Hack in V6 to draw an inactive Grasshopper document

InactiveGhDocDisplay.cs

using System;
using System.Collections.Generic;
using System.Drawing;
using Grasshopper.Kernel;
using Grasshopper.Kernel.Types;
using Rhino;
using Rhino.Commands;

namespace InactiveGhDocDisplay
{
  public class InactiveGhDocDisplayCommand : Command
  {
    bool _conduitsEnabled = false;

    public override string EnglishName => "InactiveGhDocDisplay";

    protected override Result RunCommand(RhinoDoc doc, RunMode mode)
    {
      _conduitsEnabled = !_conduitsEnabled; // toggle on/off
      if (_conduitsEnabled)
      {
        Rhino.Display.DisplayPipeline.CalculateBoundingBoxZoomExtents += DisplayPipeline_CalculateBoundingBoxZoomExtents;
        Rhino.Display.DisplayPipeline.CalculateBoundingBox += DisplayPipeline_CalculateBoundingBox;
        Rhino.Display.DisplayPipeline.PreDrawTransparentObjects += DisplayPipeline_PreDrawTransparentObjects;
      }
      else
      {
        Rhino.Display.DisplayPipeline.CalculateBoundingBoxZoomExtents -= DisplayPipeline_CalculateBoundingBoxZoomExtents;
        Rhino.Display.DisplayPipeline.CalculateBoundingBox -= DisplayPipeline_CalculateBoundingBox;
        Rhino.Display.DisplayPipeline.PreDrawTransparentObjects -= DisplayPipeline_PreDrawTransparentObjects;
      }

      RhinoApp.WriteLine($"Inactive GH Doc drawing enabled = {_conduitsEnabled}");
      doc.Views.Redraw();
      return Result.Success;
    }

    GH_Document GetInactiveDoc(bool buildCache)
    {
      int docCount = Grasshopper.Instances.DocumentServer.DocumentCount;
      if (docCount < 2)
        return null;
      var ghDoc = Grasshopper.Instances.DocumentServer[1];
      if( ghDoc != null && buildCache)
      {
        var field = ghDoc.GetType().GetField("m_drawList", System.Reflection.BindingFlags.Instance | System.Reflection.BindingFlags.NonPublic);
        if (field.GetValue(ghDoc) == null)
        {
          var createPreviewCaches = ghDoc.GetType().GetMethod("CreatePreviewCaches", System.Reflection.BindingFlags.Instance | System.Reflection.BindingFlags.NonPublic);
          if( createPreviewCaches != null)
          {
            createPreviewCaches.Invoke(ghDoc, null);
          }
        }
      }
      return ghDoc;
    }

    private void DisplayPipeline_PreDrawTransparentObjects(object sender, Rhino.Display.DrawEventArgs e)
    {
      var ghDoc = GetInactiveDoc(false);
      if (null == ghDoc || !ghDoc.PreviewBoundingBox.IsValid)
        return;

      var field = ghDoc.GetType().GetField("m_drawList", System.Reflection.BindingFlags.Instance | System.Reflection.BindingFlags.NonPublic);
      var drawList = field.GetValue(ghDoc) as List<IGH_PreviewObject>;
      if (null == drawList)
        return;

      var col0 = Color.FromArgb(ghDoc.PreviewColour.R, ghDoc.PreviewColour.G, ghDoc.PreviewColour.B);
      var col1 = Color.FromArgb(ghDoc.PreviewColourSelected.R, ghDoc.PreviewColourSelected.G, ghDoc.PreviewColourSelected.B);
      var mat0 = GH_Material.CreateStandardMaterial(ghDoc.PreviewColour);
      var mat1 = GH_Material.CreateStandardMaterial(ghDoc.PreviewColourSelected);
      int wireThickness = e.Display.DefaultCurveThickness;
      var constructors = typeof(GH_PreviewArgs).GetConstructors(System.Reflection.BindingFlags.Instance | System.Reflection.BindingFlags.NonPublic);
      var args0 = constructors[0].Invoke(new object[] {ghDoc, e.Display, e.Viewport, wireThickness, col0, col1, mat0, mat1, ghDoc.PreviewCurrentMeshParameters() }) as GH_PreviewArgs;
 
      // Draw all objects
      foreach(var item in drawList)
      {
        if (item.Hidden)
          continue;
        item.DrawViewportWires(args0);
      }

      foreach (var item in drawList)
      {
        if (item.Hidden)
          continue;
        item.DrawViewportMeshes(args0);
      }
    }

    private void DisplayPipeline_CalculateBoundingBox(object sender, Rhino.Display.CalculateBoundingBoxEventArgs e)
    {
      var ghDoc = GetInactiveDoc(true);
      if (null == ghDoc)
        return;
      e.IncludeBoundingBox(ghDoc.PreviewBoundingBox);
    }

    private void DisplayPipeline_CalculateBoundingBoxZoomExtents(object sender, Rhino.Display.CalculateBoundingBoxEventArgs e)
    {
      var ghDoc = GetInactiveDoc(true);
      if (null == ghDoc)
        return;
      e.IncludeBoundingBox(ghDoc.PreviewBoundingBox);
    }
  }
}