posture-aware Activity orientation and landscape PreviewDisplay framing - #650

Stacked PR: Based on main

Summary

Establishes the orientation and viewfinder-framing foundation for Adaptive Capture across multi-window panes, foldables, and tablets. Replaces MainActivity's static android:screenOrientation="nosensor" manifest lock with a posture-aware runtime policy (NOSENSOR on full-screen < 600dp handhelds; UNSPECIFIED in multi-window or >= 600dp large screens) and upgrades PreviewDisplay to frame wide containers in landscape aspect ratios (4:3 / 16:9), run in a single layout pass without BoxWithConstraints subcomposition, isolate optical coordinates from RTL mirroring, and support keyboard/TalkBack center-focus activation.

Key Changes

• Activity Orientation & Config-Change Contract (AndroidManifest.xml, MainActivity.kt):
  • Removes static android:screenOrientation="nosensor" and declares android:configChanges="orientation|screenSize|smallestScreenSize|screenLayout|keyboardHidden" so rotations, multi-window resizes, and fold/unfold transitions do not recreate MainActivity (allowing active video recordings to continue across a foldable unfold).
  • Adds resolveRequestedOrientation(isInMultiWindowMode, smallestScreenWidthDp) (600dp threshold) wired across onCreate, addOnMultiWindowModeChangedListener, and onConfigurationChanged.
• Adaptive Viewfinder Framing & Layout (CaptureScreenComponents.kt, CaptureScaffold.kt):
  • Extracts calculateViewfinderSize(...) to fit AspectRatio.toLandscapeFloat() when useLandscapeAspectRatio && maxWidth > maxHeight (preserving portrait ratios when maxWidth <= maxHeight and returning DpSize.Zero for non-positive bounds).
  • Adds contentAlignment: Alignment = Alignment.TopCenter and useLandscapeAspectRatio: Boolean = false to PreviewDisplay, and enables useLandscapeAspectRatio = true in CaptureScaffold.
  • Replaces BoxWithConstraints (SubcomposeLayout) with a standard Box + single-pass Modifier.layout reporting ViewfinderTopLine, and moves capture-blink alpha + 16.dp corner clipping into draw-phase Modifier.graphicsLayer.
• Accessibility, Keyboard Focus & Gesture Hygiene (CaptureScreenComponents.kt, strings.xml):
  • Wraps the inner viewfinder subtree in LocalLayoutDirection provides LayoutDirection.Ltr.
  • Adds OnClick ("Focus center"), .focusable, and hardware key activation (Enter, NumPadEnter, DirectionCenter, Spacebar) gated on >= 48.dp interactive bounds, plus accessible Indeterminate loading semantics.

Technical Notes

• Orientation Policy Invariant: Full-screen compact handhelds (!isInMultiWindowMode && smallestScreenWidthDp < 600) stay on SCREEN_ORIENTATION_NOSENSOR so UI chrome can counter-rotate smoothly via sensor gravity without OS window-rotation animations. Multi-window panes and sw >= 600dp devices use SCREEN_ORIENTATION_UNSPECIFIED to prevent 1:1 OS compatibility letterboxing.
• Single-Pass Measurement & ViewfinderTopLine: Measuring downstream modifiers (PREVIEW_DISPLAY, onGloballyPositioned for LocalOverlapTargetBounds, transformable, graphicsLayer) with Constraints.fixed(widthPx, heightPx) inside Modifier.layout guarantees overlap bounds and rounded-corner clipping track the exact visible frame while propagating ViewfinderTopLine upward through the outer Box.
• Optical LTR Isolation: CameraXViewfinder and MutableCoordinateTransformer always emit top-left physical coordinates; forcing LayoutDirection.Ltr inside PreviewDisplay keeps FocusMeteringIndicator's Modifier.offset aligned with physical tap points while preserving ambient RTL outside the viewfinder.

Bugs Fixed Along the Way

• RTL Focus Reticle Mirroring: Fixed FocusMeteringIndicator rendering horizontally mirrored away from the physical tap point under LayoutDirection.Rtl.
• Stale Gesture Callback Closures: Fixed pointerInput(onFlipCamera) capturing stale onTapToFocus lambdas (and restarting mid-gesture on onFlipCamera updates) and rememberTransformableState capturing stale onScaleZoom lambdas; migrated to the non-deprecated 4-parameter rememberTransformableState overload.
• Capture Blink Cancellation Freeze & Reduced-Motion Strobe: Added try/finally around delay(BLINK_TIME) so cancelled blink coroutines cannot leave PreviewDisplay stuck at alpha = 0f, suppressed zero-alpha strobing when LocalDisableAnimations is true, and eliminated per-frame blink recompositions.
• Zero-Bounds NaN & Loading Spinner Hang: Guarded maxWidth <= 0.dp || maxHeight <= 0.dp against NaN division and switched the loading indicator to a static 0.75f progress arc when LocalDisableAnimations is true while exposing R.string.camera_not_ready semantics.

Not Included Yet

• Comes later in this series:
  • Live Preview.targetRotation and sensor-aligned ViewPort sync (kim/adaptive/viewfinder-rotation).
  • Orientation lock during active video recording (kim/adaptive/debug-layout-readout, PR add 3-signal rotation, recording lock, and debug layout readout #643).
  • Centered adaptive posture layouts and compact counter-rotation (kim/adaptive/layouts -> kim/adaptive/layout-rotation).
• Open follow-ups:
  • Hardening recording across unfold: ✨ Recording now continues across unfold on both cameras ✨ ; one non-reproducible front-camera freeze was seen in manual testing, so this path needs broader device testing and automated coverage.
  • Portrait split-screen panes on landscape displays (W < H at windowRotation = 90°/270°): PreviewDisplay currently picks 3:4 vs. 4:3 from pane bounds rather than oriented stream dimensions, center-cropping ~44% (4:3) to ~68% (16:9) of horizontal FOV relative to the saved photo; follow-up will drive framing from SurfaceRequest dimensions/rotation so narrow panes letterbox cleanly (100% WYSIWYG).

Testing

• ./gradlew :app:testDebugUnitTest --tests "*MainActivityOrientationTest" — 3 unit tests covering compact full-screen (411dp, 599dp), compact multi-window, and large-screen/foldable (600dp, 673dp) orientation policies.
• ./gradlew :ui:components:capture:testDebugUnitTest --tests "*PreviewDisplayTest" — 15 Robolectric unit & Compose UI tests covering calculateViewfinderSize across phone/tablet/foldable/zero-bound geometries, dynamic 4:3 ↔ 16:9 pillarbox/letterbox overlap bounds, LTR vs. RTL tap-to-focus parity, rememberUpdatedState callback refresh + pinch zoom, keyboard/TalkBack center-focus & < 48dp gating, and frame-by-frame capture blink alpha.
• ./gradlew :ui:components:capture:connectedDebugAndroidTest -Pandroid.testInstrumentationRunnerArguments.class=com.google.jetpackcamera.ui.components.capture.CaptureScreenComponentsTest — 3 Espresso AccessibilityValidator tests covering dark/light loading states and live SurfaceRequest center-focus semantics.