[Editor API] - Added function to assign a data context (view model) t…

…o the current hosted control without knowing the type of control or type of view model.

Tools/Editor/Gorgon.Editor.API/Properties/Resources.resx

@@ -368,4 +368,10 @@ These platforms are incompatible and cannot be mixed.</value>
     <value>The file '{0}' already exists.
 Would you like to overwrite it?</value>
   </data>
+  <data name="GOREDIT_ERR_HOSTED_CTL_NOT_DATACONTEXT" xml:space="preserve">
+    <value>The hosted control '{0}' does not accept data contexts.</value>
+  </data>
+  <data name="GOREDIT_ERR_INVALID_DATACONTEXT_TYPE" xml:space="preserve">
+    <value>The data context type '{0}' cannot be used with the hosted control.</value>
+  </data>
 </root>

Tools/Editor/Gorgon.Editor.API/UI/ViewFactory.cs

@@ -96,11 +96,6 @@ public static void Unregister<T>()
         /// </remarks>
         public static void AssignViewModel(IViewModel viewModel, Control control)
         {
-            if (viewModel is null)
-            {
-                throw new ArgumentNullException(nameof(viewModel));
-            }
-
             if (control is null)
             {
                 throw new ArgumentNullException(nameof(control));
@@ -119,6 +114,37 @@ public static void AssignViewModel(IViewModel viewModel, Control control)
             method?.Invoke(control, new[] { viewModel });
         }
 
+        /// <summary>
+        /// Function to retrieve the view model assigned to a control.
+        /// </summary>
+        /// <param name="control">The control to evaluate.</param>
+        /// <exception cref="ArgumentNullException">Thrown when the <paramref name="control"/> parameter is <b>null</b>.</exception>
+        /// <exception cref="InvalidCastException">Thrown if the <paramref name="control"/> parameter does not implement <see cref="IDataContext{T}"/>.</exception>
+        /// <remarks>
+        /// <para>
+        /// This will return the view model assigned to the specified <paramref name="control"/>. If the control does not implement <see cref="IDataContext{T}"/>, then an exception will be thrown.
+        /// </para>
+        /// </remarks>
+        public static IViewModel GetViewModel(Control control)
+        {
+            if (control is null)
+            {
+                throw new ArgumentNullException(nameof(control));
+            }
+
+            Type dataContextType = typeof(IDataContext<>);
+            Type controlType = control.GetType();
+            Type controlInterface = controlType.GetInterface(dataContextType.FullName);
+
+            if (controlInterface is null)
+            {
+                throw new InvalidCastException(string.Format(Resources.GOREDIT_ERR_HOSTED_CTL_NOT_DATACONTEXT, control.Name));
+            }
+
+            PropertyInfo property = controlInterface.GetProperty("DataContext");
+            return property?.GetValue(control) as IViewModel;
+        }
+
         /// <summary>
         /// Function to determine if the view model type has a view registration.
         /// </summary>

Tools/Editor/Gorgon.Editor.API/UI/Views/ContentBaseControl.cs

@@ -204,6 +204,15 @@ public event EventHandler<DragEventArgs> BubbleDragDrop
         #endregion
 
         #region Properties.
+        /// <summary>
+        /// Property to return the currently hosted panel in the <see cref="HostPanelControls"/>.
+        /// </summary>
+        protected Control CurrentHostedPanel
+        {
+            get;
+            private set;
+        }
+
         /// <summary>
         /// Property to set or return the idle method for rendering on the control.
         /// </summary>
@@ -461,6 +470,8 @@ protected void ShowHostedPanel(Control control)
                 PanelHostControls.Visible = PanelHost.Visible = true;
                 control.Visible = true;
                 PanelHostControls.AutoScrollMinSize = new Size(0, control.Height);
+
+                CurrentHostedPanel = control;
             }
             finally
             {
@@ -539,7 +550,48 @@ protected void HideHostedPanels()
                 control.Visible = false;
             }
 
-            PanelHost.Visible = PanelHostControls.Visible = false;            
+            PanelHost.Visible = PanelHostControls.Visible = false;
+
+            CurrentHostedPanel = null;
+        }
+
+        /// <summary>
+        /// Function to assign a data context to the <see cref="CurrentHostedPanel"/>.
+        /// </summary>
+        /// <param name="dataContext">The data context to assign.</param>        
+        /// <param name="overrideCurrentDc"><b>true</b> to replace any non-null data context if present, or <b>false</b> to leave the current data context in place.</param>
+        /// <exception cref="InvalidCastException">Thrown when the <see cref="CurrentHostedPanel"/> does not accept the type of data context represented by <paramref name="dataContext"/>.
+        /// <para>-or-</para>
+        /// <para>Thrown if the <see cref="CurrentHostedPanel"/> does not implement <see cref="IDataContext{T}"/>.</para>
+        /// </exception>
+        /// <remarks>
+        /// <para>
+        /// This method is used to assign an instance of a data context to the hosted panel in the <see cref="HostPanelControls"/>. If the panel does not implement <see cref="IDataContext{T}"/>, or the type of data 
+        /// context does not match the type of data context the control was built for, an exception will be thrown.
+        /// </para>
+        /// </remarks>
+        protected void AssignDataContextToHostedPanel(IViewModel dataContext, bool overrideCurrentDc)
+        {
+            if (CurrentHostedPanel is null)
+            {
+                return;
+            }
+
+            Type dataContextType = typeof(IDataContext<>);
+            Type controlType = CurrentHostedPanel.GetType();
+            Type controlInterface = controlType.GetInterface(dataContextType.FullName);
+
+            if (controlInterface is null)
+            {
+                throw new InvalidCastException(string.Format(Resources.GOREDIT_ERR_HOSTED_CTL_NOT_DATACONTEXT, CurrentHostedPanel.Name));
+            }
+
+            if ((!overrideCurrentDc) && (ViewFactory.GetViewModel(CurrentHostedPanel) is not null))
+            {
+                return;
+            }
+
+            ViewFactory.AssignViewModel(dataContext, CurrentHostedPanel);
         }
 
         /// <summary>