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fix(ios): sync preview orientation with device orientation #86

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fix(ios): sync preview orientation with device orientation #86

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fix(ios): sync preview orientation with device orientation 
The AVCaptureVideoPreviewLayer connection orientation is never synced
with the device orientation, causing the camera preview to appear
rotated 90 degrees when the device is in landscape mode (e.g. iPad).

Add _syncPreviewOrientation() which reads the current interface
orientation from UIWindowScene and applies it to the preview layer
connection using videoRotationAngle (iOS 17+) or the deprecated
videoOrientation fallback. The sync is called on load, on orientation
change, and after toggleCamera().
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@grfalk
grfalk committed Apr 5, 2026
commit bf0eb5ffd37ee84f1dd314f77647c2c087369463
37 changes: 36 additions & 1 deletion packages/mlkit-core/index.ios.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -27,7 +27,7 @@ import {
boundingBoxSettingsProperty,
DEFAULT_BOUNDING_BOX_SETTINGS,
} from './common';
import { Color, File, ImageSource, Utils } from '@nativescript/core';
import { Application, Color, File, ImageSource, Utils } from '@nativescript/core';
import lazy from '@nativescript/core/utils/lazy';
import { DetectionEvent, StillImageDetectionOptions } from '.';

Expand Down Expand Up @@ -108,6 +108,7 @@ export class MLKitView extends MLKitViewBase {

_mlkitHelper: TNSMLKitHelper;
_onScanCallback: (result: any, type) => void;
_orientationHandler: () => void;

constructor() {
super();
Expand Down Expand Up @@ -509,9 +510,17 @@ export class MLKitView extends MLKitViewBase {
onLoaded() {
super.onLoaded();
this.startPreview();
this._syncPreviewOrientation();

this._orientationHandler = () => this._syncPreviewOrientation();
Application.on('orientationChanged', this._orientationHandler);
}

onUnloaded() {
if (this._orientationHandler) {
Application.off('orientationChanged', this._orientationHandler);
this._orientationHandler = null;
}
this.stopPreview();
super.onUnloaded();
}
Expand All @@ -520,8 +529,34 @@ export class MLKitView extends MLKitViewBase {
this._mlkitHelper.stopPreview();
}

private _syncPreviewOrientation(): void {
if (!this._preview) return;

// The capture session connection may not be established immediately
// after startPreview(); defer to allow the session to start.
setTimeout(() => {
const conn = this._preview?.connection;
if (!conn) return;

const windowScene = UIApplication.sharedApplication.connectedScenes?.allObjects?.firstObject;
if (!windowScene || !(windowScene instanceof UIWindowScene)) return;
const orientation = (windowScene as UIWindowScene).interfaceOrientation;
if (orientation < 1 || orientation > 4) return;

// iOS 17+ uses videoRotationAngle (degrees); older versions use
// the deprecated videoOrientation enum.
if (typeof conn.videoRotationAngle !== 'undefined') {
const angleMap = { 1: 90, 2: 270, 3: 0, 4: 180 };
conn.videoRotationAngle = angleMap[orientation] ?? 90;
} else {
conn.videoOrientation = orientation;
}
}, 100);
}

public toggleCamera(): void {
this._mlkitHelper.toggleCamera();
this._syncPreviewOrientation();
}

public startPreview(): void {
Expand Down