Recovering GrabbingMouse and UnGrabbingMouse implementation.

Terminal.Gui/Core/Application.cs

@@ -162,7 +162,7 @@ namespace Terminal.Gui {
 				if (alternateForwardKey != value) {
 					var oldKey = alternateForwardKey;
 					alternateForwardKey = value;
-					OnAlternateForwardKeyChanged (new KeyChangedEventArgs(oldKey,value));
+					OnAlternateForwardKeyChanged (new KeyChangedEventArgs (oldKey, value));
 				}
 			}
 		}
@@ -186,7 +186,7 @@ namespace Terminal.Gui {
 				if (alternateBackwardKey != value) {
 					var oldKey = alternateBackwardKey;
 					alternateBackwardKey = value;
-					OnAlternateBackwardKeyChanged (new KeyChangedEventArgs(oldKey,value));
+					OnAlternateBackwardKeyChanged (new KeyChangedEventArgs (oldKey, value));
 				}
 			}
 		}
@@ -210,7 +210,7 @@ namespace Terminal.Gui {
 				if (quitKey != value) {
 					var oldKey = quitKey;
 					quitKey = value;
-					OnQuitKeyChanged (new KeyChangedEventArgs(oldKey,value));
+					OnQuitKeyChanged (new KeyChangedEventArgs (oldKey, value));
 				}
 			}
 		}
@@ -720,6 +720,16 @@ namespace Terminal.Gui {
 		/// </summary>
 		public static View MouseGrabView => mouseGrabView;
 
+		/// <summary>
+		/// Event to be invoked when a view want grab the mouse which can be canceled.
+		/// </summary>
+		public static event EventHandler<GrabMouseEventArgs> GrabbingMouse;
+
+		/// <summary>
+		/// Event to be invoked when a view want ungrab the mouse which can be canceled.
+		/// </summary>
+		public static event EventHandler<GrabMouseEventArgs> UnGrabbingMouse;
+
 		/// <summary>
 		/// Event to be invoked when a view grab the mouse.
 		/// </summary>
@@ -739,9 +749,11 @@ namespace Terminal.Gui {
 		{
 			if (view == null)
 				return;
-			OnGrabbedMouse (view);
-			mouseGrabView = view;
-			Driver.UncookMouse ();
+			if (!OnGrabbingMouse (view)) {
+				OnGrabbedMouse (view);
+				mouseGrabView = view;
+				Driver.UncookMouse ();
+			}
 		}
 
 		/// <summary>
@@ -751,16 +763,36 @@ namespace Terminal.Gui {
 		{
 			if (mouseGrabView == null)
 				return;
-			OnUnGrabbedMouse (mouseGrabView);
-			mouseGrabView = null;
-			Driver.CookMouse ();
+			if (!OnUnGrabbingMouse (mouseGrabView)) {
+				OnUnGrabbedMouse (mouseGrabView);
+				mouseGrabView = null;
+				Driver.CookMouse ();
+			}
+		}
+
+		static bool OnGrabbingMouse (View view)
+		{
+			if (view == null)
+				return false;
+			var evArgs = new GrabMouseEventArgs (view);
+			GrabbingMouse?.Invoke (view, evArgs);
+			return evArgs.Cancel;
+		}
+
+		static bool OnUnGrabbingMouse (View view)
+		{
+			if (view == null)
+				return false;
+			var evArgs = new GrabMouseEventArgs (view);
+			UnGrabbingMouse?.Invoke (view, evArgs);
+			return evArgs.Cancel;
 		}
 
 		static void OnGrabbedMouse (View view)
 		{
 			if (view == null)
 				return;
-			GrabbedMouse?.Invoke (view, new ViewEventArgs(view));
+			GrabbedMouse?.Invoke (view, new ViewEventArgs (view));
 		}
 
 		static void OnUnGrabbedMouse (View view)
@@ -1029,7 +1061,7 @@ namespace Terminal.Gui {
 				Driver.Refresh ();
 			}
 
-			NotifyNewRunState?.Invoke (toplevel, new RunStateEventArgs(rs));
+			NotifyNewRunState?.Invoke (toplevel, new RunStateEventArgs (rs));
 			return rs;
 		}
 
@@ -1497,7 +1529,7 @@ namespace Terminal.Gui {
 		static void OnNotifyStopRunState (Toplevel top)
 		{
 			if (ExitRunLoopAfterFirstIteration) {
-				NotifyStopRunState?.Invoke (top, new ToplevelEventArgs(top));
+				NotifyStopRunState?.Invoke (top, new ToplevelEventArgs (top));
 			}
 		}
 
@@ -1516,7 +1548,7 @@ namespace Terminal.Gui {
 				t.SetRelativeLayout (full);
 				t.LayoutSubviews ();
 				t.PositionToplevels ();
-				t.OnResized (new SizeChangedEventArgs(full.Size));
+				t.OnResized (new SizeChangedEventArgs (full.Size));
 			}
 			Refresh ();
 		}

Terminal.Gui/Core/Toplevel.cs

@@ -120,7 +120,7 @@ namespace Terminal.Gui {
 
 		internal virtual void OnChildUnloaded (Toplevel top)
 		{
-			ChildUnloaded?.Invoke (this, new ToplevelEventArgs(top));
+			ChildUnloaded?.Invoke (this, new ToplevelEventArgs (top));
 		}
 
 		internal virtual void OnChildLoaded (Toplevel top)
@@ -159,7 +159,7 @@ namespace Terminal.Gui {
 
 		internal virtual void OnActivate (Toplevel deactivated)
 		{
-			Activate?.Invoke (this, new ToplevelEventArgs(deactivated));
+			Activate?.Invoke (this, new ToplevelEventArgs (deactivated));
 		}
 
 		/// <summary>
@@ -221,6 +221,9 @@ namespace Terminal.Gui {
 		{
 			ColorScheme = Colors.TopLevel;
 
+			Application.GrabbingMouse += Application_GrabbingMouse;
+			Application.UnGrabbingMouse += Application_UnGrabbingMouse;
+
 			// Things this view knows how to do
 			AddCommand (Command.QuitToplevel, () => { QuitToplevel (); return true; });
 			AddCommand (Command.Suspend, () => { Driver.Suspend (); ; return true; });
@@ -256,6 +259,20 @@ namespace Terminal.Gui {
 			AddKeyBinding (Key.L | Key.CtrlMask, Command.Refresh);
 		}
 
+		private void Application_UnGrabbingMouse (object sender, GrabMouseEventArgs e)
+		{
+			if (Application.MouseGrabView == this && dragPosition.HasValue) {
+				e.Cancel = true;
+			}
+		}
+
+		private void Application_GrabbingMouse (object sender, GrabMouseEventArgs e)
+		{
+			if (Application.MouseGrabView == this && dragPosition.HasValue) {
+				e.Cancel = true;
+			}
+		}
+
 		/// <summary>
 		/// Invoked when the <see cref="Application.AlternateForwardKey"/> is changed.
 		/// </summary>
@@ -824,8 +841,8 @@ namespace Terminal.Gui {
 			}
 
 			if (mouseEvent.Flags.HasFlag (MouseFlags.Button1Released) && dragPosition.HasValue) {
-				Application.UngrabMouse ();
 				dragPosition = null;
+				Application.UngrabMouse ();
 			}
 
 			//System.Diagnostics.Debug.WriteLine ($"dragPosition after: {dragPosition.HasValue}");