Fixes tui-cs#5143. ColorBar mouse updates use MouseBindings with grab/ungrab (tui-cs#5289)

Move value-update logic from OnMouseEvent into a Command.Activate
handler bound via MouseBindings.Add. This makes mouse interaction
cancellable by external code (e.g. TerminalGuiDesigner) which can
clear the bindings.

Add GrabMouse/UngrabMouse in OnMouseEvent so drag events are routed
exclusively to the originating bar, preventing cross-bar drag
contamination.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: YourRobotOverlord

Terminal.Gui/Views/Color/ColorBar.cs

@@ -26,13 +26,47 @@ protected ColorBar ()
         AddCommand (Command.LeftStart, _ => SetZero ());
         AddCommand (Command.RightEnd, _ => SetMax ());
 
+        // Override Activate to handle mouse-press and drag. When triggered by a left-button press
+        // (initial click or drag), extract the position from the MouseBinding context, update
+        // Value, set focus, and grab the mouse so subsequent drag events are routed to this bar
+        // exclusively. Grabbing here (rather than in OnMouseEvent) ensures that if a consumer
+        // cancels the event by setting e.Handled=true in MouseEvent, the press command is never
+        // reached and no grab occurs.
+        AddCommand (
+                    Command.Activate,
+                    ctx =>
+                    {
+                        if (ctx?.Binding is MouseBinding { MouseEvent: { } mouse }
+                            && mouse.Flags.FastHasFlags (MouseFlags.LeftButtonPressed))
+                        {
+                            UpdateValueFromMousePosition (mouse);
+                            SetFocus ();
+                            App?.Mouse.GrabMouse (this);
+
+                            return true;
+                        }
+
+                        return DefaultActivateHandler (ctx);
+                    });
+
         KeyBindings.Add (Key.CursorLeft, Command.Left);
         KeyBindings.Add (Key.CursorRight, Command.Right);
         KeyBindings.Add (Key.CursorLeft.WithShift, Command.LeftExtend);
         KeyBindings.Add (Key.CursorRight.WithShift, Command.RightExtend);
         KeyBindings.Add (Key.Home, Command.LeftStart);
         KeyBindings.Add (Key.End, Command.RightEnd);
         MouseBindings.Remove (MouseFlags.LeftButtonClicked);
+
+        // Remove the base LeftButtonReleased → Activate binding so that releasing the mouse
+        // does not fire DefaultActivateHandler (Activating/Activated). UngrabMouse is still
+        // called from OnMouseEvent on release, so the grab lifecycle is unaffected.
+        MouseBindings.Remove (MouseFlags.LeftButtonReleased);
+
+        // Bind press and drag to Activate so external code can fully suppress mouse interaction
+        // by removing these two bindings (e.g. TerminalGuiDesigner editor mode). When both are
+        // absent no value update, focus change, grab, or drag routing occurs.
+        MouseBindings.Add (MouseFlags.LeftButtonPressed, Command.Activate);
+        MouseBindings.Add (MouseFlags.LeftButtonPressed | MouseFlags.PositionReport, Command.Activate);
     }
 
     /// <summary>
@@ -123,19 +157,24 @@ protected override bool OnDrawingContent (DrawContext? context)
     /// <inheritdoc/>
     protected override bool OnMouseEvent (Mouse mouse)
     {
-        if (mouse.Flags.FastHasFlags (MouseFlags.LeftButtonPressed))
+        // Release the grab on button-up so drag events stop routing exclusively to this bar.
+        // The grab itself is established in the Command.Activate handler so that cancelling the
+        // MouseEvent (e.Handled = true) prevents both the value update and the grab.
+        if (mouse.IsReleased && App?.Mouse.IsGrabbed (this) == true)
         {
-            if (mouse.Position!.Value.X >= _barStartsAt)
-            {
-                double v = MaxValue * ((double)mouse.Position!.Value.X - _barStartsAt) / (_barWidth - 1);
-                Value = Math.Clamp ((int)v, 0, MaxValue);
-            }
-            SetFocus ();
-
-            // Do not mark as handled to allow Activating to be raised
+            App.Mouse.UngrabMouse ();
         }
 
-        return mouse.Handled;
+        return false;
+    }
+
+    private void UpdateValueFromMousePosition (Mouse mouse)
+    {
+        if (mouse.Position is { } pos && pos.X >= _barStartsAt)
+        {
+            double v = MaxValue * ((double)pos.X - _barStartsAt) / (_barWidth - 1);
+            Value = Math.Clamp ((int)v, 0, MaxValue);
+        }
     }
 
     /// <summary>

Tests/UnitTestsParallelizable/Views/ColorPickerTests.cs

@@ -182,7 +182,7 @@ public void ClickingAtEndOfBar_SetsMaxValue ()
         cp.Draw (); // Draw is needed to update TrianglePosition
 
         // Click at the end of the Red bar
-        cp.Focused!.RaiseMouseEvent (new Mouse
+        cp.Focused!.NewMouseEvent (new Mouse
         {
             Flags = MouseFlags.LeftButtonPressed, Position = new Point (19, 0) // Assuming 0-based indexing
         });
@@ -213,7 +213,7 @@ public void ClickingBeyondBar_ChangesToMaxValue ()
         cp.Draw (); // Draw is needed to update TrianglePosition
 
         // Click beyond the bar
-        cp.Focused!.RaiseMouseEvent (new Mouse
+        cp.Focused!.NewMouseEvent (new Mouse
         {
             Flags = MouseFlags.LeftButtonPressed, Position = new Point (21, 0) // Beyond the bar
         });
@@ -243,33 +243,17 @@ public void ClickingDifferentBars_ChangesFocus ()
 
         cp.Draw (); // Draw is needed to update TrianglePosition
 
-        // Click on Green bar
+        // Click on Green bar (press then release to complete the click cycle and release grab)
         cp.App!.Mouse.RaiseMouseEvent (new Mouse { Flags = MouseFlags.LeftButtonPressed, ScreenPosition = new Point (0, 1) });
-
-        //cp.SubViews.OfType<GBar> ()
-        //  .Single ()
-        //  .OnMouseEvent (
-        //                 new ()
-        //                 {
-        //                     Flags = MouseFlags.LeftButtonPressed,
-        //                     Position = new (0, 1)
-        //                 });
+        cp.App!.Mouse.RaiseMouseEvent (new Mouse { Flags = MouseFlags.LeftButtonReleased, ScreenPosition = new Point (0, 1) });
 
         cp.Draw (); // Draw is needed to update TrianglePosition
 
         Assert.IsAssignableFrom<GBar> (cp.Focused);
 
-        // Click on Blue bar
+        // Click on Blue bar (press then release to complete the click cycle and release grab)
         cp.App!.Mouse.RaiseMouseEvent (new Mouse { Flags = MouseFlags.LeftButtonPressed, ScreenPosition = new Point (0, 2) });
-
-        //cp.SubViews.OfType<BBar> ()
-        //  .Single ()
-        //  .OnMouseEvent (
-        //                 new ()
-        //                 {
-        //                     Flags = MouseFlags.LeftButtonPressed,
-        //                     Position = new (0, 2)
-        //                 });
+        cp.App!.Mouse.RaiseMouseEvent (new Mouse { Flags = MouseFlags.LeftButtonReleased, ScreenPosition = new Point (0, 2) });
 
         cp.Draw (); // Draw is needed to update TrianglePosition
 
@@ -706,14 +690,14 @@ public void RGB_MouseNavigation ()
 
         Assert.IsAssignableFrom<IColorBar> (cp.Focused);
 
-        cp.Focused!.RaiseMouseEvent (new Mouse { Flags = MouseFlags.LeftButtonPressed, Position = new Point (3, 0) });
+        cp.Focused!.NewMouseEvent (new Mouse { Flags = MouseFlags.LeftButtonPressed, Position = new Point (3, 0) });
 
         cp.Draw (); // Draw is needed to update TrianglePosition
 
         Assert.Equal (3, r.TrianglePosition);
         Assert.Equal ("#0F0000", hex.Text);
 
-        cp.Focused.RaiseMouseEvent (new Mouse { Flags = MouseFlags.LeftButtonPressed, Position = new Point (4, 0) });
+        cp.Focused.NewMouseEvent (new Mouse { Flags = MouseFlags.LeftButtonPressed, Position = new Point (4, 0) });
 
         cp.Draw (); // Draw is needed to update TrianglePosition
 
@@ -1100,4 +1084,81 @@ public void ValueChanging_ReceivesOldAndNewValues ()
     }
 
     #endregion
+
+    #region ColorBar Mouse Binding Tests (issue #5143)
+
+    // Copilot
+
+    [Fact]
+    public void ColorBar_MousePress_UpdatesValue ()
+    {
+        // Regression: pressing on a bar must still update its value after the
+        // value-update logic was moved from OnMouseEvent to Command.Activate.
+        ColorPicker cp = GetColorPicker (ColorModel.RGB, false);
+        cp.Draw ();
+
+        ColorBar r = GetColorBar (cp, ColorPickerPart.Bar1);
+        Assert.Equal (0, r.Value);
+
+        // Position 10 is inside the bar (bar starts at X=2 for "R:" label, width 18).
+        r.NewMouseEvent (new Mouse { Flags = MouseFlags.LeftButtonPressed, Position = new Point (10, 0) });
+
+        Assert.True (r.Value > 0, "Value must increase when pressing inside the bar.");
+
+        cp.App?.Dispose ();
+    }
+
+    [Fact]
+    public void ColorBar_MouseEvent_CanBeCancelled ()
+    {
+        // Subscribing to MouseEvent and setting Handled=true must prevent the value
+        // update. Previously the update happened in OnMouseEvent before the event was
+        // raised, making cancellation impossible.
+        ColorPicker cp = GetColorPicker (ColorModel.RGB, false);
+        cp.Draw ();
+
+        ColorBar r = GetColorBar (cp, ColorPickerPart.Bar1);
+        Assert.Equal (0, r.Value);
+
+        r.MouseEvent += (_, e) => { e.Handled = true; };
+
+        r.NewMouseEvent (new Mouse { Flags = MouseFlags.LeftButtonPressed, Position = new Point (10, 0) });
+
+        Assert.Equal (0, r.Value);
+
+        cp.App?.Dispose ();
+    }
+
+    [Fact]
+    public void ColorBar_Drag_BoundedToOriginatingBar ()
+    {
+        // Dragging the mouse from one bar into another bar must not alter the second
+        // bar's value. GrabMouse in Command.Activate (not OnMouseEvent) ensures all subsequent
+        // drag events are routed to the bar where the press originated.
+        ColorPicker cp = GetColorPicker (ColorModel.RGB, false);
+        cp.Draw ();
+
+        ColorBar g = GetColorBar (cp, ColorPickerPart.Bar2);
+        Assert.Equal (0, g.Value);
+
+        // Press on the Red bar row (Y=0 in screen coords).
+        cp.App!.Mouse.RaiseMouseEvent (new Mouse
+        {
+            Flags = MouseFlags.LeftButtonPressed,
+            ScreenPosition = new Point (10, 0)
+        });
+
+        // Drag into the Green bar row (Y=1) – grab in Command.Activate must route events to Red bar only.
+        cp.App!.Mouse.RaiseMouseEvent (new Mouse
+        {
+            Flags = MouseFlags.LeftButtonPressed | MouseFlags.PositionReport,
+            ScreenPosition = new Point (10, 1)
+        });
+
+        Assert.Equal (0, g.Value);
+
+        cp.App?.Dispose ();
+    }
+
+    #endregion
 }