Make tab content lazily constructed

3 files changed, 84 insertions, 4 deletions

diff --git a/main/src/tools/ExtensionTools/Application.cs b/main/src/tools/ExtensionTools/Application.cs
index 23b7cf73b1..5d86c23fda 100644
--- a/main/src/tools/ExtensionTools/Application.cs
+++ b/main/src/tools/ExtensionTools/Application.cs
@@ -24,6 +24,7 @@
 // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 // THE SOFTWARE.
 using System;
+using System.Collections.Generic;
 using System.IO;
 using System.Reflection;
 using System.Threading;
@@ -74,13 +75,20 @@ namespace MonoDevelop.ExtensionTools
 
 		static Widget CreateWindowContent ()
 		{
-			var nb = new Notebook ();
+			var nb = new LazyNotebook ();
 
-			nb.Add (new AddinListWidget (), "List");
-			nb.Add (new AddinDependencyTreeWidget (), "Dependency Tree");
-			nb.Add (new ExtensionPointsWidget (), "Extension Points");
+			foreach (var (widgetFunc, title) in GetTabs ()) {
+				nb.Add (widgetFunc, title);
+			}
 
 			return nb;
 		}
+
+		static IEnumerable<(Func<Widget> widgetFunc, string title)> GetTabs ()
+		{
+			yield return (() => new AddinListWidget (), "List");
+			yield return (() => new AddinDependencyTreeWidget (), "Dependency Tree");
+			yield return (() => new ExtensionPointsWidget (), "Extension Points");
+		}
 	}
 }
diff --git a/main/src/tools/ExtensionTools/ExtensionTools.csproj b/main/src/tools/ExtensionTools/ExtensionTools.csproj
index 7cc890870f..f263e9b78c 100644
--- a/main/src/tools/ExtensionTools/ExtensionTools.csproj
+++ b/main/src/tools/ExtensionTools/ExtensionTools.csproj
@@ -28,6 +28,7 @@
     <Compile Include="AddinListWidget.cs" />
     <Compile Include="AddinRegistryExtensions.cs" />
     <Compile Include="ExtensionPointsWidget.cs" />
+    <Compile Include="LazyNotebook.cs" />
   </ItemGroup>
   <ItemGroup>
     <ProjectReference Include="..\..\core\MonoDevelop.Core\MonoDevelop.Core.csproj">
diff --git a/main/src/tools/ExtensionTools/LazyNotebook.cs b/main/src/tools/ExtensionTools/LazyNotebook.cs
new file mode 100644
index 0000000000..2f8c98e05b
--- /dev/null
+++ b/main/src/tools/ExtensionTools/LazyNotebook.cs
@@ -0,0 +1,71 @@
+//
+// LazyNotebook.cs
+//
+// Author:
+//       Marius Ungureanu <maungu@microsoft.com>
+//
+// Copyright (c) 2018 Microsoft Inc.
+//
+// Permission is hereby granted, free of charge, to any person obtaining a copy
+// of this software and associated documentation files (the "Software"), to deal
+// in the Software without restriction, including without limitation the rights
+// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+// copies of the Software, and to permit persons to whom the Software is
+// furnished to do so, subject to the following conditions:
+//
+// The above copyright notice and this permission notice shall be included in
+// all copies or substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+// THE SOFTWARE.
+using System;
+using Xwt;
+
+namespace MonoDevelop.ExtensionTools
+{
+	class LazyNotebook : Notebook
+	{
+		public void Add (Func<Widget> createWidget, string label)
+		{
+			var createWidgetChain = OnAdd (createWidget);
+			var widget = new LazyWidget (createWidgetChain);
+			Add (widget, label);
+		}
+
+		protected override void OnCurrentTabChanged (EventArgs e)
+		{
+			base.OnCurrentTabChanged (e);
+			Xwt.Application.TimeoutInvoke (0, () => {
+				Toolkit.NativeEngine.Invoke (() => {
+					var tab = Tabs [CurrentTabIndex];
+					var lazy = (LazyWidget)tab.Child;
+					lazy.CreateContent ();
+				});
+				return false;
+			});
+		}
+
+		protected virtual Func<Widget> OnAdd (Func<Widget> createWidget) => createWidget;
+
+		class LazyWidget : Widget
+		{
+			readonly Func<Widget> createWidget;
+
+			public LazyWidget (Func<Widget> createWidget)
+			{
+				this.createWidget = createWidget;
+			}
+
+			public void CreateContent ()
+			{
+				if (Content == null)
+					Content = createWidget ();
+			}
+		}
+	}
+}