Added SelectedCellChangedEventArgs and tests

Terminal.Gui/Views/TableView.cs

@@ -179,7 +179,7 @@ namespace Terminal.Gui {
 				selectedColumn = Table == null ? 0 :  Math.Min (Table.Columns.Count - 1, Math.Max (0, value));
 
 				if(oldValue != selectedColumn)
-					OnSelectedCellChanged();
+					OnSelectedCellChanged(new SelectedCellChangedEventArgs(Table,oldValue,SelectedColumn,SelectedRow,SelectedRow));
 			} 
 		}
 
@@ -190,12 +190,12 @@ namespace Terminal.Gui {
 			get => selectedRow;
 			set {
 
-				var oldValue = selectedColumn;
+				var oldValue = selectedRow;
 
 				selectedRow =  Table == null ? 0 : Math.Min (Table.Rows.Count - 1, Math.Max (0, value));
 
 				if(oldValue != selectedRow)
-					OnSelectedCellChanged();
+					OnSelectedCellChanged(new SelectedCellChangedEventArgs(Table,SelectedColumn,SelectedColumn,oldValue,selectedRow));
 			}
 		}
 
@@ -217,7 +217,7 @@ namespace Terminal.Gui {
 		/// <summary>
 		/// This event is raised when the selected cell in the table changes.
 		/// </summary>
-		public event Action<EventArgs> SelectedCellChanged;
+		public event Action<SelectedCellChangedEventArgs> SelectedCellChanged;
 
 		/// <summary>
 		/// Initialzies a <see cref="TableView"/> class using <see cref="LayoutStyle.Computed"/> layout. 
@@ -715,9 +715,9 @@ namespace Terminal.Gui {
 		/// <summary>
 		/// Invokes the <see cref="SelectedCellChanged"/> event
 		/// </summary>
-		protected virtual void OnSelectedCellChanged()
+		protected virtual void OnSelectedCellChanged(SelectedCellChangedEventArgs args)
 		{
-			SelectedCellChanged?.Invoke(new EventArgs());
+			SelectedCellChanged?.Invoke(args);
 		}
 
 		/// <summary>
@@ -853,4 +853,61 @@ namespace Terminal.Gui {
 			X = x;
 		}
 	}
+
+	/// <summary>
+	/// Defines the event arguments for <see cref="TableView.SelectedCellChanged"/> 
+	/// </summary>
+	public class SelectedCellChangedEventArgs : EventArgs
+	{
+		/// <summary>
+		/// The current table to which the new indexes refer.  May be null e.g. if selection change is the result of clearing the table from the view
+		/// </summary>
+		/// <value></value>
+		public DataTable Table {get;}
+
+
+		/// <summary>
+		/// The previous selected column index.  May be invalid e.g. when the selection has been changed as a result of replacing the existing Table with a smaller one
+		/// </summary>
+		/// <value></value>
+		public int OldCol {get;}
+
+
+		/// <summary>
+		/// The newly selected column index.
+		/// </summary>
+		/// <value></value>
+		public int NewCol {get;}
+
+
+		/// <summary>
+		/// The previous selected row index.  May be invalid e.g. when the selection has been changed as a result of deleting rows from the table
+		/// </summary>
+		/// <value></value>
+		public int OldRow {get;}
+
+
+		/// <summary>
+		/// The newly selected row index.
+		/// </summary>
+		/// <value></value>
+		public int NewRow {get;}
+
+		/// <summary>
+		/// Creates a new instance of arguments describing a change in selected cell in a <see cref="TableView"/>
+		/// </summary>
+		/// <param name="t"></param>
+		/// <param name="oldCol"></param>
+		/// <param name="newCol"></param>
+		/// <param name="oldRow"></param>
+		/// <param name="newRow"></param>
+		public SelectedCellChangedEventArgs(DataTable t, int oldCol, int newCol, int oldRow, int newRow)
+		{
+			Table = t;
+			OldCol = oldCol;
+			NewCol = newCol;
+			OldRow = oldRow;
+			NewRow = newRow;
+		}
+	}
 }

UnitTests/TableViewTests.cs

@@ -67,6 +67,66 @@ namespace UnitTests {
             Assert.Equal(1,tableView.RowOffset);
             Assert.Equal(1,tableView.ColumnOffset);
         }
+
+        [Fact]
+        public void SelectedCellChanged_NotFiredForSameValue()
+        {
+            var tableView = new TableView(){
+                Table = BuildTable(25,50)
+            };
+
+            bool called = false;
+            tableView.SelectedCellChanged += (e)=>{called=true;};
+
+            Assert.Equal(0,tableView.SelectedColumn);
+            Assert.False(called);
+            
+            // Changing value to same as it already was should not raise an event
+            tableView.SelectedColumn = 0;
+
+            Assert.False(called);
+
+            tableView.SelectedColumn = 10;
+            Assert.True(called);
+        }
+
+
+
+        [Fact]
+        public void SelectedCellChanged_SelectedColumnIndexesCorrect()
+        {
+            var tableView = new TableView(){
+                Table = BuildTable(25,50)
+            };
+
+            bool called = false;
+            tableView.SelectedCellChanged += (e)=>{
+                called=true;
+                Assert.Equal(0,e.OldCol);
+                Assert.Equal(10,e.NewCol);
+            };
+            
+            tableView.SelectedColumn = 10;
+            Assert.True(called);
+        }
+
+        [Fact]
+        public void SelectedCellChanged_SelectedRowIndexesCorrect()
+        {
+            var tableView = new TableView(){
+                Table = BuildTable(25,50)
+            };
+
+            bool called = false;
+            tableView.SelectedCellChanged += (e)=>{
+                called=true;
+                Assert.Equal(0,e.OldRow);
+                Assert.Equal(10,e.NewRow);
+            };
+            
+            tableView.SelectedRow = 10;
+            Assert.True(called);
+        }
         
         /// <summary>
 		/// Builds a simple table of string columns with the requested number of columns and rows