feat: swap placement.

src/Ursa/Controls/Timeline/TimelineDisplayMode.cs

@@ -8,6 +8,12 @@ public enum TimelineDisplayMode
     Alternate,
 }
 
+/// <summary>
+/// Placement of timeline.
+/// Left means line is placed left to TimelineItem content.
+/// Right means line is placed right to TimelineItem content.
+/// Separate means line is placed between TimelineItem content and time.
+/// </summary>
 public enum TimelineItemDisplayMode
 {
     Left,

src/Ursa/Controls/Timeline/TimelineItem.cs

@@ -169,12 +169,12 @@ public class TimelineItem: HeaderedContentControl
         if (Mode == TimelineItemDisplayMode.Left)
         {
             max = Math.Max(max, time);
-            return (max, icon, 0);
+            return (0, icon, max);
         }
         if (Mode == TimelineItemDisplayMode.Right)
         {
             max = Math.Max(max, time);
-            return (0, icon, max);
+            return (max    , icon, 0);
         }
         if (Mode == TimelineItemDisplayMode.Separate)
         {