
+            self._camera = None
+
+    def set_camera_format(self, fmt: QCameraFormat) -> None:
+        if self._camera is not None:
+            self._camera.setCameraFormat(fmt)
+
+    def _on_error(self, error, error_string):
+        self.error_occurred.emit(error_string)
+```
+
+Zmiany:
+- Usunięto `self._sink` z `__init__`
+- Usunięto `self._session.setVideoOutput(self._sink)`
+- Dodano `set_video_widget(widget)` → `session.setVideoOutput(widget)`
+- Dodano `set_video_sink(sink)` → `session.setVideoSink(sink)`
+
+### 2. rendering/video_widget.py
+
+```python
+from __future__ import annotations
+
+from PySide6.QtMultimediaWidgets import QVideoWidget
+
+
+class VideoWidget(QVideoWidget):
+    def __init__(self, parent=None):
+        super().__init__(parent)
+        self.setMinimumSize(320, 240)
+```
+
+Zmiany:
+- Dziedziczy po `QVideoWidget` zamiast `QWidget`
+- Usunięto `on_frame(frame)` — nie potrzeba, renderowanie natywne
+- Usunięto `paintEvent` — nie potrzeba, robi to Qt
+- Usunięto `QImage`, `QPainter`, `SmoothPixmapTransform`
+
+### 3. rendering/overlay.py
+
+```python
+font = QFont("monospace", 11)  # zamiast "Consolas"
+```
+
+Dodatkowo: obsługa błędu w `paintEvent`:
+- Jeśli `self._metrics` ma klucz `"error"` → pomiń normalne metryki, narysuj czerwony komunikat błędu
+- Użyj `QColor(180, 40, 40)` zamiast zielonego
+
+### 4. app.py — nowe DI wiring
+
+```python
+def main():
+    app = QApplication(sys.argv)
+    app.setApplicationName("Duck Preview")
+
+    camera = CameraService()
+    video_sink = QVideoSink()
+    dispatcher = FrameDispatcher()
+    telemetry = TelemetryCollector()
+    video_widget = VideoWidget()
+    overlay = OverlayWidget()
+
+    camera.set_video_widget(video_widget)
+    camera.set_video_sink(video_sink)
+
+    video_sink.videoFrameChanged.connect(dispatcher.on_frame)
+    dispatcher.subscribe(telemetry.on_frame)
+
+    window = MainWindow(camera, video_widget, overlay)
+
+    # Wire error → overlay
+    camera.error_occurred.connect(
+        lambda msg: overlay.set_metrics({"error": msg})
+    )
+
+    # Poll telemetry → overlay
+    metrics_timer = QTimer()
+    metrics_timer.timeout.connect(
+        lambda: overlay.set_metrics(telemetry.metrics())
+    )
+    metrics_timer.start(200)
+
+    window.show()
+    sys.exit(app.exec())
+```
+
+Zmiany:
+- Tworzy `QVideoSink` jawnie
+- `camera.set_video_widget(video_widget)` + `camera.set_video_sink(video_sink)`
+- `video_sink.videoFrameChanged → dispatcher.on_frame`
+- Usunięto `camera.sink` (property nie istnieje)
+- `camera.error_occurred → overlay.set_metrics({"error": msg})`
+
+### 5. main_window.py — permission flow
+
+```python
+# Importy
+from PySide6.QtCore import QCameraPermission, Qt
+from PySide6.QtWidgets import QApplication
+
+# W _on_camera_selected:
+def _on_camera_selected(self, device: QCameraDevice) -> None:
+    self._request_camera_permission(device)
+
+def _request_camera_permission(self, device: QCameraDevice) -> None:
+    perm = QCameraPermission()
+    match QApplication.checkPermission(perm):
+        case Qt.PermissionStatus.Undetermined:
+            QApplication.requestPermission(perm, self,
+                lambda: self._request_camera_permission(device))
+        case Qt.PermissionStatus.Denied:
+            self._overlay.set_metrics({
+                "error": "Camera permission denied.\n"
+                         "Grant access in System Settings > "
+                         "Privacy & Security > Camera"
+            })
+        case Qt.PermissionStatus.Granted:
+            self._camera.start(device)
+            self._rebuild_resolution_menu(device)
+```
+
+### 6. pyside6-deploy.toml
+
+```toml
+[app]
+script = "duck_preview/__main__.py"
+name = "Duck Preview"
+bundle_identifier = "com.bartool.duck-preview"
+categories = "public.app-category.photography"
+platforms = ["macos"]
+```
+
+### 7. Po zmianach
+
+- `ruff check .` — czysty
+- `ruff format .` — sformatowany
+- `pytest -q` — 5 passed
+
+---
+
+## Podsumowanie architektury końcowej
+
+```
+CameraService
+  ├─ session.setVideoOutput(VideoWidget)   → natywne GPU rendering
+  └─ session.setVideoSink(VideoSink)       → frame access
+                                              └─ videoFrameChanged
+                                                   → FrameDispatcher
+                                                        ├─ TelemetryCollector
+                                                        └─ [future AI]
+
+MainWindow
+  ├─ _on_camera_selected
+  │    → QCameraPermission check (Undetermined/Denied/Granted)
+  │    → CameraService.start(device)
+  ├─ error_occurred → OverlayWidget.set_metrics({"error": ...})
+  └─ QTimer 200ms → TelemetryCollector.metrics() → OverlayWidget
+
+OverlayWidget
+  ├─ normal: zielone metryki (FPS, frame time, frame count)
+  └─ error: czerwony komunikat (np. brak permisji)
+```