Auto commit Thu Mar 19 05:01:02 PM CDT 2026

app/src/main/java/com/mindmachine/mvp/session/TimelineEditorScreen.kt

@@ -21,12 +21,10 @@ import androidx.compose.foundation.shape.RoundedCornerShape
 import androidx.compose.material3.Button
 import androidx.compose.material3.MaterialTheme
 import androidx.compose.material3.OutlinedButton
-import androidx.compose.material3.Slider
 import androidx.compose.material3.Text
 import androidx.compose.runtime.Composable
 import androidx.compose.runtime.LaunchedEffect
 import androidx.compose.runtime.getValue
-import androidx.compose.runtime.mutableFloatStateOf
 import androidx.compose.runtime.mutableIntStateOf
 import androidx.compose.runtime.mutableStateOf
 import androidx.compose.runtime.remember
@@ -34,7 +32,6 @@ import androidx.compose.runtime.setValue
 import androidx.compose.ui.Alignment
 import androidx.compose.ui.Modifier
 import androidx.compose.ui.geometry.Offset
-import androidx.compose.ui.geometry.Rect
 import androidx.compose.ui.graphics.Color
 import androidx.compose.ui.graphics.Path
 import androidx.compose.ui.input.pointer.pointerInput
@@ -48,7 +45,6 @@ import com.mindmachine.mvp.session.TimelineEditorState.ActiveCurve
 import kotlin.math.abs
 import kotlin.math.max
 import kotlin.math.min
-import kotlin.math.roundToInt
 
 @Composable
 fun TimelineEditorScreen(
@@ -73,7 +69,9 @@ fun TimelineEditorScreen(
 
     var revealSignal by remember { mutableIntStateOf(0) }
     TimelineEditorRoot(
-        modifier = Modifier.fillMaxSize().background(MaterialTheme.colorScheme.background),
+        modifier = Modifier
+            .fillMaxSize()
+            .background(MaterialTheme.colorScheme.background),
         onRevealSystemBars = { revealSignal += 1 },
         revealSignal = revealSignal,
     ) {
@@ -117,16 +115,64 @@ private fun TimelineEditorContent(
 ) {
     var state by remember { mutableStateOf(TimelineEditorState.default()) }
 
-    Column(Modifier.fillMaxSize().padding(12.dp), verticalArrangement = Arrangement.spacedBy(10.dp)) {
-        Row(Modifier.fillMaxWidth(), horizontalArrangement = Arrangement.SpaceBetween, verticalAlignment = Alignment.CenterVertically) {
-            Text("Timeline Editor", style = MaterialTheme.typography.titleLarge, color = MaterialTheme.colorScheme.onBackground)
+    // Simple preview playhead (UI-only for now).
+    LaunchedEffect(state.isPlaying, state.durationSec) {
+        if (!state.isPlaying) return@LaunchedEffect
+        val start = state.playheadSec
+        val t0 = System.currentTimeMillis()
+        while (state.isPlaying) {
+            val elapsed = (System.currentTimeMillis() - t0) / 1000f
+            val next = (start + elapsed)
+            val wrapped = if (next > state.durationSec) 0f else next
+            state = state.copy(playheadSec = wrapped)
+            kotlinx.coroutines.delay(16)
+        }
+    }
+
+    Column(
+        Modifier
+            .fillMaxSize()
+            .padding(12.dp),
+        verticalArrangement = Arrangement.spacedBy(10.dp)
+    ) {
+        Row(
+            Modifier.fillMaxWidth(),
+            horizontalArrangement = Arrangement.SpaceBetween,
+            verticalAlignment = Alignment.CenterVertically
+        ) {
+            Text(
+                "Timeline Editor",
+                style = MaterialTheme.typography.titleLarge,
+                color = MaterialTheme.colorScheme.onBackground
+            )
             OutlinedButton(onClick = onBack) { Text("Back") }
         }
 
-        DurationSlider(
-            durationSec = state.durationSec,
-            onDurationChanged = { state = state.copy(durationSec = it) },
-        )
+        Row(
+            Modifier
+                .fillMaxWidth()
+                .background(MaterialTheme.colorScheme.surface, RoundedCornerShape(12.dp))
+                .padding(12.dp),
+            horizontalArrangement = Arrangement.SpaceBetween,
+            verticalAlignment = Alignment.CenterVertically
+        ) {
+            Column {
+                Text("Selected duration", color = MaterialTheme.colorScheme.onSurface)
+                Text(
+                    formatDuration(state.selection.durationSec.coerceAtLeast(0)),
+                    style = MaterialTheme.typography.titleMedium,
+                    color = MaterialTheme.colorScheme.onSurface
+                )
+            }
+            Row(horizontalArrangement = Arrangement.spacedBy(10.dp)) {
+                OutlinedButton(onClick = { state = state.copy(isPlaying = !state.isPlaying) }) {
+                    Text(if (state.isPlaying) "Pause" else "Play")
+                }
+                OutlinedButton(onClick = { state = state.copy(playheadSec = 0f) }) {
+                    Text("Rewind")
+                }
+            }
+        }
 
         CurveSelector(
             active = state.activeCurve,
@@ -141,14 +187,14 @@ private fun TimelineEditorContent(
             curveRight = state.visualRight,
             activeCurve = state.activeCurve,
             viewport = state.viewport,
+            selection = state.selection,
+            playheadSec = state.playheadSec,
             onViewportChanged = { state = state.copy(viewport = it) },
+            onSelectionChanged = { sel -> state = state.copy(selection = sel).clampSelection() },
             onUpdateCurve = { curveId, newCurve ->
-                state = when (curveId) {
-                    ActiveCurve.VISUAL_LEFT -> state.copy(visualLeft = newCurve)
-                    ActiveCurve.VISUAL_RIGHT -> state.copy(visualRight = newCurve)
-                    ActiveCurve.AUDIO_LEFT -> state // ignored
-                    ActiveCurve.AUDIO_RIGHT -> state // ignored
-                }
+                val candidate = state.withCurve(curveId, newCurve)
+                val maxT = newCurve.points.maxOfOrNull { it.tSec } ?: 0
+                state = candidate.extendDurationTo(maxT).copy(selection = candidate.selection.copy(endSec = max(candidate.selection.endSec, state.durationSec)))
             },
             onTapSideSelect = { side ->
                 state = state.copy(activeCurve = if (side == Side.LEFT) ActiveCurve.VISUAL_LEFT else ActiveCurve.VISUAL_RIGHT)
@@ -157,20 +203,20 @@ private fun TimelineEditorContent(
 
         TimelineGraph(
             title = "Audio",
-            leftLabel = "Carrier",
-            rightLabel = "Binaural",
+            leftLabel = "Carrier Frequency",
+            rightLabel = "Binaural Beat",
             curveLeft = state.audioLeft,
             curveRight = state.audioRight,
             activeCurve = state.activeCurve,
             viewport = state.viewport,
+            selection = state.selection,
+            playheadSec = state.playheadSec,
             onViewportChanged = { state = state.copy(viewport = it) },
+            onSelectionChanged = { sel -> state = state.copy(selection = sel).clampSelection() },
             onUpdateCurve = { curveId, newCurve ->
-                state = when (curveId) {
-                    ActiveCurve.AUDIO_LEFT -> state.copy(audioLeft = newCurve)
-                    ActiveCurve.AUDIO_RIGHT -> state.copy(audioRight = newCurve)
-                    ActiveCurve.VISUAL_LEFT -> state // ignored
-                    ActiveCurve.VISUAL_RIGHT -> state // ignored
-                }
+                val candidate = state.withCurve(curveId, newCurve)
+                val maxT = newCurve.points.maxOfOrNull { it.tSec } ?: 0
+                state = candidate.extendDurationTo(maxT)
             },
             onTapSideSelect = { side ->
                 state = state.copy(activeCurve = if (side == Side.LEFT) ActiveCurve.AUDIO_LEFT else ActiveCurve.AUDIO_RIGHT)
@@ -179,38 +225,22 @@ private fun TimelineEditorContent(
 
         Spacer(Modifier.height(4.dp))
         Row(Modifier.fillMaxWidth(), horizontalArrangement = Arrangement.spacedBy(10.dp)) {
-            Button(onClick = { state = TimelineEditorState.default(durationSec = state.durationSec) }, modifier = Modifier.weight(1f)) {
+            Button(
+                onClick = { state = TimelineEditorState.default(durationSec = state.durationSec) },
+                modifier = Modifier.weight(1f)
+            ) {
                 Text("Reset")
             }
-            OutlinedButton(onClick = { /* TODO persist into session config */ }, modifier = Modifier.weight(1f)) {
+            OutlinedButton(
+                onClick = { /* TODO persist into session config */ },
+                modifier = Modifier.weight(1f)
+            ) {
                 Text("Save")
             }
         }
     }
 }
 
-@Composable
-private fun DurationSlider(
-    durationSec: Int,
-    onDurationChanged: (Int) -> Unit,
-) {
-    val minSec = 60
-    val maxSec = 8 * 60 * 60
-    val clamped = durationSec.coerceIn(minSec, maxSec)
-    val value = clamped.toFloat()
-
-    Column(Modifier.fillMaxWidth().background(MaterialTheme.colorScheme.surface, RoundedCornerShape(12.dp)).padding(12.dp)) {
-        Text("Duration", color = MaterialTheme.colorScheme.onSurface)
-        Text(formatDuration(clamped), style = MaterialTheme.typography.titleMedium, color = MaterialTheme.colorScheme.onSurface)
-        Slider(
-            value = value,
-            onValueChange = { onDurationChanged(it.roundToInt().coerceIn(minSec, maxSec)) },
-            valueRange = minSec.toFloat()..maxSec.toFloat(),
-        )
-        Text("1 minute  8 hours", color = MaterialTheme.colorScheme.onSurface, style = MaterialTheme.typography.bodySmall)
-    }
-}
-
 private enum class Side { LEFT, RIGHT }
 
 @Composable
@@ -218,7 +248,12 @@ private fun CurveSelector(
     active: ActiveCurve,
     onSelect: (ActiveCurve) -> Unit,
 ) {
-    Column(Modifier.fillMaxWidth().background(MaterialTheme.colorScheme.surface, RoundedCornerShape(12.dp)).padding(12.dp)) {
+    Column(
+        Modifier
+            .fillMaxWidth()
+            .background(MaterialTheme.colorScheme.surface, RoundedCornerShape(12.dp))
+            .padding(12.dp)
+    ) {
         Text("Curve selection", color = MaterialTheme.colorScheme.onSurface)
         Row(Modifier.fillMaxWidth(), horizontalArrangement = Arrangement.SpaceBetween) {
             Column(Modifier.weight(1f)) {
@@ -237,7 +272,7 @@ private fun CurveSelector(
             }
         }
         Text(
-            "Tip: you can also tap left/right side of a graph to select the corresponding curve.",
+            "Tip: tap left/right side of a graph to select that curve. Double-tap between points to add a smoothed point.",
             color = MaterialTheme.colorScheme.onSurface,
             style = MaterialTheme.typography.bodySmall,
         )
@@ -264,6 +299,8 @@ private fun SelectorChip(
     }
 }
 
+private enum class HandleDrag { NONE, START, END }
+
 @Composable
 private fun TimelineGraph(
     title: String,
@@ -273,7 +310,10 @@ private fun TimelineGraph(
     curveRight: TimelineCurve,
     activeCurve: ActiveCurve,
     viewport: TimelineViewport,
+    selection: TimelineSelection,
+    playheadSec: Float,
     onViewportChanged: (TimelineViewport) -> Unit,
+    onSelectionChanged: (TimelineSelection) -> Unit,
     onUpdateCurve: (ActiveCurve, TimelineCurve) -> Unit,
     onTapSideSelect: (Side) -> Unit,
 ) {
@@ -286,7 +326,15 @@ private fun TimelineGraph(
 
     val context = LocalContext.current
 
-    Column(Modifier.fillMaxWidth().height(240.dp).background(MaterialTheme.colorScheme.surface, RoundedCornerShape(12.dp)).padding(10.dp)) {
+    var dragMode by remember { mutableStateOf(HandleDrag.NONE) }
+
+    Column(
+        Modifier
+            .fillMaxWidth()
+            .height(260.dp)
+            .background(MaterialTheme.colorScheme.surface, RoundedCornerShape(12.dp))
+            .padding(10.dp)
+    ) {
         Row(Modifier.fillMaxWidth(), horizontalArrangement = Arrangement.SpaceBetween, verticalAlignment = Alignment.CenterVertically) {
             Text(title, color = MaterialTheme.colorScheme.onSurface, style = MaterialTheme.typography.titleMedium)
             Text(
@@ -308,22 +356,43 @@ private fun TimelineGraph(
         Box(
             modifier = Modifier
                 .fillMaxWidth()
-                .height(180.dp)
+                .height(190.dp)
                 .background(Color(0xFF0A0E18), RoundedCornerShape(10.dp))
-                .pointerInput(Unit) {
+                .pointerInput(viewport, selection) {
                     detectDragGestures(
+                        onDragStart = { start ->
+                            val w = size.width.toFloat()
+                            val startX = viewport.timeToX(selection.startSec, w)
+                            val endX = viewport.timeToX(selection.endSec, w)
+                            val hitPx = 32f
+                            dragMode = when {
+                                abs(start.x - startX) <= hitPx -> HandleDrag.START
+                                abs(start.x - endX) <= hitPx -> HandleDrag.END
+                                else -> HandleDrag.NONE
+                            }
+                        },
+                        onDragEnd = { dragMode = HandleDrag.NONE },
+                        onDragCancel = { dragMode = HandleDrag.NONE },
                         onDrag = { change, dragAmount ->
-                            // If user drags without grabbing a point, treat as pan.
-                            val didHitLeft = curveLeft.hitTestPoint(change.position, viewport, size.width.toFloat(), size.height.toFloat()) != null
-                            val didHitRight = curveRight.hitTestPoint(change.position, viewport, size.width.toFloat(), size.height.toFloat()) != null
-                            if (!didHitLeft && !didHitRight) {
-                                val newViewport = viewport.applyZoomPan(
-                                    zoomChange = 1f,
-                                    panPx = dragAmount.x,
-                                    widthPx = size.width.toFloat(),
-                                    centroidPx = size.width.toFloat() / 2f,
-                                )
-                                onViewportChanged(newViewport)
+                            val w = size.width.toFloat()
+                            val t = viewport.xToTimeSec(change.position.x + dragAmount.x, w).toInt().coerceAtLeast(0)
+                            when (dragMode) {
+                                HandleDrag.START -> onSelectionChanged(TimelineSelection(startSec = min(t, selection.endSec - 60), endSec = selection.endSec))
+                                HandleDrag.END -> onSelectionChanged(TimelineSelection(startSec = selection.startSec, endSec = max(t, selection.startSec + 60)))
+                                HandleDrag.NONE -> {
+                                    // background pan (when not dragging a point)
+                                    val didHitLeft = curveLeft.hitTestPoint(change.position, viewport, w, size.height.toFloat()) != null
+                                    val didHitRight = curveRight.hitTestPoint(change.position, viewport, w, size.height.toFloat()) != null
+                                    if (!didHitLeft && !didHitRight) {
+                                        val newViewport = viewport.applyZoomPan(
+                                            zoomChange = 1f,
+                                            panPx = dragAmount.x,
+                                            widthPx = w,
+                                            centroidPx = w / 2f,
+                                        )
+                                        onViewportChanged(newViewport)
+                                    }
+                                }
                             }
                         }
                     )
@@ -345,9 +414,21 @@ private fun TimelineGraph(
                             val side = if (offset.x < size.width / 2f) Side.LEFT else Side.RIGHT
                             onTapSideSelect(side)
                         },
-                        onDoubleTap = { /* TODO smooth */ },
+                        onDoubleTap = { offset ->
+                            val curveId = when (activeCurve) {
+                                leftId, rightId -> activeCurve
+                                else -> leftId
+                            }
+                            val targetCurve = if (curveId == leftId) curveLeft else curveRight
+                            val updated = targetCurve.insertSmoothedPointAt(offset, viewport, size.width.toFloat(), size.height.toFloat())
+                            onCurveEditedHaptic()
+                            onUpdateCurve(curveId, updated)
+                        },
                         onLongPress = { offset ->
-                            val curveId = if (activeCurve == leftId || activeCurve == rightId) activeCurve else leftId
+                            val curveId = when (activeCurve) {
+                                leftId, rightId -> activeCurve
+                                else -> leftId
+                            }
                             val targetCurve = if (curveId == leftId) curveLeft else curveRight
                             val hit = targetCurve.hitTestPoint(offset, viewport, size.width.toFloat(), size.height.toFloat())
                             if (hit != null) {
@@ -378,7 +459,6 @@ private fun TimelineGraph(
                 }
                 .pointerInput(activeCurve, viewport, curveLeft, curveRight) {
                     detectDragGestures(
-                        onDragStart = { /* no-op */ },
                         onDrag = { change, dragAmount ->
                             val curveId = when (activeCurve) {
                                 leftId, rightId -> activeCurve
@@ -402,17 +482,39 @@ private fun TimelineGraph(
         ) {
             Canvas(modifier = Modifier.fillMaxSize()) {
                 drawGrid()
+
+                // selection range overlay + handles
+                val startX = viewport.timeToX(selection.startSec, size.width)
+                val endX = viewport.timeToX(selection.endSec, size.width)
+                drawRect(
+                    color = Color.White.copy(alpha = 0.06f),
+                    topLeft = Offset(min(startX, endX), 0f),
+                    size = androidx.compose.ui.geometry.Size(abs(endX - startX), size.height)
+                )
+                drawLine(Color.White.copy(alpha = 0.35f), Offset(startX, 0f), Offset(startX, size.height), strokeWidth = 3f)
+                drawLine(Color.White.copy(alpha = 0.35f), Offset(endX, 0f), Offset(endX, size.height), strokeWidth = 3f)
+
+                val handleColor = Color.White.copy(alpha = 0.9f)
+                drawCircle(handleColor, radius = 10f, center = Offset(startX, size.height - 14f))
+                drawCircle(handleColor, radius = 10f, center = Offset(endX, size.height - 14f))
+
+                // playhead
+                val playX = viewport.timeToX(playheadSec.toInt(), size.width)
+                drawLine(Color(0xFFFFD54F).copy(alpha = 0.9f), Offset(playX, 0f), Offset(playX, size.height), strokeWidth = 2f)
+
                 drawCurve(curveLeft, selected = selectedLeft, color = if (isVisual) Color(0xFF4D8BFF) else Color(0xFF55E39A), viewport = viewport)
                 drawCurve(curveRight, selected = selectedRight, color = if (isVisual) Color(0xFF7AB8FF) else Color(0xFF2FCB7C), viewport = viewport)
             }
         }
 
         Text(
-            "Tap to add • Drag to move • Long-press to delete • Pinch to zoom • Drag background to pan (WIP)",
+            "Tap add • Drag point move • Long-press delete • Double-tap smooth • Pinch zoom • Drag background pan • Drag handles to set range",
             color = MaterialTheme.colorScheme.onSurface.copy(alpha = 0.75f),
             style = MaterialTheme.typography.bodySmall,
             textAlign = TextAlign.Center,
-            modifier = Modifier.fillMaxWidth().padding(top = 6.dp)
+            modifier = Modifier
+                .fillMaxWidth()
+                .padding(top = 6.dp)
         )
     }
 }
@@ -444,7 +546,11 @@ private fun androidx.compose.ui.graphics.drawscope.DrawScope.drawCurve(
         if (idx == 0) path.moveTo(x, y) else path.lineTo(x, y)
     }
     val stroke = if (selected) 6f else 3f
-    drawPath(path, color = if (selected) color.copy(alpha = 1f) else color.copy(alpha = 0.55f), style = androidx.compose.ui.graphics.drawscope.Stroke(width = stroke))
+    drawPath(
+        path,
+        color = if (selected) color.copy(alpha = 1f) else color.copy(alpha = 0.55f),
+        style = androidx.compose.ui.graphics.drawscope.Stroke(width = stroke)
+    )
 
     pts.forEach { p ->
         val x = viewport.timeToX(p.tSec, size.width)

app/src/main/java/com/mindmachine/mvp/session/TimelineEditorState.kt

@@ -1,16 +1,20 @@
 package com.mindmachine.mvp.session
 
+import kotlin.math.abs
 import kotlin.math.max
 import kotlin.math.min
 
 data class TimelineEditorState(
     val durationSec: Int,
+    val selection: TimelineSelection,
     val viewport: TimelineViewport,
     val activeCurve: ActiveCurve,
     val visualLeft: TimelineCurve,
     val visualRight: TimelineCurve,
     val audioLeft: TimelineCurve,
     val audioRight: TimelineCurve,
+    val isPlaying: Boolean,
+    val playheadSec: Float,
 ) {
     enum class ActiveCurve {
         VISUAL_LEFT,
@@ -21,26 +25,92 @@ data class TimelineEditorState(
 
     companion object {
         fun default(durationSec: Int = 20 * 60): TimelineEditorState {
+            val dur = durationSec.coerceIn(60, 8 * 60 * 60)
             val initial = TimelineCurve(
                 points = listOf(
                     TimelinePoint(0, 0.5f),
-                    TimelinePoint(durationSec, 0.5f),
+                    TimelinePoint(dur, 0.5f),
                 )
             )
             return TimelineEditorState(
-                durationSec = durationSec,
+                durationSec = dur,
+                selection = TimelineSelection(0, dur),
                 viewport = TimelineViewport(
                     startSec = 0f,
-                    secondsPerScreen = min(10f * 60f, durationSec.toFloat())
+                    secondsPerScreen = min(10f * 60f, dur.toFloat())
                 ),
                 activeCurve = ActiveCurve.VISUAL_LEFT,
                 visualLeft = initial,
                 visualRight = initial,
                 audioLeft = initial,
                 audioRight = initial,
+                isPlaying = false,
+                playheadSec = 0f,
             )
         }
     }
+
+    fun curveFor(id: ActiveCurve): TimelineCurve = when (id) {
+        ActiveCurve.VISUAL_LEFT -> visualLeft
+        ActiveCurve.VISUAL_RIGHT -> visualRight
+        ActiveCurve.AUDIO_LEFT -> audioLeft
+        ActiveCurve.AUDIO_RIGHT -> audioRight
+    }
+
+    fun withCurve(id: ActiveCurve, curve: TimelineCurve): TimelineEditorState = when (id) {
+        ActiveCurve.VISUAL_LEFT -> copy(visualLeft = curve)
+        ActiveCurve.VISUAL_RIGHT -> copy(visualRight = curve)
+        ActiveCurve.AUDIO_LEFT -> copy(audioLeft = curve)
+        ActiveCurve.AUDIO_RIGHT -> copy(audioRight = curve)
+    }
+
+    /**
+     * Spec: auto-extend timeline when user creates/moves points beyond current duration.
+     * Also preserve the last value to the new end of the session.
+     */
+    fun extendDurationTo(atLeastSec: Int): TimelineEditorState {
+        val newDur = atLeastSec.coerceIn(60, 8 * 60 * 60)
+        if (newDur <= durationSec) return this
+
+        fun extendCurve(c: TimelineCurve): TimelineCurve = c.extendTo(newDur)
+
+        val updated = copy(
+            durationSec = newDur,
+            selection = selection.copy(endSec = max(selection.endSec, newDur)),
+            visualLeft = extendCurve(visualLeft),
+            visualRight = extendCurve(visualRight),
+            audioLeft = extendCurve(audioLeft),
+            audioRight = extendCurve(audioRight),
+        )
+
+        // Keep viewport zoom but ensure end is reachable by panning.
+        return updated
+    }
+
+    fun clampSelection(): TimelineEditorState {
+        val minDur = 60
+        val maxDur = 8 * 60 * 60
+        val start = selection.startSec.coerceIn(0, durationSec)
+        var end = selection.endSec.coerceIn(0, durationSec)
+        if (end - start < minDur) end = (start + minDur).coerceAtMost(durationSec)
+        val clamped = TimelineSelection(start, end)
+        val newDuration = (clamped.endSec - clamped.startSec).coerceIn(minDur, maxDur)
+        // For now we keep selection anchored at 0; if start moved, reflect it but don't shift curves.
+        return copy(durationSec = max(durationSec, clamped.endSec), selection = clamped).let {
+            it.copy(durationSec = it.durationSec.coerceIn(minDur, maxDur))
+        }
+    }
+}
+
+data class TimelineSelection(
+    val startSec: Int,
+    val endSec: Int,
+) {
+    init {
+        require(endSec >= startSec) { "endSec must be >= startSec" }
+    }
+
+    val durationSec: Int get() = endSec - startSec
 }
 
 data class TimelineViewport(
@@ -53,6 +123,7 @@ data class TimelineViewport(
         widthPx: Float,
         centroidPx: Float,
     ): TimelineViewport {
+        // Spec: Minimum zoom = 30 seconds per screen width; maximum zoom = 24 hours visible.
         val minSecondsPerScreen = 30f
         val maxSecondsPerScreen = 24f * 60f * 60f
 
@@ -76,13 +147,17 @@ data class TimelineViewport(
         val rel = tSec.toFloat() - startSec
         return (rel / secondsPerScreen) * widthPx
     }
+
+    fun xToTimeSec(xPx: Float, widthPx: Float): Float {
+        return startSec + (xPx / widthPx) * secondsPerScreen
+    }
 }
 
 data class TimelineCurve(
     val points: List<TimelinePoint>
 ) {
     fun addPointAt(offset: androidx.compose.ui.geometry.Offset, viewport: TimelineViewport, widthPx: Float, heightPx: Float): TimelineCurve {
-        val t = (viewport.startSec + (offset.x / widthPx) * viewport.secondsPerScreen).toInt().coerceAtLeast(0)
+        val t = viewport.xToTimeSec(offset.x, widthPx).toInt().coerceAtLeast(0)
         val v = (1f - (offset.y / heightPx)).coerceIn(0f, 1f)
         return copy(points = (points + TimelinePoint(t, v)).sortedBy { it.tSec })
     }
@@ -93,7 +168,7 @@ data class TimelineCurve(
     }
 
     fun movePoint(index: Int, newPosition: androidx.compose.ui.geometry.Offset, viewport: TimelineViewport, widthPx: Float, heightPx: Float): TimelineCurve {
-        val t = (viewport.startSec + (newPosition.x / widthPx) * viewport.secondsPerScreen).toInt().coerceAtLeast(0)
+        val t = viewport.xToTimeSec(newPosition.x, widthPx).toInt().coerceAtLeast(0)
         val v = (1f - (newPosition.y / heightPx)).coerceIn(0f, 1f)
         val updated = points.toMutableList()
         updated[index] = updated[index].copy(tSec = t, value01 = v)
@@ -111,6 +186,36 @@ data class TimelineCurve(
         }
         return null
     }
+
+    fun extendTo(newDurationSec: Int): TimelineCurve {
+        if (points.isEmpty()) return this
+        val sorted = points.sortedBy { it.tSec }
+        val last = sorted.last()
+        if (last.tSec >= newDurationSec) return this
+        return copy(points = (sorted + last.copy(tSec = newDurationSec)).sortedBy { it.tSec })
+    }
+
+    /**
+     * Double-tap gesture: "smooth" by inserting an interpolated point in the nearest segment.
+     */
+    fun insertSmoothedPointAt(offset: androidx.compose.ui.geometry.Offset, viewport: TimelineViewport, widthPx: Float, heightPx: Float): TimelineCurve {
+        val t = viewport.xToTimeSec(offset.x, widthPx).toInt().coerceAtLeast(0)
+        val sorted = points.sortedBy { it.tSec }
+        if (sorted.size < 2) return this
+
+        val rightIndex = sorted.indexOfFirst { it.tSec >= t }.let { if (it == -1) sorted.lastIndex else it }
+        val leftIndex = (rightIndex - 1).coerceAtLeast(0)
+        if (leftIndex == rightIndex) return this
+
+        val a = sorted[leftIndex]
+        val b = sorted[rightIndex]
+        val tt = if (b.tSec == a.tSec) 0f else (t - a.tSec).toFloat() / (b.tSec - a.tSec).toFloat()
+        val v = a.value01 + (b.value01 - a.value01) * tt
+
+        // Only insert if not extremely close to an existing point.
+        if (abs(a.tSec - t) < 1 || abs(b.tSec - t) < 1) return this
+        return copy(points = (sorted + TimelinePoint(t, v.coerceIn(0f, 1f))).sortedBy { it.tSec })
+    }
 }
 
 data class TimelinePoint(

app/src/main/java/com/mindmachine/mvp/session/TimelineParameters.kt

@@ -0,0 +1,102 @@
+package com.mindmachine.mvp.session
+
+import kotlin.math.ln
+import kotlin.math.pow
+
+/**
+ * Parameter definitions + scaling helpers.
+ *
+ * Internally, the editor stores point values as normalized [0,1].
+ * We map to real parameter values using a logarithmic scale where required.
+ */
+object TimelineParameters {
+
+    enum class ParameterId {
+        BRIGHTNESS,
+        BLINK_RATE,
+        CARRIER_FREQUENCY,
+        BINAURAL_BEAT,
+    }
+
+    data class Range(
+        val min: Float,
+        val max: Float,
+        val logScale: Boolean,
+        val units: String,
+    ) {
+        init {
+            require(min > 0f) { "min must be > 0 for log scaling math" }
+            require(max > min) { "max must be > min" }
+        }
+    }
+
+    val ranges: Map<ParameterId, Range> = mapOf(
+        // Brightness is special-cased to allow true 0 while still using a log-ish curve above 0.
+        ParameterId.BRIGHTNESS to Range(min = 0.0001f, max = 1.0f, logScale = true, units = "%"),
+        ParameterId.BLINK_RATE to Range(min = 0.1f, max = 30f, logScale = true, units = "Hz"),
+        ParameterId.CARRIER_FREQUENCY to Range(min = 200f, max = 1200f, logScale = true, units = "Hz"),
+        ParameterId.BINAURAL_BEAT to Range(min = 0.5f, max = 30f, logScale = true, units = "Hz"),
+    )
+
+    fun parameterForCurve(curve: TimelineEditorState.ActiveCurve): ParameterId {
+        return when (curve) {
+            TimelineEditorState.ActiveCurve.VISUAL_LEFT -> ParameterId.BRIGHTNESS
+            TimelineEditorState.ActiveCurve.VISUAL_RIGHT -> ParameterId.BLINK_RATE
+            TimelineEditorState.ActiveCurve.AUDIO_LEFT -> ParameterId.CARRIER_FREQUENCY
+            TimelineEditorState.ActiveCurve.AUDIO_RIGHT -> ParameterId.BINAURAL_BEAT
+        }
+    }
+
+    /**
+     * normalized [0,1] -> actual value in parameter units.
+     */
+    fun denormalize(curve: TimelineEditorState.ActiveCurve, value01: Float): Float {
+        val p = parameterForCurve(curve)
+        val r = ranges.getValue(p)
+        val t = value01.coerceIn(0f, 1f)
+
+        // Brightness: allow exact 0.
+        if (p == ParameterId.BRIGHTNESS && t <= 0f) return 0f
+
+        return if (r.logScale) logDenormalize(t, r.min, r.max) else lerp(r.min, r.max, t)
+    }
+
+    /**
+     * actual value -> normalized [0,1].
+     */
+    fun normalize(curve: TimelineEditorState.ActiveCurve, value: Float): Float {
+        val p = parameterForCurve(curve)
+        val r = ranges.getValue(p)
+
+        // Brightness: allow exact 0.
+        if (p == ParameterId.BRIGHTNESS && value <= 0f) return 0f
+
+        val clamped = value.coerceIn(r.min, r.max)
+        return if (r.logScale) logNormalize(clamped, r.min, r.max) else invLerp(r.min, r.max, clamped)
+    }
+
+    private fun lerp(a: Float, b: Float, t: Float): Float = a + (b - a) * t
+    private fun invLerp(a: Float, b: Float, v: Float): Float = ((v - a) / (b - a)).coerceIn(0f, 1f)
+
+    private fun logNormalize(v: Float, min: Float, max: Float): Float {
+        // Map multiplicative range to linear [0,1].
+        val lnMin = ln(min)
+        val lnMax = ln(max)
+        return ((ln(v) - lnMin) / (lnMax - lnMin)).toFloat().coerceIn(0f, 1f)
+    }
+
+    private fun logDenormalize(t: Float, min: Float, max: Float): Float {
+        val lnMin = ln(min)
+        val lnMax = ln(max)
+        val lnV = lnMin + (lnMax - lnMin) * t
+        return kotlin.math.exp(lnV).toFloat().coerceIn(min, max)
+    }
+
+    /** Brightness is stored in 0..1 but user-facing is 0..100%. */
+    fun brightnessPercentFromNormalized(value01: Float): Int {
+        val t = value01.coerceIn(0f, 1f)
+        if (t <= 0f) return 0
+        val v = logDenormalize(t, ranges.getValue(ParameterId.BRIGHTNESS).min, 1.0f)
+        return (v * 100f).toInt().coerceIn(0, 100)
+    }
+}