Fixes #3312. Mouse API makes it way too hard to track button pressed.

Terminal.Gui/Application.cs

@@ -143,6 +143,9 @@
 
         // Mouse
         _mouseEnteredView = null;
+        _lastViewButtonPressed = null;
+        _canProcessClickedEvent = true;
+        _isMouseDown = false;
         WantContinuousButtonPressedView = null;
         MouseEvent = null;
         GrabbedMouse = null;
@@ -1432,6 +1435,9 @@
 
     // Used by OnMouseEvent to track the last view that was clicked on.
     internal static View? _mouseEnteredView;
+    internal static View? _lastViewButtonPressed;
+    internal static bool _canProcessClickedEvent = true;
+    internal static bool? _isMouseDown;
 
     /// <summary>Event fired when a mouse move or click occurs. Coordinates are screen relative.</summary>
     /// <remarks>
@@ -1441,12 +1447,12 @@
     ///     </para>
     ///     <para>The <see cref="MouseEvent.View"/> will contain the <see cref="View"/> that contains the mouse coordinates.</para>
     /// </remarks>
     public static event EventHandler<MouseEvent> MouseEvent;
 
     /// <summary>Called when a mouse event occurs. Raises the <see cref="MouseEvent"/> event.</summary>
     /// <remarks>This method can be used to simulate a mouse event, e.g. in unit tests.</remarks>
     /// <param name="a">The mouse event with coordinates relative to the screen.</param>
     internal static void OnMouseEvent (MouseEvent mouseEvent)
     {
         if (IsMouseDisabled)
         {
@@ -1461,6 +1467,38 @@
             mouseEvent.View = view;
         }
 
+        if (_lastViewButtonPressed is null && mouseEvent.Flags is MouseFlags.Button1Pressed or MouseFlags.Button2Pressed or MouseFlags.Button3Pressed or MouseFlags.Button4Pressed)
+        {
+            _lastViewButtonPressed = view;
+            _isMouseDown = true;
+        }
+        else if (_lastViewButtonPressed is { } && mouseEvent.Flags is MouseFlags.Button1Released or MouseFlags.Button2Released or MouseFlags.Button3Released or MouseFlags.Button4Released)
+        {
+            if (_lastViewButtonPressed != view)
+            {
+                _canProcessClickedEvent = false;
+            }
+
+            _lastViewButtonPressed = null;
+            _isMouseDown = false;
+        }
+        else if (!_canProcessClickedEvent && mouseEvent.Flags is MouseFlags.Button1Clicked or MouseFlags.Button2Clicked or MouseFlags.Button3Clicked or MouseFlags.Button4Clicked)
+        {
+            _canProcessClickedEvent = true;
+            _isMouseDown = null;
+
+            return;
+        }
+        else if (!mouseEvent.Flags.HasFlag(MouseFlags.ReportMousePosition))
+        {
+            _lastViewButtonPressed = null;
+            _isMouseDown = null;
+        }
+        else
+        {
+            _isMouseDown = null;
+        }
+
         MouseEvent?.Invoke (null, mouseEvent);
 
         if (mouseEvent.Handled)
@@ -1480,13 +1518,18 @@
                 Y = boundsLoc.Y,
                 Flags = mouseEvent.Flags,
                 ScreenPosition = new (mouseEvent.X, mouseEvent.Y),
-                View = MouseGrabView
+                View = view ?? MouseGrabView,
+                IsMouseDown = _isMouseDown
             };
 
             if (MouseGrabView.Bounds.Contains (viewRelativeMouseEvent.X, viewRelativeMouseEvent.Y) is false)
             {
                 // The mouse has moved outside the bounds of the view that grabbed the mouse
-                _mouseEnteredView?.NewMouseLeaveEvent (mouseEvent);
+                // Give a chance for the current view process the event
+                if (ProcessMouseEvent (mouseEvent, view))
+                {
+                    return;
+                }
             }
 
             //System.Diagnostics.Debug.WriteLine ($"{nme.Flags};{nme.X};{nme.Y};{mouseGrabView}");
@@ -1496,6 +1539,11 @@
             }
         }
 
+        ProcessMouseEvent (mouseEvent, view);
+    }
+
+    private static bool ProcessMouseEvent (MouseEvent mouseEvent, View? view)
+    {
         if (view is { WantContinuousButtonPressed: true })
         {
             WantContinuousButtonPressedView = view;
@@ -1521,14 +1569,14 @@
 
                 if (view is { } && view != OverlappedTop && top != Current)
                 {
                     MoveCurrent ((Toplevel)top);
                 }
             }
         }
 
         if (view is null)
         {
-            return;
+            return false;
         }
 
         MouseEvent? me = null;
@@ -1543,7 +1591,8 @@
                 Y = frameLoc.Y,
                 Flags = mouseEvent.Flags,
                 ScreenPosition = new (mouseEvent.X, mouseEvent.Y),
-                View = view
+                View = view,
+                IsMouseDown = _isMouseDown
             };
         }
         else if (view.BoundsToScreen (view.Bounds).Contains (mouseEvent.X, mouseEvent.Y))
@@ -1556,13 +1605,14 @@
                 Y = boundsPoint.Y,
                 Flags = mouseEvent.Flags,
                 ScreenPosition = new (mouseEvent.X, mouseEvent.Y),
-                View = view
+                View = view,
+                IsMouseDown = _isMouseDown
             };
         }
 
         if (me is null)
         {
-            return;
+            return false;
         }
 
         if (_mouseEnteredView is null)
@@ -1579,7 +1629,7 @@
 
         if (!view.WantMousePositionReports && mouseEvent.Flags == MouseFlags.ReportMousePosition)
         {
-            return;
+            return false;
         }
 
         WantContinuousButtonPressedView = view.WantContinuousButtonPressed ? view : null;
@@ -1589,10 +1639,12 @@
         if (view.NewMouseEvent (me) == false)
         {
             // Should we bubble up the event, if it is not handled?
-            //return;
+            return false;
         }
 
         BringOverlappedTopToFront ();
+
+        return true;
     }
 #nullable restore
 

Terminal.Gui/Input/Mouse.cs

@@ -138,11 +138,16 @@
     ///         mouse has moved.
     ///     </para>
     ///     <para>
     ///         Calculated and processed in <see cref="Application.OnMouseEvent(MouseEventEventArgs)"/>.
     ///     </para>
     /// </remarks>
     public Point ScreenPosition { get; set; }
 
+    /// <summary>
+    ///     Indicates if the current mouse event has first pressed <see langword="true"/>, latest released <see langword="false"/> or none <see langword="null"/>.
+    /// </summary>
+    public bool? IsMouseDown { get; set; }
+
     /// <summary>Returns a <see cref="T:System.String"/> that represents the current <see cref="MouseEvent"/>.</summary>
     /// <returns>A <see cref="T:System.String"/> that represents the current <see cref="MouseEvent"/>.</returns>
     public override string ToString () { return $"({X},{Y}):{Flags}"; }