feat(win,android): implement timeline seek control

- Added SEEK command to the UDP protocol\n- Windows: Replaced ProgressBar with Slider, bound to SeekCommand\n- Windows: Handled SMTC seek requests to forward to Android\n- Android: Replaced LinearProgressIndicator with Slider, sending SEEK action to service\n- Android: Handled incoming SEEK requests to control the local media session

Author: jayfunc

Android/app/src/main/java/com/jayfunc/carpecast/MainActivity.kt

@@ -36,6 +36,7 @@ import androidx.compose.foundation.layout.ColumnScope
 import androidx.compose.foundation.layout.Row
 import androidx.compose.foundation.layout.Spacer
 import androidx.compose.foundation.layout.aspectRatio
+import androidx.compose.foundation.layout.fillMaxHeight
 import androidx.compose.foundation.layout.fillMaxSize
 import androidx.compose.foundation.layout.fillMaxWidth
 import androidx.compose.foundation.layout.height
@@ -73,6 +74,7 @@ import androidx.compose.material3.OutlinedButton
 import androidx.compose.material3.OutlinedTextField
 import androidx.compose.material3.RadioButton
 import androidx.compose.material3.Scaffold
+import androidx.compose.material3.Slider
 import androidx.compose.material3.Surface
 import androidx.compose.material3.Text
 import androidx.compose.material3.TextButton
@@ -86,6 +88,7 @@ import androidx.compose.runtime.Composable
 import androidx.compose.runtime.DisposableEffect
 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
@@ -481,15 +484,31 @@ fun PlayerScreen(state: MediaState) {
 
             // Progress
             Column(modifier = Modifier.fillMaxWidth()) {
-                val progress = if (state.duration > 0) state.position.toFloat() / state.duration else 0f
-                LinearProgressIndicator(
-                    progress = progress.coerceIn(0f, 1f),
-                    modifier = Modifier
-                        .fillMaxWidth()
-                        .height(6.dp)
-                        .clip(RoundedCornerShape(50)),
-                    color = MaterialTheme.colorScheme.primary,
-                    trackColor = MaterialTheme.colorScheme.primaryContainer
+                var sliderValue by remember { mutableFloatStateOf(0f) }
+                var isDragging by remember { mutableStateOf(false) }
+
+                LaunchedEffect(state.position, state.duration, isDragging) {
+                    if (!isDragging) {
+                        sliderValue = if (state.duration > 0) state.position.toFloat() / state.duration else 0f
+                    }
+                }
+
+                Slider(
+                    value = sliderValue.coerceIn(0f, 1f),
+                    onValueChange = { 
+                        isDragging = true
+                        sliderValue = it 
+                    },
+                    onValueChangeFinished = {
+                        isDragging = false
+                        val targetPos = (sliderValue * state.duration).toLong()
+                        val intent = Intent(context, MediaSyncService::class.java).apply {
+                            action = "ACTION_SEEK"
+                            putExtra("position", targetPos)
+                        }
+                        context.startService(intent)
+                    },
+                    modifier = Modifier.fillMaxWidth()
                 )
 
                 Row(
@@ -498,8 +517,9 @@ fun PlayerScreen(state: MediaState) {
                         .padding(top = 8.dp),
                     horizontalArrangement = Arrangement.SpaceBetween
                 ) {
+                    val currentDisplayPosition = if (isDragging) (sliderValue * state.duration).toLong() else state.position
                     Text(
-                        formatTime(state.position),
+                        formatTime(currentDisplayPosition),
                         style = MaterialTheme.typography.labelMedium,
                         color = MaterialTheme.colorScheme.onSurfaceVariant
                     )

Android/app/src/main/java/com/jayfunc/carpecast/MediaSyncService.kt

@@ -434,6 +434,12 @@ class MediaSyncService : NotificationListenerService() {
 
                 "ACTION_NEXT" -> controller?.transportControls?.skipToNext()
                 "ACTION_PREV" -> controller?.transportControls?.skipToPrevious()
+                "ACTION_SEEK" -> {
+                    val position = intent.getLongExtra("position", -1L)
+                    if (position != -1L) {
+                        controller?.transportControls?.seekTo(position)
+                    }
+                }
             }
         }
         return START_STICKY
@@ -449,6 +455,16 @@ class MediaSyncService : NotificationListenerService() {
 
             val controller = activeControllers.firstOrNull() ?: return@post
             val transportControls = controller.transportControls
+            
+            if (cmd.startsWith("SEEK:")) {
+                val posStr = cmd.removePrefix("SEEK:")
+                val pos = posStr.toLongOrNull()
+                if (pos != null) {
+                    transportControls.seekTo(pos)
+                }
+                return@post
+            }
+
             when (cmd) {
                 "TOGGLE_PLAY" -> {
                     if (controller.playbackState?.state == PlaybackState.STATE_PLAYING) {

Windows/Services/INetworkService.cs

@@ -30,5 +30,6 @@ public interface INetworkService
     void StopListening();
     Task SendCommandAsync(string command);
     Task SendCommandToEndpointAsync(string command, System.Net.IPEndPoint endpoint);
+    Task SendSeekAsync(long positionMs);
     void DisconnectLocal();
 }

Windows/Services/ISmtcService.cs

@@ -8,6 +8,7 @@ public interface ISmtcService
     event EventHandler PausePressed;
     event EventHandler NextPressed;
     event EventHandler PreviousPressed;
+    event EventHandler<double> SeekRequested;
 
     void Initialize();
     void UpdateMediaState(string title, string artist, string album, bool isPlaying, double position, double duration, string albumArtBase64 = "");

Windows/Services/NetworkService.cs

@@ -228,6 +228,11 @@ public async Task SendCommandAsync(string command)
         }
     }
 
+    public async Task SendSeekAsync(long positionMs)
+    {
+        await SendCommandAsync($"SEEK:{positionMs}");
+    }
+
     public async Task SendCommandToEndpointAsync(string command, IPEndPoint endpoint)
     {
         if (_dataClient != null)

Windows/Services/SmtcService.cs

@@ -13,6 +13,7 @@ public class SmtcService : ISmtcService
     public event EventHandler? PausePressed;
     public event EventHandler? NextPressed;
     public event EventHandler? PreviousPressed;
+    public event EventHandler<double>? SeekRequested;
 
     public void Initialize()
     {
@@ -25,10 +26,17 @@ public void Initialize()
         _smtc.IsPauseEnabled = true;
         _smtc.IsNextEnabled = true;
         _smtc.IsPreviousEnabled = true;
+        
+        _smtc.PlaybackPositionChangeRequested += Smtc_PlaybackPositionChangeRequested;
 
         _smtc.ButtonPressed += Smtc_ButtonPressed;
     }
 
+    private void Smtc_PlaybackPositionChangeRequested(SystemMediaTransportControls sender, PlaybackPositionChangeRequestedEventArgs args)
+    {
+        SeekRequested?.Invoke(this, args.RequestedPlaybackPosition.TotalMilliseconds);
+    }
+
     private void Smtc_ButtonPressed(SystemMediaTransportControls sender, SystemMediaTransportControlsButtonPressedEventArgs args)
     {
         switch (args.Button)

Windows/ViewModels/PlayerViewModel.cs

@@ -70,6 +70,7 @@ public PlayerViewModel(INetworkService networkService, ISmtcService smtcService,
         _smtcService.PausePressed += async (s, e) => await PlayPauseCommand.ExecuteAsync(null);
         _smtcService.NextPressed += async (s, e) => await NextCommand.ExecuteAsync(null);
         _smtcService.PreviousPressed += async (s, e) => await PreviousCommand.ExecuteAsync(null);
+        _smtcService.SeekRequested += async (s, position) => await SeekCommand.ExecuteAsync(position);
 
         DevicesVM.ActiveDeviceChanged += DevicesVM_ActiveDeviceChanged;
 
@@ -235,6 +236,21 @@ private async Task Previous()
         await _networkService.SendCommandAsync("PREV");
     }
 
+    [RelayCommand]
+    private async Task Seek(double position)
+    {
+        long posMs = (long)position;
+        await _networkService.SendSeekAsync(posMs);
+        
+        // Optimistically update position
+        _basePosition = position;
+        _lastUpdateTime = DateTime.Now;
+        CurrentPosition = position;
+        FormattedPosition = FormatTime(position);
+        Media.Position = position;
+        _smtcService.UpdateTimeline(position, Media.Duration);
+    }
+
     private void ResetState()
     {
         Media = new MediaState();

Windows/Views/PlayerPage.xaml

@@ -3,9 +3,9 @@
     xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
     xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
     xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
+    xmlns:labs="using:CommunityToolkit.WinUI.Controls"
     xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
     xmlns:models="using:CarpeCast.Models"
-    xmlns:labs="using:CommunityToolkit.WinUI.Controls"
     Background="Transparent"
     mc:Ignorable="d">
 
@@ -19,16 +19,14 @@
                 <Border>
                     <Border.Background>
                         <LinearGradientBrush StartPoint="0,0" EndPoint="0,1">
-                            <GradientStop Offset="0.0" Color="#FFFFFFFF" />
-                            <GradientStop Offset="0.5" Color="#FFFFFFFF" />
-                            <GradientStop Offset="1.0" Color="#00FFFFFF" />
+                            <GradientStop Offset="0.25" Color="#CCFFFFFF" />
+                            <GradientStop Offset="0.5" Color="#66FFFFFF" />
+                            <GradientStop Offset="0.75" Color="#00FFFFFF" />
                         </LinearGradientBrush>
                     </Border.Background>
                 </Border>
             </labs:OpacityMaskView.OpacityMask>
-            <Image
-                Source="{x:Bind ViewModel.AlbumArtImage, Mode=OneWay}"
-                Stretch="UniformToFill" />
+            <Image Source="{x:Bind ViewModel.AlbumArtImage, Mode=OneWay}" Stretch="UniformToFill" />
         </labs:OpacityMaskView>
 
         <!--  Placeholder Icon  -->
@@ -98,10 +96,13 @@
 
                 <!--  Progress  -->
                 <StackPanel Spacing="8">
-                    <ProgressBar
+                    <Slider
+                        x:Name="ProgressSlider"
                         HorizontalAlignment="Stretch"
+                        IsThumbToolTipEnabled="False"
                         Maximum="{x:Bind ViewModel.CurrentDuration, Mode=OneWay}"
-                        Value="{x:Bind ViewModel.CurrentPosition, Mode=OneWay}" />
+                        Value="{x:Bind ViewModel.CurrentPosition, Mode=OneWay}"
+                        ValueChanged="ProgressSlider_ValueChanged" />
                     <Grid>
                         <TextBlock
                             HorizontalAlignment="Left"

Windows/Views/PlayerPage.xaml.cs

@@ -1,4 +1,4 @@
-using Microsoft.UI.Xaml.Controls;
+using Microsoft.UI.Xaml.Controls;
 using Microsoft.Extensions.DependencyInjection;
 using CarpeCast.ViewModels;
 
@@ -15,4 +15,15 @@ public PlayerPage()
 
         ViewModel.StartNetworking();
     }
+
+    private void ProgressSlider_ValueChanged(object sender, Microsoft.UI.Xaml.Controls.Primitives.RangeBaseValueChangedEventArgs e)
+    {
+        if (ViewModel == null) return;
+        
+        // Ignore programmatic updates from the timer or SeekCommand itself
+        if (System.Math.Abs(e.NewValue - ViewModel.CurrentPosition) > 1.0)
+        {
+            ViewModel.SeekCommand.Execute(e.NewValue);
+        }
+    }
 }

task.md

@@ -0,0 +1,10 @@
+# Task Checklist: Implement Timeline Seek Control
+
+## Protocol
+- [ ] Add `SEEK:<position_ms>` command format to the UDP command protocol.
+
+## Windows Subagent
+- [x] Update `PlayerViewModel.cs`: Add `SeekCommand` (ICommand) to send `SEEK:<position_ms>` via NetworkService.
+- [x] Update `NetworkService.cs`: Add a method to send `SEEK:<position_ms>` to the active device.
+- [x] Update `PlayerPage.xaml`: Replace `ProgressBar` with a `Slider` representing progress in milliseconds. Bind it to the ViewModel and use `SeekCommand`.
+- [x] Update `SmtcService.cs`: Enable `IsPositionEnabled` in SMTC and listen for `PositionChangeRequested` to trigger a seek.