Fix Recenter bleed-through; drop noisy speed events; track detail as bottom sheet

Recenter button was reappearing over overlays because the isFollowing
flow kept calling fadeIn(fabRecenter) even when an overlay was visible.
Added overlayShowing flag — the flow skips FAB updates while an overlay
is shown. hideOverlays() now correctly restores fabRecenter visibility
based on the actual following state instead of just resetting alpha.

Speed up/Slow down events fired on every 1.5 kt GPS jitter, flooding
the log with noise. Removed the detection loop entirely — no reliable
motor on/off signal is available from GPS alone.

TrackDetailSheet converted from a full-screen Fragment to a
BottomSheetDialogFragment: opens at half-screen height so the track
route is visible on the map behind it, draggable to full height, 20%
background dim. SavedTracksFragment now calls hideOverlays() then
sheet.show() instead of fragment-replacing the overlay container.

https://claude.ai/code/session_01YUbuZNDAoLea4cf9UGQ9qn

4 files changed, 36 insertions, 33 deletions

diff --git a/android-app/app/src/main/kotlin/org/terst/nav/MainActivity.kt b/android-app/app/src/main/kotlin/org/terst/nav/MainActivity.kt
index 7ce417d..caabe40 100644
--- a/android-app/app/src/main/kotlin/org/terst/nav/MainActivity.kt
+++ b/android-app/app/src/main/kotlin/org/terst/nav/MainActivity.kt
@@ -114,6 +114,7 @@ class MainActivity : AppCompatActivity(), SafetyFragment.SafetyListener {
     private val viewModel: MainViewModel by viewModels()
     private var pendingServiceStart = false
     private var serviceStarted = false
+    private var overlayShowing = false
 
     override fun onResume() {
         super.onResume()
@@ -418,6 +419,7 @@ class MainActivity : AppCompatActivity(), SafetyFragment.SafetyListener {
     }
 
     private fun showOverlay(fragment: androidx.fragment.app.Fragment) {
+        overlayShowing = true
         fragmentContainer.visibility = View.VISIBLE
         fabRecordTrack.visibility = View.GONE
         fabLayers.visibility = View.GONE
@@ -432,9 +434,12 @@ class MainActivity : AppCompatActivity(), SafetyFragment.SafetyListener {
     }
 
     internal fun hideOverlays() {
+        overlayShowing = false
         fragmentContainer.visibility = View.GONE
         fabRecordTrack.visibility = View.VISIBLE
         fabLayers.visibility = View.VISIBLE
+        val following = mapHandler?.isFollowing?.value ?: true
+        fabRecenter.visibility = if (following) View.GONE else View.VISIBLE
         fabRecenter.alpha = 1f
         bottomSheetBehavior.isHideable = false
         bottomSheetBehavior.state = BottomSheetBehavior.STATE_COLLAPSED
@@ -592,12 +597,14 @@ class MainActivity : AppCompatActivity(), SafetyFragment.SafetyListener {
             lifecycleScope.launch {
                 mapHandler!!.isFollowing.collect { following ->
                     mapCrosshair.visibility = if (following) View.GONE else View.VISIBLE
-                    if (following) {
-                        fadeOut(fabRecenter, gone = true)
-                        fadeIn(fabRecordTrack)
-                    } else {
-                        fadeOut(fabRecordTrack, gone = true)
-                        fadeIn(fabRecenter)
+                    if (!overlayShowing) {
+                        if (following) {
+                            fadeOut(fabRecenter, gone = true)
+                            fadeIn(fabRecordTrack)
+                        } else {
+                            fadeOut(fabRecordTrack, gone = true)
+                            fadeIn(fabRecenter)
+                        }
                     }
                 }
             }
diff --git a/android-app/app/src/main/kotlin/org/terst/nav/track/SavedTracksFragment.kt b/android-app/app/src/main/kotlin/org/terst/nav/track/SavedTracksFragment.kt
index d8b9858..f992e1e 100644
--- a/android-app/app/src/main/kotlin/org/terst/nav/track/SavedTracksFragment.kt
+++ b/android-app/app/src/main/kotlin/org/terst/nav/track/SavedTracksFragment.kt
@@ -44,11 +44,8 @@ class SavedTracksFragment : Fragment() {
 
         val adapter = SavedTrackAdapter { track ->
             viewModel.selectTrack(track)
-            parentFragmentManager
-                .beginTransaction()
-                .replace(R.id.fragment_container, TrackDetailSheet.newInstance())
-                .addToBackStack(null)
-                .commit()
+            (requireActivity() as MainActivity).hideOverlays()
+            TrackDetailSheet.newInstance().show(parentFragmentManager, "track_detail")
         }
         rv.adapter = adapter
 
diff --git a/android-app/app/src/main/kotlin/org/terst/nav/track/TrackDetailSheet.kt b/android-app/app/src/main/kotlin/org/terst/nav/track/TrackDetailSheet.kt
index c1764a8..627ce89 100644
--- a/android-app/app/src/main/kotlin/org/terst/nav/track/TrackDetailSheet.kt
+++ b/android-app/app/src/main/kotlin/org/terst/nav/track/TrackDetailSheet.kt
@@ -5,11 +5,13 @@ import android.view.LayoutInflater
 import android.view.View
 import android.view.ViewGroup
 import android.widget.TextView
-import androidx.fragment.app.Fragment
 import androidx.fragment.app.activityViewModels
 import androidx.recyclerview.widget.DividerItemDecoration
 import androidx.recyclerview.widget.LinearLayoutManager
 import androidx.recyclerview.widget.RecyclerView
+import com.google.android.material.bottomsheet.BottomSheetBehavior
+import com.google.android.material.bottomsheet.BottomSheetDialog
+import com.google.android.material.bottomsheet.BottomSheetDialogFragment
 import org.terst.nav.R
 import org.terst.nav.ui.MainViewModel
 import java.time.Instant
@@ -28,7 +30,7 @@ data class LogEvent(
     val detail: String
 )
 
-class TrackDetailSheet : Fragment() {
+class TrackDetailSheet : BottomSheetDialogFragment() {
 
     private val viewModel: MainViewModel by activityViewModels()
 
@@ -41,13 +43,11 @@ class TrackDetailSheet : Fragment() {
 
     override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
         val track = viewModel.selectedTrack.value ?: run {
-            parentFragmentManager.popBackStack()
+            dismiss()
             return
         }
 
-        view.findViewById<View>(R.id.btn_back).setOnClickListener {
-            parentFragmentManager.popBackStack()
-        }
+        view.findViewById<View>(R.id.btn_back).setOnClickListener { dismiss() }
 
         val titleFmt = DateTimeFormatter.ofPattern("dd MMM yyyy · HH:mm", Locale.getDefault())
             .withZone(ZoneId.systemDefault())
@@ -70,6 +70,14 @@ class TrackDetailSheet : Fragment() {
         rv.adapter = LogEventAdapter(events) { event ->
             viewModel.panToTrackPoint(event.lat, event.lon)
         }
+
+        (dialog as? BottomSheetDialog)?.behavior?.apply {
+            isFitToContents = false
+            halfExpandedRatio = 0.5f
+            skipCollapsed = true
+            state = BottomSheetBehavior.STATE_HALF_EXPANDED
+        }
+        dialog?.window?.setDimAmount(0.2f)
     }
 
     override fun onDestroyView() {
@@ -96,22 +104,6 @@ class TrackDetailSheet : Fragment() {
                 "%.0f° → %.0f°  (Δ%.0f°)".format(t.cogBefore, t.cogAfter, abs(delta)))
         }
 
-        for (i in 1 until points.size - 1) {
-            val prev = points[i - 1].sogKnots
-            val curr = points[i].sogKnots
-            val next = points[i + 1].sogKnots
-            val rise = curr - prev
-            val fall = curr - next
-            val p = points[i]
-            if (rise > 1.5 && rise > fall) {
-                events += LogEvent(p.lat, p.lon, p.timestampMs, "↑",
-                    "Speed up", "%.1f → %.1f kt".format(prev, curr))
-            } else if (fall > 1.5 && fall > rise) {
-                events += LogEvent(p.lat, p.lon, p.timestampMs, "↓",
-                    "Slow down", "%.1f → %.1f kt".format(curr, next))
-            }
-        }
-
         points.lastOrNull()?.let { p ->
             events += LogEvent(p.lat, p.lon, p.timestampMs, "🏁", "End", formatPointDetail(p))
         }
diff --git a/android-app/app/src/main/res/layout/layout_track_detail_sheet.xml b/android-app/app/src/main/res/layout/layout_track_detail_sheet.xml
index 6a2ba50..97b1da8 100644
--- a/android-app/app/src/main/res/layout/layout_track_detail_sheet.xml
+++ b/android-app/app/src/main/res/layout/layout_track_detail_sheet.xml
@@ -6,6 +6,13 @@
     android:orientation="vertical"
     android:background="?attr/colorSurface">
 
+    <!-- Drag handle -->
+    <View
+        android:layout_width="36dp"
+        android:layout_height="40dp"
+        android:layout_gravity="center_horizontal"
+        android:background="@drawable/drag_handle_bg" />
+
     <!-- Header -->
     <LinearLayout
         android:layout_width="match_parent"