android: lock portrait - UI composition glued to phone frame (top/bottom bars + image area absolutely fixed)

android/app/src/main/AndroidManifest.xml

@@ -16,7 +16,7 @@
         <activity
             android:name=".MainActivity"
             android:exported="true"
-            android:screenOrientation="fullSensor"
+            android:screenOrientation="portrait"
             android:configChanges="orientation|screenSize|screenLayout|keyboardHidden|uiMode"
             android:resizeableActivity="true">
             <intent-filter>

android/app/src/main/kotlin/com/mag160c/thermal/ui/AppRoot.kt

@@ -36,9 +36,10 @@ private val TABS = listOf(
 )
 
 /**
- * App shell.  The bottom navigation bar is always at the bottom in both
- * orientations (top/bottom bars keep their positions; only their inner
- * icons/text follow the screen).  Tab content lives in a stable slot.
+ * App shell.  The activity is portrait-locked, so the bottom navigation bar
+ * is glued to the phone's portrait bottom edge at all times (its absolute
+ * position never moves, however the phone is physically held).  Tab content
+ * lives in a stable slot.
  */
 @Composable
 fun AppRoot() {
@@ -58,7 +59,7 @@ fun AppRoot() {
             }
         }
 
-        // bottom navigation overlay (both orientations)
+        // bottom navigation overlay (glued to the portrait bottom edge)
         Surface(
             color = MaterialTheme.colorScheme.surface,
             modifier = Modifier

android/app/src/main/kotlin/com/mag160c/thermal/ui/UiInsets.kt

@@ -2,7 +2,7 @@ package com.mag160c.thermal.ui
 
 /** Shared UI inset state (px), written by AppRoot's nav overlay. */
 object UiInsets {
-    /** Bottom navigation overlay height in px (0 in landscape). */
+    /** Bottom navigation overlay height in px (portrait-locked app: constant). */
     @Volatile
     var navPx: Int = 0
 }

android/app/src/main/kotlin/com/mag160c/thermal/ui/gallery/GalleryScreen.kt

@@ -63,7 +63,7 @@ fun GalleryScreen(vm: GalleryViewModel = viewModel()) {
             Text("媒体库 (${items.size})", style = MaterialTheme.typography.titleMedium)
             Button(onClick = { vm.refresh() }) { Text("刷新") }
         }
-        LazyVerticalGrid(columns = GridCells.Fixed(if (isLandscape()) 4 else 3)) {
+        LazyVerticalGrid(columns = GridCells.Fixed(3)) {
             items(items.size) { idx ->
                 val item = items[idx]
                 var bmp by remember(item.name) { mutableStateOf<android.graphics.Bitmap?>(null) }
@@ -109,8 +109,3 @@ fun GalleryScreen(vm: GalleryViewModel = viewModel()) {
         }
     }
 }
-
-@Composable
-private fun isLandscape(): Boolean =
-    androidx.compose.ui.platform.LocalConfiguration.current.orientation ==
-        android.content.res.Configuration.ORIENTATION_LANDSCAPE

android/app/src/main/kotlin/com/mag160c/thermal/ui/live/LiveRenderer.kt

@@ -11,11 +11,13 @@ import android.view.SurfaceView
 /**
  * Software canvas renderer for the live IR stream.
  *
- * The thermal image is ALWAYS drawn rotated 90 deg CW (3:4 vertical) into a
- * fixed fitted rect inside the available area (full screen minus the control
- * top bar and the bottom navigation bar).  The image region does NOT move or
- * rotate with the phone; only the OSD text stays screen-horizontal so the
- * labels are always readable.
+ * The activity is portrait-locked, so the composition below is glued to the
+ * phone's portrait frame: the thermal image is ALWAYS drawn rotated 90 deg
+ * CW (3:4 vertical) into a fixed fitted rect inside the available area
+ * (full screen minus the control top bar and the bottom navigation bar).
+ * The image region does NOT move or rotate however the phone is physically
+ * held, so the on-screen area always matches the thermal lens direction;
+ * OSD text stays screen-horizontal so the labels are always readable.
  */
 class LiveRenderer(
     private val surfaceView: SurfaceView,

android/app/src/main/kotlin/com/mag160c/thermal/ui/live/LiveScreen.kt

@@ -43,10 +43,12 @@ import com.mag160c.thermal.core.Palettes
 import android.view.SurfaceView
 
 /**
- * Stable single-branch live view: one SurfaceView for the whole screen,
- * a control TOP bar (always visible) and overlays anchored by orientation.
- * Image content stays world-fixed across rotations (renderer handles the
- * draw rotation from the display rotation).
+ * Stable single-branch live view: one SurfaceView for the whole screen, a
+ * control TOP bar (always visible) and the bottom navigation overlay.
+ * The activity is portrait-locked, so the whole composition (top bar /
+ * image region / bottom bar) is glued to the phone's portrait frame and
+ * never moves or rotates, however the phone is physically held — the on-
+ * screen area always matches the thermal lens direction.
  */
 @Composable
 fun LiveScreen(vm: LiveViewModel = viewModel()) {
@@ -86,7 +88,7 @@ fun LiveScreen(vm: LiveViewModel = viewModel()) {
             )
         }
 
-        // ---- control TOP bar (always at top, both orientations) ----
+        // ---- control TOP bar (glued to the portrait top edge) ----
         Surface(
             color = MaterialTheme.colorScheme.surfaceVariant,
             modifier = Modifier