From a17926d02e58e8bb94f68f3d374cebeca407db0d Mon Sep 17 00:00:00 2001
From: Markus Ewald <cygon@nuclex.org>
Date: Mon, 11 Feb 2019 18:05:06 +0000
Subject: [PATCH] ViewControl and ViewForm were not actually reacting when
 their data context changed -- fixed; view models can now delay their search
 for a main window (needed to synchronize change notifications to the main
 threads because of those shitty WinForms controls); WindowManager now accepts
 ...Page as a postfix for a view name, too

git-svn-id: file:///srv/devel/repo-conversion/nuwi@48 d2e56fa2-650e-0410-a79f-9358c0239efd
---
 Nuclex.Windows.Forms (net-4.0).csproj  |   5 +-
 Source/LateCheckedSynchronizer.cs      | 137 +++++++++++++++++++++++++
 Source/ViewModels/ThreadedAction.cs    |  38 +++----
 Source/ViewModels/ThreadedViewModel.cs |  33 ++----
 Source/Views/IView.cs                  |   4 +
 Source/Views/ViewControl.cs            |   2 +
 Source/Views/ViewForm.cs               |   2 +
 Source/WindowManager.cs                |   2 +
 8 files changed, 171 insertions(+), 52 deletions(-)
 create mode 100644 Source/LateCheckedSynchronizer.cs

diff --git a/Nuclex.Windows.Forms (net-4.0).csproj b/Nuclex.Windows.Forms (net-4.0).csproj
index 37d31d3..e57c2cb 100644
--- a/Nuclex.Windows.Forms (net-4.0).csproj	
+++ b/Nuclex.Windows.Forms (net-4.0).csproj	
@@ -59,6 +59,7 @@
     <Compile Include="Source\AutoBinding\IAutoBinder.cs" />
     <Compile Include="Source\CommonDialogs\CommonDialogManager.cs" />
     <Compile Include="Source\CommonDialogs\ICommonDialogService.cs" />
+    <Compile Include="Source\LateCheckedSynchronizer.cs" />
     <Compile Include="Source\Messages\IMessageService.cs" />
     <Compile Include="Source\Messages\MessageEventArgs.cs" />
     <Compile Include="Source\Messages\MessageEventArgs.Test.cs">
@@ -154,7 +155,9 @@
       <Link>Foundation.snk</Link>
     </None>
   </ItemGroup>
-  <ItemGroup />
+  <ItemGroup>
+    <Folder Include="Resources\" />
+  </ItemGroup>
   <Import Project="$(MSBuildToolsPath)\Microsoft.CSharp.targets" />
   <!-- To modify your build process, add your task inside one of the targets below and uncomment it. 
        Other similar extension points exist, see Microsoft.Common.targets.
diff --git a/Source/LateCheckedSynchronizer.cs b/Source/LateCheckedSynchronizer.cs
new file mode 100644
index 0000000..a5fb49b
--- /dev/null
+++ b/Source/LateCheckedSynchronizer.cs
@@ -0,0 +1,137 @@
+using System;
+using System.ComponentModel;
+using System.Windows.Forms;
+
+namespace Nuclex.Windows.Forms {
+
+  /// <summary>
+  ///   Proxy stand-in to delay checking for the main window until it has been created
+  /// </summary>
+  /// <remarks>
+  ///   <para>
+  ///     The issue: when the view model for the main window is created, the main window
+  ///     may only exist as a .NET object, without the underlying operating system window
+  ///     (done in <see cref="System.Windows.Forms.Control.CreateControl" /> checkable via
+  ///     <see cref="System.Windows.Forms.Control.IsHandleCreated" />). Not only will things
+  ///     like <see cref="System.Windows.Forms.Control.Invoke(Delegate)" /> fail, we can't
+  ///     even locate the main window at that stage.
+  ///   </para>
+  ///   <para>
+  ///     Thus, if the main window cannot be found at the time a view model is created,
+  ///     this late-checking synchronizer will jump into its place and re-check for
+  ///     the main window only when something needs to be executed in the UI thread.
+  ///   </para>
+  /// </remarks>
+  class LateCheckedSynchronizer : ISynchronizeInvoke {
+
+    /// <summary>Initializes a new late-checked main window synchronizer</summary>
+    /// <param name="uiContextFoundCallback"></param>
+    public LateCheckedSynchronizer(Action<ISynchronizeInvoke> uiContextFoundCallback) {
+      this.uiContextFoundCallback = uiContextFoundCallback;
+    }
+
+    /// <summary>Finds the application's main window</summary>
+    /// <returns>Main window of the application or null if none has been created</returns>
+    /// <remarks>
+    ///   The application's main window, if it has been created yet
+    /// </remarks>
+    public static Form GetMainWindow() {
+      IntPtr mainWindowHandle = System.Diagnostics.Process.GetCurrentProcess().MainWindowHandle;
+
+      // We can get two things: a list of all open windows and the handle of
+      // the window that the process has registered as main window. Use the latter
+      // to pick the correct window from the former.
+      FormCollection openForms = Application.OpenForms;
+      int openFormCount = openForms.Count;
+      for(int index = 0; index < openFormCount; ++index) {
+        Form form = openForms[index];
+
+        IntPtr handle;
+        if(form.InvokeRequired) {
+          handle = (IntPtr)form.Invoke(new Func<Form, IntPtr>(getWindowHandle), form);
+        } else {
+          handle = getWindowHandle(form);
+        }
+        if(handle != IntPtr.Zero) {
+          if(handle == mainWindowHandle) {
+            return form;
+          }
+        }
+      }
+
+      // No matching main window found: use the first one in good faith or fail.
+      if(openFormCount > 0) {
+        return openForms[0];
+      } else {
+        return null;
+      }
+    }
+
+    /// <summary>Checks whether the calling thread needs to use Invoke()</summary>
+    public bool InvokeRequired {
+      get { return getMainWindowOrFail().InvokeRequired; }
+    }
+
+    /// <summary>Schedules a method to be run by the main UI thread</summary>
+    /// <param name="method">Method that will be scheduled to run</param>
+    /// <param name="args">Arguments that will be passed to the method</param>
+    /// <returns>An asynchronous result handle that can be used to track the call</returns>
+    public IAsyncResult BeginInvoke(Delegate method, object[] args) {
+      return getMainWindowOrFail().BeginInvoke(method, args);
+    }
+
+    /// <summary>Waits for a call scheduled on the main UI thread to complete</summary>
+    /// <param name="result">Asynchronous result handle returned by BeginInvoke()</param>
+    /// <returns>The value returned by the method ran in the main UI thread</returns>
+    public object EndInvoke(IAsyncResult result) {
+      return getMainWindowOrFail().EndInvoke(result);
+    }
+
+    /// <summary>Executes a method on the main UI thread and waits for it to complete</summary>
+    /// <param name="method">Method that will be run by the main UI thread</param>
+    /// <param name="arguments">Arguments that will be passed to the method</param>
+    /// <returns>The value returned by the method</returns>
+    public object Invoke(Delegate method, object[] arguments) {
+      return getMainWindowOrFail().Invoke(method, arguments);
+    }
+
+    /// <summary>Retrieves the application's current main window</summary>
+    /// <returns>The application's current main window</returns>
+    /// <remarks>
+    ///   If there is no main window, an exception will be thrown
+    /// </remarks>
+    private Form getMainWindowOrFail() {
+      Form mainWindow = GetMainWindow();
+      if(mainWindow == null) {
+        throw new InvalidOperationException(
+          "Could not schedule work for the UI thread because no WinForms UI main window " +
+          "was found. Create a main window first or specify the UI synchronization context " +
+          "explicitly to the view model."
+        );
+      }
+
+      if(this.uiContextFoundCallback != null) {
+        this.uiContextFoundCallback(mainWindow);
+        this.uiContextFoundCallback = null;
+      }
+
+      return mainWindow;
+    }
+
+    /// <summary>Returns a Form's window handle without forcing its creation</summary>
+    /// <param name="form">Form whose window handle will be returned</param>
+    /// <returns>The form's window handle of IntPtr.Zero if it has none</returns>
+    private static IntPtr getWindowHandle(Form form) {
+      if(form.IsHandleCreated) {
+        return form.Handle;
+      } else {
+        return IntPtr.Zero;
+      }
+    }
+
+    /// <summary>Called when the late-checked synchronizer finds the main window</summary>
+    private Action<ISynchronizeInvoke> uiContextFoundCallback;
+
+  }
+
+} // namespace Nuclex.Windows.Forms
diff --git a/Source/ViewModels/ThreadedAction.cs b/Source/ViewModels/ThreadedAction.cs
index bd73231..476f627 100644
--- a/Source/ViewModels/ThreadedAction.cs
+++ b/Source/ViewModels/ThreadedAction.cs
@@ -93,7 +93,10 @@ namespace Nuclex.Windows.Forms.ViewModels {
     /// <summary>Initializes a threaded action that uses its own thread runner</summary>
     public ThreadedAction(ISynchronizeInvoke uiContext = null) : this() {
       if(uiContext == null) {
-        this.uiContext = getMainWindow();
+        this.uiContext = LateCheckedSynchronizer.GetMainWindow();
+        if(this.uiContext == null) {
+          this.uiContext = new LateCheckedSynchronizer(updateUiContext);
+        }
       } else {
         this.uiContext = uiContext;
       }
@@ -112,7 +115,10 @@ namespace Nuclex.Windows.Forms.ViewModels {
       ThreadedViewModel viewModel, ISynchronizeInvoke uiContext = null
     ) : this() {
       if(uiContext == null) {
-        this.uiContext = getMainWindow();
+        this.uiContext = LateCheckedSynchronizer.GetMainWindow();
+        if(this.uiContext == null) {
+          this.uiContext = new LateCheckedSynchronizer(updateUiContext);
+        }
       } else {
         this.uiContext = uiContext;
       }
@@ -350,30 +356,10 @@ namespace Nuclex.Windows.Forms.ViewModels {
       this.uiContext.Invoke(this.reportErrorDelegate, new object[1] { exception });
     }
 
-    /// <summary>Finds the application's main window</summary>
-    /// <returns>Main window of the application</returns>
-    private static Form getMainWindow() {
-      IntPtr mainWindowHandle = System.Diagnostics.Process.GetCurrentProcess().MainWindowHandle;
-
-      // We can get two things: a list of all open windows and the handle of
-      // the window that the process has registered as main window. Use the latter
-      // to pick the correct window from the former.
-      FormCollection openForms = Application.OpenForms;
-      int openFormCount = openForms.Count;
-      for(int index = 0; index < openFormCount; ++index) {
-        if(openForms[index].IsHandleCreated) {
-          if(openForms[index].Handle == mainWindowHandle) {
-            return openForms[index];
-          }
-        }
-      }
-
-      // No matching main window found: use the first one in good faith or fail.
-      if(openFormCount > 0) {
-        return openForms[0];
-      } else {
-        return null;
-      }
+    /// <summary>Sets the UI context that will be used by the threaded action</summary>
+    /// <param name="uiContext">The UI context the threaded action will use</param>
+    private void updateUiContext(ISynchronizeInvoke uiContext) {
+      this.uiContext = uiContext;
     }
 
     /// <summary>Synchronization context of the thread in which the view runs</summary>
diff --git a/Source/ViewModels/ThreadedViewModel.cs b/Source/ViewModels/ThreadedViewModel.cs
index c6a18f4..06a4ed0 100644
--- a/Source/ViewModels/ThreadedViewModel.cs
+++ b/Source/ViewModels/ThreadedViewModel.cs
@@ -64,7 +64,10 @@ namespace Nuclex.Windows.Forms.ViewModels {
     /// </param>
     protected ThreadedViewModel(ISynchronizeInvoke uiContext = null) {
       if(uiContext == null) {
-        this.uiContext = getMainWindow();
+        this.uiContext = LateCheckedSynchronizer.GetMainWindow();
+        if(this.uiContext == null) {
+          this.uiContext = new LateCheckedSynchronizer(updateUiContext);
+        }
       } else {
         this.uiContext = uiContext;
       }
@@ -208,30 +211,10 @@ namespace Nuclex.Windows.Forms.ViewModels {
       this.uiContext.Invoke(this.reportErrorDelegate, new object[1] { exception });
     }
 
-    /// <summary>Finds the application's main window</summary>
-    /// <returns>Main window of the application</returns>
-    private static Form getMainWindow() {
-      IntPtr mainWindowHandle = System.Diagnostics.Process.GetCurrentProcess().MainWindowHandle;
-
-      // We can get two things: a list of all open windows and the handle of
-      // the window that the process has registered as main window. Use the latter
-      // to pick the correct window from the former.
-      FormCollection openForms = Application.OpenForms;
-      int openFormCount = openForms.Count;
-      for(int index = 0; index < openFormCount; ++index) {
-        if(openForms[index].IsHandleCreated) {
-          if(openForms[index].Handle == mainWindowHandle) {
-            return openForms[index];
-          }
-        }
-      }
-
-      // No matching main window found: use the first one in good faith or fail.
-      if(openFormCount > 0) {
-        return openForms[0];
-      } else {
-        return null;
-      }
+    /// <summary>Sets the UI context that will be used by the threaded action</summary>
+    /// <param name="uiContext">The UI context the threaded action will use</param>
+    private void updateUiContext(ISynchronizeInvoke uiContext) {
+      this.uiContext = uiContext;
     }
 
     /// <summary>An array of zero objects</summary>
diff --git a/Source/Views/IView.cs b/Source/Views/IView.cs
index 67221f1..202498c 100644
--- a/Source/Views/IView.cs
+++ b/Source/Views/IView.cs
@@ -32,6 +32,10 @@ namespace Nuclex.Windows.Forms.Views {
     /// </remarks>
     object DataContext { get; set; }
 
+    // Whether the view owns its view model and it needs to be disposed after
+    // the view ceases to exist
+    //bool IsOwnedByView { get; set; }
+
   }
 
 } // namespace Nuclex.Windows.Forms.Views
diff --git a/Source/Views/ViewControl.cs b/Source/Views/ViewControl.cs
index f86f4bd..47b6adc 100644
--- a/Source/Views/ViewControl.cs
+++ b/Source/Views/ViewControl.cs
@@ -72,7 +72,9 @@ namespace Nuclex.Windows.Forms.Views {
       get { return this.dataContext; }
       set {
         if(value != this.dataContext) {
+          object oldDataContext = this.dataContext;
           this.dataContext = value;
+          OnDataContextChanged(this, oldDataContext, value);
         }
       }
     }
diff --git a/Source/Views/ViewForm.cs b/Source/Views/ViewForm.cs
index 4238ebf..33daa65 100644
--- a/Source/Views/ViewForm.cs
+++ b/Source/Views/ViewForm.cs
@@ -72,7 +72,9 @@ namespace Nuclex.Windows.Forms.Views {
       get { return this.dataContext; }
       set {
         if(value != this.dataContext) {
+          object oldDataContext = this.dataContext;
           this.dataContext = value;
+          OnDataContextChanged(this, oldDataContext, value);
         }
       }
     }
diff --git a/Source/WindowManager.cs b/Source/WindowManager.cs
index 903169e..dfb80ba 100644
--- a/Source/WindowManager.cs
+++ b/Source/WindowManager.cs
@@ -260,6 +260,7 @@ namespace Nuclex.Windows.Forms {
         viewType = findBestMatch(
           namespaceTypes,
           viewName + "View",
+          viewName + "Page",
           viewName + "Form",
           viewName + "Window",
           viewName + "Dialog",
@@ -272,6 +273,7 @@ namespace Nuclex.Windows.Forms {
           viewType = findBestMatch(
             exportedTypes,
             viewName + "View",
+            viewName + "Page",
             viewName + "Form",
             viewName + "Window",
             viewName + "Dialog",