WIP: Defer node view loading to speed up opening times (and possibly UX) of large graphs.

src/DynamoCoreWpf/Commands/NoteCommands.cs

@@ -1,9 +1,11 @@
-using Dynamo.UI.Commands;
+using Dynamo.Controls;
+using Dynamo.UI.Commands;
+using Dynamo.Utilities;
 using Newtonsoft.Json;
 
 namespace Dynamo.ViewModels
 {
-    public partial class NoteViewModel
+    public partial class NoteViewModel: IWorkspaceElement
     {
         private DelegateCommand _selectCommand;
         [JsonIgnore]
@@ -93,5 +95,22 @@ public DelegateCommand UnpinFromNodeCommand
                 return unpinFromNodeCommand;
             }
         }
+
+        /// <summary>
+        /// This signifies if the note should be rendered
+        /// </summary>
+        [JsonIgnore]
+        public bool IsVisibleInCanvas
+        {
+            get => isVisibleInCanvas;
+            set
+            {
+                isVisibleInCanvas = value;
+                RaisePropertyChanged(nameof(isVisibleInCanvas));
+            }
+        }
+        private bool isVisibleInCanvas = false;
+
+        public Rect2D Rect => Model.Rect;
     }
 }

src/DynamoCoreWpf/Controls/DeferredContent.cs

@@ -0,0 +1,52 @@
+using System;
+using System.Windows;
+using System.Windows.Controls;
+
+namespace Dynamo.Controls
+{
+    /// <summary>
+    /// https://stackoverflow.com/a/26543731
+    /// </summary>
+    public class DeferredContent : ContentPresenter
+    {
+        public DataTemplate DeferredContentTemplate
+        {
+            get { return (DataTemplate)GetValue(DeferredContentTemplateProperty); }
+            set { SetValue(DeferredContentTemplateProperty, value); }
+        }
+
+        public static readonly DependencyProperty DeferredContentTemplateProperty =
+            DependencyProperty.Register("DeferredContentTemplate",
+            typeof(DataTemplate), typeof(DeferredContent), null);
+
+        public DeferredContent()
+        {
+            IsVisibleChanged += DeferredContent_IsVisibleChanged;
+        }
+
+        private void DeferredContent_IsVisibleChanged(object sender, DependencyPropertyChangedEventArgs e)
+        {
+            if (true.Equals(e.NewValue))
+            {
+                IsVisibleChanged -= DeferredContent_IsVisibleChanged;
+                Dispatcher.BeginInvoke(ShowDeferredContent);
+            }
+        }
+
+        public void ShowDeferredContent()
+        {
+            if (DeferredContentTemplate != null)
+            {
+                base.Content = DeferredContentTemplate.LoadContent();
+                RaiseDeferredContentLoaded();
+            }
+        }
+
+        private void RaiseDeferredContentLoaded()
+        {
+            DeferredContentLoaded?.Invoke(this, new RoutedEventArgs());
+        }
+
+        public event EventHandler<RoutedEventArgs> DeferredContentLoaded;
+    }
+}

src/DynamoCoreWpf/Controls/IWorkspaceElement.cs

@@ -0,0 +1,10 @@
+using Dynamo.Utilities;
+
+namespace Dynamo.Controls
+{
+    internal interface IWorkspaceElement
+    {
+        bool IsVisibleInCanvas { get; set; }
+        Rect2D Rect { get; }
+    }
+}

src/DynamoCoreWpf/DynamoCoreWpf.csproj

@@ -224,6 +224,7 @@
       <DependentUpon>InstalledPackagesControl.xaml</DependentUpon>
     </Compile>
     <Compile Include="Commands\ConnectorPinCommands.cs" />
+    <Compile Include="Controls\IWorkspaceElement.cs" />
     <Compile Include="Controls\NodeAutoCompleteSearchControl.xaml.cs">
       <DependentUpon>NodeAutoCompleteSearchControl.xaml</DependentUpon>
     </Compile>
@@ -455,6 +456,7 @@
       <DependentUpon>AboutWindow.xaml</DependentUpon>
     </Compile>
     <Compile Include="Views\CodeBlocks\CodeBlockEditor.cs" />
+    <Compile Include="Controls\DeferredContent.cs" />
     <Compile Include="Views\Core\ConnectorAnchorView.xaml.cs">
       <DependentUpon>ConnectorAnchorView.xaml</DependentUpon>
     </Compile>

src/DynamoCoreWpf/UI/Themes/Modern/DataTemplates.xaml

@@ -10,9 +10,15 @@
     <ResourceDictionary.MergedDictionaries>
         <ui:SharedResourceDictionary Source="{x:Static ui:SharedDictionaryManager.DynamoConvertersDictionaryUri}" />
     </ResourceDictionary.MergedDictionaries>
-
     <DataTemplate DataType="{x:Type viewModels:NodeViewModel}">
-        <controls:NodeView></controls:NodeView>
+        <controls:DeferredContent
+            Content="{x:Null}">
+            <controls:DeferredContent.DeferredContentTemplate>
+                <DataTemplate>
+                    <controls:NodeView />
+                </DataTemplate>
+            </controls:DeferredContent.DeferredContentTemplate>
+        </controls:DeferredContent>
     </DataTemplate>
 
     <DataTemplate DataType="{x:Type viewModels:NoteViewModel}">
@@ -27,4 +33,4 @@
         <nodes:AnnotationView></nodes:AnnotationView>
     </DataTemplate>
 
-</ResourceDictionary>
+</ResourceDictionary>

src/DynamoCoreWpf/ViewModels/Core/AnnotationViewModel.cs

@@ -6,6 +6,7 @@
 using System.Windows.Input;
 using System.Windows.Media;
 using Dynamo.Configuration;
+using Dynamo.Controls;
 using Dynamo.Graph;
 using Dynamo.Graph.Annotations;
 using Dynamo.Graph.Nodes;
@@ -20,7 +21,7 @@
 
 namespace Dynamo.ViewModels
 {
-    public class AnnotationViewModel : ViewModelBase
+    public class AnnotationViewModel : ViewModelBase, IWorkspaceElement
     {
         private AnnotationModel annotationModel;
         private IEnumerable<PortModel> originalInPorts;
@@ -371,6 +372,24 @@ public ObservableCollection<Configuration.StyleItem> GroupStyleList
                 RaisePropertyChanged(nameof(GroupStyleList));
             }
         }
+
+        /// <summary>
+        /// This signifies if the node should be rendered
+        /// </summary>
+        [JsonIgnore]
+        public bool IsVisibleInCanvas
+        {
+            get => isVisibleInCanvas;
+            set
+            {
+                isVisibleInCanvas = value;
+                RaisePropertyChanged(nameof(isVisibleInCanvas));
+            }
+        }
+        private bool isVisibleInCanvas = false;
+
+        public Rect2D Rect => AnnotationModel.Rect;
+
         #endregion
 
         #region Commands

src/DynamoCoreWpf/ViewModels/Core/NodeViewModel.cs

@@ -11,6 +11,7 @@
 using System.Windows.Controls.Primitives;
 using System.Windows.Media;
 using Dynamo.Configuration;
+using Dynamo.Controls;
 using Dynamo.Engine.CodeGeneration;
 using Dynamo.Graph;
 using Dynamo.Graph.Nodes;
@@ -20,6 +21,7 @@
 using Dynamo.Logging;
 using Dynamo.Models;
 using Dynamo.Selection;
+using Dynamo.Utilities;
 using Dynamo.Wpf.ViewModels.Core;
 using Newtonsoft.Json;
 using Point = System.Windows.Point;
@@ -31,7 +33,7 @@ namespace Dynamo.ViewModels
     /// Interaction logic for dynControl.xaml
     /// </summary>
 
-    public partial class NodeViewModel : ViewModelBase
+    public partial class NodeViewModel : ViewModelBase, IWorkspaceElement
     {
         #region delegates
         public delegate void SetToolTipDelegate(string message);
@@ -573,6 +575,23 @@ public bool NodeHoveringState
             }
         }
 
+        /// <summary>
+        /// This signifies if the node should be rendered
+        /// </summary>
+        [JsonIgnore]
+        public bool IsVisibleInCanvas
+        {
+            get => isVisibleInCanvas;
+            set
+            {
+                isVisibleInCanvas = value;
+                RaisePropertyChanged(nameof(isVisibleInCanvas));
+            }
+        }
+        private bool isVisibleInCanvas = false;
+
+        public Rect2D Rect => NodeModel.Rect;
+
         private bool isNodeNewlyAdded;
         private ImageSource imageSource;
         private string imgGlyphOneSource;

src/DynamoCoreWpf/ViewModels/Core/WorkspaceViewModel.cs

@@ -10,6 +10,7 @@
 using System.Windows.Data;
 using System.Windows.Input;
 using Dynamo.Configuration;
+using Dynamo.Controls;
 using Dynamo.Engine;
 using Dynamo.Graph;
 using Dynamo.Graph.Annotations;
@@ -533,6 +534,8 @@ internal GeometryScalingViewModel GeoScalingViewModel
             }
         }
 
+        private bool FinishedLoading = false;
+
         #endregion
 
         public WorkspaceViewModel(WorkspaceModel model, DynamoViewModel dynamoViewModel)
@@ -606,7 +609,9 @@ public WorkspaceViewModel(WorkspaceModel model, DynamoViewModel dynamoViewModel)
             foreach (NoteModel note in Model.Notes) Model_NoteAdded(note);
             foreach (AnnotationModel annotation in Model.Annotations) Model_AnnotationAdded(annotation);
             foreach (ConnectorModel connector in Model.Connectors) Connectors_ConnectorAdded(connector);
-
+
+            FinishedLoading = true;
+
             NodeAutoCompleteSearchViewModel = new NodeAutoCompleteSearchViewModel(DynamoViewModel)
             {
                 Visible = true
@@ -823,6 +828,11 @@ private void Model_NoteAdded(NoteModel note)
         {
             var viewModel = new NoteViewModel(this, note);
             Notes.Add(viewModel);
+
+            if (FinishedLoading)
+            {
+                viewModel.IsVisibleInCanvas = true;
+            }
         }
 
         private void Model_NoteRemoved(NoteModel note)
@@ -845,6 +855,11 @@ private void Model_AnnotationAdded(AnnotationModel annotation)
         {
             var viewModel = new AnnotationViewModel(this, annotation);
             Annotations.Add(viewModel);
+
+            if (FinishedLoading)
+            {
+                viewModel.IsVisibleInCanvas = true;
+            }
         }
 
         private void Model_AnnotationRemoved(AnnotationModel annotation)
@@ -908,12 +923,21 @@ void Model_NodeAdded(NodeModel node)
             var nodeViewModel = new NodeViewModel(this, node);
             nodeViewModel.SnapInputEvent += nodeViewModel_SnapInputEvent;
             nodeViewModel.NodeLogic.Modified += OnNodeModified;
+
             lock (Nodes)
             {
                 Nodes.Add(nodeViewModel);
             }
             if (nodeViewModel.ErrorBubble != null)
+            {
+                nodeViewModel.ErrorBubble.IsVisibleInCanvas = FinishedLoading;
                 Errors.Add(nodeViewModel.ErrorBubble);
+            }
+
+            if (FinishedLoading)
+            {
+                nodeViewModel.IsVisibleInCanvas = true;
+            }
 
             PostNodeChangeActions();
         }
@@ -1862,7 +1886,36 @@ internal IEnumerable<ViewModelBase> GetViewModelsInternal(IEnumerable<Guid> mode
             return foundModels;
         }
 
-
+        internal void UpdateWorkspaceElementVisibility(double visibleWidth, double visibleHeight)
+        {
+            var width = visibleWidth / Zoom;
+            var height = visibleHeight / Zoom;
+            var left = -X / Zoom;
+            var top = -Y / Zoom;
+
+            var visibleRect = new Rect2D(left, top, width, height);
+            var itemsToTest = Nodes.Cast<IWorkspaceElement>()
+                                   .Concat(Notes)
+                                   .Concat(Annotations);
+
+            foreach (var item in itemsToTest)
+            {
+                item.IsVisibleInCanvas = visibleRect.IntersectsWith(item.Rect);
+
+                if (item is NodeViewModel nvm && item.IsVisibleInCanvas && nvm.ErrorBubble != null)
+                {
+                    nvm.ErrorBubble.IsVisibleInCanvas = true;
+                }
+            }
+
+#if DEBUG
+            var total = Nodes.Count + Notes.Count + Annotations.Count;
+            var hidden = Nodes.Count(n => !n.IsVisibleInCanvas) +
+                         Notes.Count(n => !n.IsVisibleInCanvas) +
+                         Annotations.Count(a => !a.IsVisibleInCanvas);
+            Debug.WriteLine($"{hidden}/{total} workspace elements hidden");
+#endif
+        }
     }
 
     public class ViewModelEventArgs : EventArgs

src/DynamoCoreWpf/ViewModels/Preview/InfoBubbleViewModel.cs

@@ -4,7 +4,9 @@
 using System.Linq;
 using System.Text.RegularExpressions;
 using System.Windows;
+using Dynamo.Controls;
 using Dynamo.Logging;
+using Dynamo.Utilities;
 using Dynamo.Wpf.ViewModels.Core;
 
 namespace Dynamo.ViewModels
@@ -26,7 +28,7 @@ public InfoBubbleEventArgs(Request request)
 
     public delegate void InfoBubbleEventHandler(object sender, InfoBubbleEventArgs e);
 
-    public partial class InfoBubbleViewModel : ViewModelBase
+    public partial class InfoBubbleViewModel : ViewModelBase, IWorkspaceElement
     {
         public enum Style
         {
@@ -444,7 +446,23 @@ public bool NodeWarningsIteratorVisible
         /// and cannot have their Width (or Visibility) set manually.
         /// </summary>
         public bool NodeErrorsIteratorVisible => GetMessagesOfStyle(NodeMessages, Style.Error).Count > 1;
-
+
+        /// <summary>
+        /// This signifies if the node should be rendered
+        /// </summary>
+        public bool IsVisibleInCanvas
+        {
+            get => isVisibleInCanvas;
+            set
+            {
+                isVisibleInCanvas = value;
+                RaisePropertyChanged(nameof(isVisibleInCanvas));
+            }
+        }
+        private bool isVisibleInCanvas = false;
+
+        public Rect2D Rect => default;
+
         #endregion
 
         #region Event Handlers

src/DynamoCoreWpf/Views/Core/WorkspaceView.xaml

@@ -185,6 +185,9 @@
                                 Value="{Binding Top}" />
                         <Setter Property="Panel.ZIndex"
                                 Value="{Binding ZIndex}" />
+                        <Setter
+                            Property="Visibility"
+                            Value="{Binding IsVisibleInCanvas, Converter={StaticResource BooleanToVisibilityConverter}, Mode=OneWay, FallbackValue=Visible}" />
                     </Style>
                 </ItemsControl.ItemContainerStyle>