LT-20849: Refresh Baseline on Text switch if VScroll changes

Src/Common/SimpleRootSite/SimpleRootSite.cs

@@ -1626,6 +1626,14 @@ public bool IsHScrollVisible
 			get { return WantHScroll && AutoScrollMinSize.Width > Width; }
 		}
 
+		/// <summary>
+		/// We want to allow clients to tell whether we are showing the vertical scroll bar.
+		/// </summary>
+		public bool IsVScrollVisible
+		{
+			get { return VScroll; }
+		}
+
 		/// -----------------------------------------------------------------------------------
 		/// <summary>
 		/// Root site slaves sometimes need to suppress the effects of OnSizeChanged.

Src/LexText/Interlinear/RawTextPane.cs

@@ -43,6 +43,16 @@ public class RawTextPane : RootSite, IInterlinearTabControl, IHandleBookmark
 
 		private string m_currentTool = "";
 
+		public bool PreviousShowVScroll;
+
+		private void RefreshIfNecessary(object sender, LayoutEventArgs e)
+		{
+			bool showVScroll = ((SimpleRootSite)m_rootb?.Site)?.IsVScrollVisible ?? false;
+			Layout -= RefreshIfNecessary;
+			if (showVScroll != PreviousShowVScroll)
+				RootBox?.Reconstruct();
+		}
+
 		public string CurrentTool
 		{
 			get { return m_currentTool; }
@@ -308,6 +318,12 @@ public override void OnPropertyChanged(string name)
 					wsBefore = SelectionHelper.GetWsOfEntireSelection(m_rootb.Selection);
 			}
 
+			if (name == "ActiveClerkSelectedObject")
+			{
+				Layout += RefreshIfNecessary;
+				PreviousShowVScroll = ((SimpleRootSite)m_rootb?.Site)?.IsVScrollVisible ?? false;
+			}
+
 			base.OnPropertyChanged(name);
 			bool newVal; // used in two cases below
 			switch (name)