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

Terminal.Gui/Application.cs

@@ -147,6 +147,9 @@ internal static void ResetState ()
 
         // Mouse
         _mouseEnteredView = null;
+        _lastViewButtonPressed = null;
+        _canProcessClickedEvent = true;
+        _isMouseDown = false;
         WantContinuousButtonPressedView = null;
         MouseEvent = null;
         GrabbedMouse = null;
@@ -1550,6 +1553,9 @@ private static void OnUnGrabbedMouse (View view)
 
     // 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>
@@ -1578,6 +1584,38 @@ internal static void OnMouseEvent (MouseEvent mouseEvent)
             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)
@@ -1597,7 +1635,8 @@ internal static void OnMouseEvent (MouseEvent mouseEvent)
                 Y = frameLoc.Y,
                 Flags = mouseEvent.Flags,
                 ScreenPosition = new (mouseEvent.X, mouseEvent.Y),
-                View = MouseGrabView
+                View = view ?? MouseGrabView,
+                IsMouseDown = _isMouseDown
             };
 
             if ((MouseGrabView.Viewport with { Location = Point.Empty }).Contains (viewRelativeMouseEvent.X, viewRelativeMouseEvent.Y) is false)
@@ -1606,8 +1645,8 @@ internal static void OnMouseEvent (MouseEvent mouseEvent)
                 _mouseEnteredView?.NewMouseLeaveEvent (mouseEvent);
             }
 
-            //System.Diagnostics.Debug.WriteLine ($"{nme.Flags};{nme.X};{nme.Y};{mouseGrabView}");
-            if (MouseGrabView?.NewMouseEvent (viewRelativeMouseEvent) == true)
+            if ((MouseGrabView?.WantMousePositionReports == true || MouseGrabView?.WantContinuousButtonPressed == true)
+                && MouseGrabView?.NewMouseEvent (viewRelativeMouseEvent) == true)
             {
                 return;
             }
@@ -1622,7 +1661,6 @@ internal static void OnMouseEvent (MouseEvent mouseEvent)
             WantContinuousButtonPressedView = null;
         }
 
-
         if (view is not Adornment)
         {
             if ((view is null || view == OverlappedTop)
@@ -1660,7 +1698,8 @@ internal static void OnMouseEvent (MouseEvent mouseEvent)
                 Y = frameLoc.Y,
                 Flags = mouseEvent.Flags,
                 ScreenPosition = new (mouseEvent.X, mouseEvent.Y),
-                View = view
+                View = view,
+                IsMouseDown = _isMouseDown
             };
         }
         else if (view.ViewportToScreen (Rectangle.Empty with { Size = view.Viewport.Size }).Contains (mouseEvent.X, mouseEvent.Y))
@@ -1673,7 +1712,8 @@ internal static void OnMouseEvent (MouseEvent mouseEvent)
                 Y = viewportLocation.Y,
                 Flags = mouseEvent.Flags,
                 ScreenPosition = new (mouseEvent.X, mouseEvent.Y),
-                View = view
+                View = view,
+                IsMouseDown = _isMouseDown
             };
         }
 
@@ -1738,6 +1778,7 @@ internal static void OnMouseEvent (MouseEvent mouseEvent)
 
         BringOverlappedTopToFront ();
     }
+
 #nullable restore
 
     #endregion Mouse handling

Terminal.Gui/Input/Mouse.cs

@@ -143,6 +143,11 @@ public class MouseEvent
     /// </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}"; }

Terminal.Gui/View/Adornment/Border.cs

@@ -59,6 +59,7 @@ public Border (View parent) : base (parent)
 
         HighlightStyle |= HighlightStyle.Pressed;
         Highlight += Border_Highlight;
+        WantMousePositionReports = true;
     }
 
 #if SUBVIEW_BASED_BORDER