[Ide] Let the references search be a child of the notebook

This is a partial fix for VSTS #750263, AtkCocoa needs to
support the right focus order, including an Action widget.

Author: sevoku

main/src/core/MonoDevelop.Ide/MonoDevelop.Ide.Projects/SelectReferenceDialog.cs

@@ -36,6 +36,7 @@
 using MonoDevelop.Components;
 using MonoDevelop.Components.Commands;
 using System.IO;
+using System.Runtime.InteropServices;
 
 namespace MonoDevelop.Ide.Projects
 {
@@ -157,16 +158,21 @@ TreeIter AddPackageReference (ProjectReference refInfo)
 			}
 			return refTreeStore.AppendValues (txt, secondaryTxt, GetTypeText (refInfo), refInfo.Reference, refInfo, ImageService.GetIcon ("md-package", IconSize.Dnd));
 		}
-		
+
+		[DllImport ("libgtk-win32-2.0-0.dll", CallingConvention = CallingConvention.Cdecl)]
+		private static extern void gtk_notebook_set_action_widget (IntPtr notebook, IntPtr widget, int packType);
+
 		public SelectReferenceDialog ()
 		{
 			Build ();
 
 			combinedBox = new CombinedBox ();
 			combinedBox.Show ();
 			mainBook = new Notebook ();
-			combinedBox.Add (mainBook);
-			alignment1.Add (combinedBox);
+
+			gtk_notebook_set_action_widget (mainBook.Handle, combinedBox.Handle, (int)PackType.End);
+
+			alignment1.Add (mainBook);
 			mainBook.ShowAll ();
 
 			filterEntry = combinedBox.FilterEntry;
@@ -538,22 +544,24 @@ protected override void OnRemoved (Widget widget)
 
 		protected override void OnSizeAllocated (Gdk.Rectangle allocation)
 		{
+			allocation.Y -= 2;
 			base.OnSizeAllocated (allocation);
 			RepositionFilter ();
 		}
 
 		protected override void OnSizeRequested (ref Requisition requisition)
 		{
-			if (Child != null)
-				requisition = Child.SizeRequest ();
-			requisition.Width += filterEntry.SizeRequest ().Width;
+			requisition = Child?.SizeRequest () ?? Requisition.Zero;
+			var entryRequest = filterEntry.SizeRequest ();
+			requisition.Width += entryRequest.Width;
+			requisition.Height = Math.Max (requisition.Height, entryRequest.Height);
 		}
 
 		void RepositionFilter ()
 		{
-			int w = filterEntry.SizeRequest ().Width;
-			int h = filterEntry.SizeRequest ().Height;
-			filterEntry.SizeAllocate (new Gdk.Rectangle (Allocation.Width - w - 1, 0, w, h));
+			var req = filterEntry.SizeRequest ();
+			int h = Math.Min (Allocation.Height, req.Height);
+			filterEntry.SizeAllocate (new Gdk.Rectangle (Allocation.Width - req.Width - 1, 0, req.Width, h));
 		}
 	}