Started implementing logic behind the timeline UI

src/Artemis.UI/Screens/Module/ProfileEditor/LayerProperties/Timeline/PropertyTimelineViewModel.cs

@@ -0,0 +1,29 @@
+using System;
+using System.Linq;
+using Stylet;
+
+namespace Artemis.UI.Screens.Module.ProfileEditor.LayerProperties.Timeline
+{
+    public class PropertyTimelineViewModel : PropertyChangedBase
+    {
+        public PropertyTimelineViewModel(LayerPropertiesViewModel layerPropertiesViewModel)
+        {
+            LayerPropertiesViewModel = layerPropertiesViewModel;
+            RailItemViewModels = new BindableCollection<PropertyTrackViewModel>();
+        }
+
+        public LayerPropertiesViewModel LayerPropertiesViewModel { get; }
+
+        public double Width { get; set; }
+        public BindableCollection<PropertyTrackViewModel> RailItemViewModels { get; set; }
+
+        public void UpdateEndTime()
+        {
+            // End time is the last keyframe + 10 sec
+            var lastKeyFrame = RailItemViewModels.SelectMany(r => r.KeyframeViewModels).OrderByDescending(t => t.Keyframe.Position).FirstOrDefault();
+            var endTime = lastKeyFrame?.Keyframe.Position.Add(new TimeSpan(0, 0, 0, 10)) ?? TimeSpan.FromSeconds(10);
+
+            Width = endTime.TotalSeconds * LayerPropertiesViewModel.PixelsPerSecond;
+        }
+    }
+}