lab/ux
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

camera: previewRotationQuarterTurns + async previewSize event

Browse Source 
Black-screen + extra-90°-rotation on Android both came from
AVFoundation vs CameraX behaving differently at the preview output:

  - AVFoundation: data-output connection's `videoOrientation`
    pre-rotates sample buffers. The Flutter Texture displays them
    upright; `device.activeFormat` reports the sensor-native size
    synchronously.
  - CameraX: the SurfaceProvider hands back a Surface; CameraX
    writes raw sensor frames into it. Rotation is a *transform hint*
    via Preview.setTargetRotation that consumers must apply
    themselves. And the final negotiated resolution isn't known
    until the first SurfaceRequest fires — which happens AFTER
    bindToLifecycle, AFTER lifecycle.start, async on the camera
    executor. So `create` was returning Size(0,0).

Surface extension to bridge the gap:

  - UxCameraValue.previewRotationQuarterTurns (int 0/1/2/3).
    iOS native always emits 0; Android native emits
    `(sensorRotationDegrees / 90) % 4` for the active camera.
    [UxCameraPreview] wraps the Texture in a RotatedBox by that many
    quarter-turns (applied *before* the front-cam mirror so the
    flip lives in screen space, not sensor space).

  - UxCameraPreviewSizeChanged event. Android emits this from
    PreviewSink.onResize whenever a SurfaceRequest carries a new
    resolution; the controller copies it into value.previewSize.
    First emission is what unblocks the camera_thumb's SizedBox
    from its initial 0x0 = "render nothing" state.

  - UxCameraBackend.setDescription's return changed from `Size` to
    `({Size previewSize, int previewRotationQuarterTurns})` so
    a lens swap can both update the rotation and signal that a new
    previewSizeChanged event is incoming.

iOS continues to send previewSize in the create result (the active
format is known synchronously); no previewSizeChanged emission is
needed there. The new field is set to 0 in both create and
setDescription results on iOS.
This commit is contained in:
agra
2026-05-13 17:44:45 +03:00
parent a3020baeb9
commit cc243b7b0a
11 changed files with 141 additions and 20 deletions
Download Patch File Download Diff File Expand all files Collapse all files

23
android/src/main/kotlin/io/swipelab/ux/camera/CameraInstance.kt
View File

@@ -46,6 +46,19 @@ class CameraInstance(
val currentLens: String get() = lens
val audioClaimed: Boolean get() = enableAudio
/// Number of 90° CW rotations the Flutter Texture needs so the
/// sensor frames display upright on a portrait screen. Derived
/// from the active camera's `sensorRotationDegrees`.
val previewRotationQuarterTurns: Int get() {
val degrees = cameraProvider?.let {
val selector = if (lens == "front") CameraSelector.DEFAULT_FRONT_CAMERA
else CameraSelector.DEFAULT_BACK_CAMERA
selector.filter(it.availableCameraInfos).firstOrNull()
?.sensorRotationDegrees ?: 0
} ?: 0
return ((degrees % 360 + 360) % 360) / 90
}
/// Bind the provider against [lens]. Resolves the
/// [ProcessCameraProvider.getInstance] future on the main executor
/// before invoking [onReady]. [onReady] fires with success or the
@@ -59,6 +72,16 @@ class CameraInstance(
this.lens = lens
this.enableAudio = enableAudio
previewSink.onResize = { size ->
emit(mapOf(
"event" to "previewSizeChanged",
"previewSize" to mapOf(
"width" to size.width.toDouble(),
"height" to size.height.toDouble(),
),
))
}
val future = ProcessCameraProvider.getInstance(context)
future.addListener({
if (disposed) return@addListener

2
android/src/main/kotlin/io/swipelab/ux/camera/CameraPlugin.kt
View File

@@ -224,6 +224,7 @@ class CameraPlugin :
"width" to instance.previewSize.width.toDouble(),
"height" to instance.previewSize.height.toDouble(),
),
"previewRotationQuarterTurns" to instance.previewRotationQuarterTurns,
))
}
}
@@ -278,6 +279,7 @@ class CameraPlugin :
"width" to size.width.toDouble(),
"height" to size.height.toDouble(),
),
"previewRotationQuarterTurns" to instance.previewRotationQuarterTurns,
))
} catch (t: Throwable) {
if (oldLens != newLens) lensesInUse.remove(newLens)

9
android/src/main/kotlin/io/swipelab/ux/camera/PreviewSink.kt
View File

@@ -29,12 +29,21 @@ class PreviewSink(
var previewSize: android.util.Size = android.util.Size(0, 0)
private set
/// Fired every time CameraX hands us a [SurfaceRequest] with a
/// (possibly new) resolution. The [CameraInstance] forwards this
/// to Dart as a `previewSizeChanged` event so the controller's
/// `value.previewSize` updates after CameraX's first negotiation
/// (which lands after `create` has already returned).
var onResize: ((android.util.Size) -> Unit)? = null
/// `Preview.SurfaceProvider` callback. Pass directly to
/// `previewUseCase.setSurfaceProvider(sink::provideSurface)`.
fun provideSurface(request: SurfaceRequest) {
val res = request.resolution
surfaceTexture.setDefaultBufferSize(res.width, res.height)
val changed = res != previewSize
previewSize = res
if (changed) onResize?.invoke(res)
// Tear down any prior surface BEFORE handing out the new one —
// CameraX retains it until provideSurface's listener fires.

7
ios/Classes/Camera/CameraPlugin.swift
View File

@@ -136,7 +136,8 @@ public class CameraPlugin: NSObject, NativePlugin, FlutterStreamHandler {
"previewSize": [
"width": size.width,
"height": size.height,
]
],
"previewRotationQuarterTurns": 0,
])
}
} catch let error as NSError {
@@ -344,6 +345,10 @@ public class CameraPlugin: NSObject, NativePlugin, FlutterStreamHandler {
"width": size.width,
"height": size.height,
],
// iOS pre-rotates frames via the data-output
// connection's videoOrientation, so the Flutter
// Texture displays upright as-is.
"previewRotationQuarterTurns": 0,
])
}
} catch let error as NSError {

25
lib/src/camera/camera.dart
View File

@@ -71,6 +71,7 @@ class UxCameraValue {
this.deviceOrientation = DeviceOrientation.portraitUp,
this.enableAudio = false,
this.audioPermissionGranted = false,
this.previewRotationQuarterTurns = 0,
this.errorDescription,
});
@@ -103,6 +104,16 @@ class UxCameraValue {
/// no audio track and callers should surface a hint.
final bool audioPermissionGranted;
/// Number of 90° clockwise rotations the preview Texture needs so
/// the sensor frames display upright. On iOS the data output
/// pre-rotates via `AVCaptureConnection.videoOrientation` and this
/// is always 0. On Android CameraX delivers sensor-native frames to
/// the Surface and the consumer rotates — typically 1 for
/// `sensorOrientation: 90` back cams and 3 for `sensorOrientation:
/// 270` front cams. Applied inside [UxCameraPreview]; consumers
/// don't read this directly.
final int previewRotationQuarterTurns;
/// Set to the last native session error's message when one fires.
/// Cleared on the next successful state transition.
final String? errorDescription;
@@ -117,6 +128,7 @@ class UxCameraValue {
DeviceOrientation? deviceOrientation,
bool? enableAudio,
bool? audioPermissionGranted,
int? previewRotationQuarterTurns,
Object? errorDescription = _unset,
}) =>
UxCameraValue(
@@ -127,6 +139,8 @@ class UxCameraValue {
deviceOrientation: deviceOrientation ?? this.deviceOrientation,
enableAudio: enableAudio ?? this.enableAudio,
audioPermissionGranted: audioPermissionGranted ?? this.audioPermissionGranted,
previewRotationQuarterTurns:
previewRotationQuarterTurns ?? this.previewRotationQuarterTurns,
errorDescription: identical(errorDescription, _unset)
? this.errorDescription
: errorDescription as String?,
@@ -211,6 +225,7 @@ class UxCameraController extends ValueNotifier<UxCameraValue> {
value = value.copyWith(
isInitialized: true,
previewSize: result.previewSize,
previewRotationQuarterTurns: result.previewRotationQuarterTurns,
audioPermissionGranted: audioGranted,
);
} catch (_) {
@@ -235,6 +250,8 @@ class UxCameraController extends ValueNotifier<UxCameraValue> {
break;
case UxCameraDiagnostic(:final message):
_log.i('recorder: $message');
case UxCameraPreviewSizeChanged(:final previewSize):
value = value.copyWith(previewSize: previewSize);
}
}
@@ -257,8 +274,12 @@ class UxCameraController extends ValueNotifier<UxCameraValue> {
/// recording is in flight — call [stopVideoRecording] first.
Future<void> setDescription(UxCameraDescription description) async {
final handle = _requireHandle('setDescription');
final size = await UxCameraBackend.instance.setDescription(handle, description.id);
value = value.copyWith(description: description, previewSize: size);
final r = await UxCameraBackend.instance.setDescription(handle, description.id);
value = value.copyWith(
description: description,
previewSize: r.previewSize,
previewRotationQuarterTurns: r.previewRotationQuarterTurns,
);
}
Future<void> setFlashMode(UxFlashMode mode) async {

29
lib/src/camera/camera_backend.dart
View File

@@ -47,8 +47,13 @@ abstract class UxCameraBackend {
Future<void> disposeInstance(int handle);
/// Swap to a different camera mid-session. Resets the lock and clears
/// any pending recording. Returns the new preview size.
Future<Size> setDescription(int handle, String cameraId);
/// any pending recording. Returns the new preview size and rotation;
/// the size may again be `Size.zero` initially on Android, with a
/// follow-up [UxCameraPreviewSizeChanged] event.
Future<({Size previewSize, int previewRotationQuarterTurns})> setDescription(
int handle,
String cameraId,
);
/// Set the flash mode used for the next [takePicture]. On front cameras
/// without a screen-flash fallback the backend silently no-ops; the
@@ -104,11 +109,21 @@ class UxCameraCreateResult {
required this.handle,
required this.textureId,
required this.previewSize,
this.previewRotationQuarterTurns = 0,
});
final int handle;
final int textureId;
/// Initial preview size; may be `Size.zero` when the native side
/// can't determine it synchronously (Android CameraX needs the
/// first `SurfaceRequest` to fire before it knows). In that case
/// a [UxCameraPreviewSizeChanged] event follows.
final Size previewSize;
/// Number of 90° CW rotations the Texture widget needs. iOS: 0.
/// Android: derived from the selected camera's sensor orientation.
final int previewRotationQuarterTurns;
}
/// Events pushed by the native side over `ux/camera/events`. Sealed —
@@ -138,6 +153,16 @@ class UxCameraSessionResumed extends UxCameraEvent {
const UxCameraSessionResumed(super.handle);
}
/// Fired when the native side learns or revises the preview's pixel
/// dimensions. Android emits this after CameraX's first
/// `SurfaceRequest` resolves (the size isn't known at `create` time);
/// iOS doesn't emit it (the size lands in the `create` result
/// synchronously from `device.activeFormat`).
class UxCameraPreviewSizeChanged extends UxCameraEvent {
const UxCameraPreviewSizeChanged(super.handle, this.previewSize);
final Size previewSize;
}
/// Free-text diagnostic message from the native recorder. Routed by
/// the controller to `Log.tag('camera').i(...)` so it lands in the
/// log_server pipeline (`~/banlu/tools/log_server/data/banlu.jsonl`).

26
lib/src/camera/camera_channel.dart
View File

@@ -58,6 +58,8 @@ class MethodChannelUxCameraBackend implements UxCameraBackend {
(size['width'] as num).toDouble(),
(size['height'] as num).toDouble(),
),
previewRotationQuarterTurns:
(m['previewRotationQuarterTurns'] as num?)?.toInt() ?? 0,
);
}
@@ -70,15 +72,22 @@ class MethodChannelUxCameraBackend implements UxCameraBackend {
_invokeVoid('dispose', {'handle': handle});
@override
Future<Size> setDescription(int handle, String cameraId) async {
Future<({Size previewSize, int previewRotationQuarterTurns})> setDescription(
int handle,
String cameraId,
) async {
final m = await _invokeMap('setDescription', {
'handle': handle,
'cameraId': cameraId,
});
final s = (m['previewSize'] as Map).cast<Object?, Object?>();
return Size(
(s['width'] as num).toDouble(),
(s['height'] as num).toDouble(),
return (
previewSize: Size(
(s['width'] as num).toDouble(),
(s['height'] as num).toDouble(),
),
previewRotationQuarterTurns:
(m['previewRotationQuarterTurns'] as num?)?.toInt() ?? 0,
);
}
@@ -173,6 +182,15 @@ class MethodChannelUxCameraBackend implements UxCameraBackend {
handle,
m['message'] as String? ?? '',
);
case 'previewSizeChanged':
final s = (m['previewSize'] as Map).cast<Object?, Object?>();
return UxCameraPreviewSizeChanged(
handle,
Size(
(s['width'] as num).toDouble(),
(s['height'] as num).toDouble(),
),
);
default:
return UxCameraSessionError(handle, 'unknown_event', null);
}

17
lib/src/camera/camera_preview.dart
View File

@@ -27,11 +27,18 @@ class UxCameraPreview extends StatelessWidget {
builder: (context, value, _) {
final id = controller.textureId;
if (id == null) return SizedBox.expand();
final mirror = value.description.lens == UxCameraLens.front;
final texture = Texture(textureId: id);
return mirror
? Transform.flip(flipX: true, child: texture)
: texture;
Widget child = Texture(textureId: id);
// Order matters: rotate first (sensor → screen frame), then
// mirror in screen space. Reversing them would mirror across
// an axis that's still aligned with the sensor.
final turns = value.previewRotationQuarterTurns;
if (turns != 0) {
child = RotatedBox(quarterTurns: turns, child: child);
}
if (value.description.lens == UxCameraLens.front) {
child = Transform.flip(flipX: true, child: child);
}
return child;
},
);
}

13
lib/src/testing/fake_camera.dart
View File

@@ -148,9 +148,18 @@ class FakeUxCameraBackend implements UxCameraBackend {
}
@override
Future<Size> setDescription(int handle, String cameraId) async {
Future<({Size previewSize, int previewRotationQuarterTurns})> setDescription(
int handle,
String cameraId,
) async {
setDescriptionCalls.add((handle: handle, cameraId: cameraId));
return previewSize;
return (previewSize: previewSize, previewRotationQuarterTurns: 0);
}
/// Push a `previewSizeChanged` event for [handle]. Tests that need
/// to simulate Android's async preview-size resolve drive this.
void emitPreviewSizeChanged(int handle, Size size) {
_controllerFor(handle).add(UxCameraPreviewSizeChanged(handle, size));
}
@override

2
lib/ux.dart
View File

@@ -9,7 +9,7 @@ export 'src/bend_box.dart';
export 'src/json_extension.dart';
export 'src/bezier.dart';
export 'src/camera/camera.dart';
export 'src/camera/camera_backend.dart' show UxCameraBackend, UxCameraCreateResult, UxCameraEvent, UxCameraDeviceOrientationChanged, UxCameraSessionError, UxCameraSessionInterrupted, UxCameraSessionResumed, UxCameraDiagnostic;
export 'src/camera/camera_backend.dart' show UxCameraBackend, UxCameraCreateResult, UxCameraEvent, UxCameraDeviceOrientationChanged, UxCameraSessionError, UxCameraSessionInterrupted, UxCameraSessionResumed, UxCameraDiagnostic, UxCameraPreviewSizeChanged;
export 'src/camera/camera_channel.dart' show MethodChannelUxCameraBackend;
export 'src/camera/camera_preview.dart';
export 'src/clipboard.dart';

8
test/camera/camera_channel_test.dart
View File

@@ -81,16 +81,18 @@ void main() {
expect(calls.every((c) => (c.arguments as Map)['handle'] == 11), isTrue);
});
test('setDescription returns the new previewSize', () async {
test('setDescription returns previewSize + rotation', () async {
handle((_) => {
'previewSize': {'width': 1280, 'height': 720},
'previewRotationQuarterTurns': 1,
});
final size = await backend.setDescription(7, 'next');
final r = await backend.setDescription(7, 'next');
expect(calls.single.method, 'setDescription');
expect(calls.single.arguments, {'handle': 7, 'cameraId': 'next'});
expect(size, const Size(1280, 720));
expect(r.previewSize, const Size(1280, 720));
expect(r.previewRotationQuarterTurns, 1);
});
test('setFlashMode encodes the enum', () async {