feat(cutoff): tell users Space turns the manual cut-off line

Issue #13 asked whether a Sheet Cut-Off can be rotated; Space already
toggles vertical/horizontal, but nothing said so. The tool now shows a
"Space: turn horizontal" tag by the pointer, spells out its keys in the
status bar, and F1 opens a new sheet-cutoff help topic while it is
active (actions can now supply a status hint and a help topic).

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

OpenNest.WinForms.Tests/Actions/ActionCutOffHintTests.cs

@@ -0,0 +1,33 @@
+using System.Reflection;
+using System.Windows.Forms;
+using OpenNest.Actions;
+using OpenNest.Controls;
+using OpenNest.Help;
+
+namespace OpenNest.WinForms.Tests.Actions;
+
+/// <summary>The manual cut-off tool says how to turn its line and where its help is.</summary>
+public class ActionCutOffHintTests
+{
+    private static void PressKey(PlateView view, Keys key) =>
+        typeof(Control).GetMethod("OnKeyDown", BindingFlags.Instance | BindingFlags.NonPublic)!
+            .Invoke(view, new object[] { new KeyEventArgs(key) });
+
+    [Fact]
+    public void StatusNamesTheAxisAndSpaceTurnsIt() => StaTestThread.Run(() =>
+    {
+        using var view = new PlateView { Plate = new Plate(48, 120) };
+
+        view.SetAction(typeof(ActionCutOff));
+        Assert.Equal(
+            "Sheet Cut-Off: click to add a vertical line, Space turns it horizontal, Esc finishes, F1 for help",
+            view.Status);
+        Assert.Equal(HelpTopics.SheetCutOff, view.ActionHelpTopic);
+
+        PressKey(view, Keys.Space);
+        Assert.StartsWith("Sheet Cut-Off: click to add a horizontal line, Space turns it vertical", view.Status);
+
+        view.SetAction(typeof(ActionSelect));
+        Assert.Null(view.ActionHelpTopic);
+    }, TimeSpan.FromMinutes(1), "The STA test did not complete.");
+}

OpenNest/Actions/Action.cs

@@ -33,6 +33,12 @@ namespace OpenNest.Actions
         /// </summary>
         public virtual bool ResumeOnEscape => true;
 
+        /// <summary>Status bar guidance shown after the action's name, or null for the name alone.</summary>
+        public virtual string Hint => null;
+
+        /// <summary>The help topic F1 opens while this action is active, or null for the general help.</summary>
+        public virtual string HelpTopic => null;
+
         public virtual void OnPlateChanged() { }
 
         public virtual void ConnectEvents() { }

OpenNest/Actions/ActionCutOff.cs

@@ -6,6 +6,7 @@ using System.Windows.Forms;
 using OpenNest.CNC;
 using OpenNest.Controls;
 using OpenNest.Geometry;
+using OpenNest.Help;
 
 namespace OpenNest.Actions
 {
@@ -50,6 +51,17 @@ namespace OpenNest.Actions
 
         public override bool IsBusy() => false;
 
+        public override string Hint =>
+            $"click to add a {AxisName(lockedAxis)} line, Space turns it {AxisName(OtherAxis(lockedAxis))}, Esc finishes, F1 for help";
+
+        public override string HelpTopic => HelpTopics.SheetCutOff;
+
+        private static CutOffAxis OtherAxis(CutOffAxis axis) =>
+            axis == CutOffAxis.Vertical ? CutOffAxis.Horizontal : CutOffAxis.Vertical;
+
+        private static string AxisName(CutOffAxis axis) =>
+            axis == CutOffAxis.Vertical ? "vertical" : "horizontal";
+
         private void OnMouseMove(object sender, MouseEventArgs e)
         {
             var pt = plateView.CurrentPoint;
@@ -78,8 +90,8 @@ namespace OpenNest.Actions
         {
             if (e.KeyCode == Keys.Space)
             {
-                lockedAxis =
-                    lockedAxis == CutOffAxis.Vertical ? CutOffAxis.Horizontal : CutOffAxis.Vertical;
+                lockedAxis = OtherAxis(lockedAxis);
+                plateView.RefreshActionStatus();
 
                 if (previewCutOff != null)
                 {
@@ -126,6 +138,22 @@ namespace OpenNest.Actions
                     e.Graphics.DrawLine(pen, pt1, pt2);
                 }
             }
+
+            DrawRotateTag(e.Graphics);
+        }
+
+        // The status bar is easy to miss, so the cursor says how to turn the line.
+        private void DrawRotateTag(Graphics g)
+        {
+            var text = $"Space: turn {AxisName(OtherAxis(lockedAxis))}";
+            var cursor = plateView.PointWorldToGraph(plateView.CurrentPoint);
+            var size = g.MeasureString(text, plateView.Font);
+            var rect = new RectangleF(cursor.X + 16f, cursor.Y + 16f, size.Width + 6, size.Height + 4);
+
+            using (var background = new SolidBrush(Color.FromArgb(230, Color.White)))
+                g.FillRectangle(background, rect);
+            g.DrawRectangle(Pens.DimGray, rect.X, rect.Y, rect.Width, rect.Height);
+            g.DrawString(text, plateView.Font, Brushes.Black, rect.X + 3, rect.Y + 2);
         }
     }
 }

OpenNest/Controls/ActionManager.cs

@@ -40,7 +40,7 @@ namespace OpenNest.Controls
             }
 
             currentAction = action;
-            view.Status = GetDisplayName(type);
+            RefreshStatus();
         }
 
         public void SetAction(Type type, params object[] args)
@@ -63,7 +63,7 @@ namespace OpenNest.Controls
                 return;
 
             currentAction = action;
-            view.Status = GetDisplayName(type);
+            RefreshStatus();
         }
 
         public void ProcessEscapeKey()
@@ -98,7 +98,7 @@ namespace OpenNest.Controls
             action.ConnectEvents();
             currentAction = action;
 
-            view.Status = GetDisplayName(action.GetType());
+            RefreshStatus();
         }
 
         public void OnPlateChanged()
@@ -119,6 +119,14 @@ namespace OpenNest.Controls
             }
         }
 
+        /// <summary>Shows the current action's name and hint in the status bar.</summary>
+        public void RefreshStatus()
+        {
+            var name = GetDisplayName(currentAction.GetType());
+            var hint = currentAction.Hint;
+            view.Status = string.IsNullOrEmpty(hint) ? name : $"{name}: {hint}";
+        }
+
         private string GetDisplayName(Type type)
         {
             var attributes = type.GetCustomAttributes(true);

OpenNest/Controls/PlateView.cs

@@ -866,6 +866,12 @@ namespace OpenNest.Controls
         public void SetAction(Type type, params object[] args) =>
             actionManager.SetAction(type, args);
 
+        /// <summary>Shows the current action's name and hint again after the hint changed.</summary>
+        public void RefreshActionStatus() => actionManager.RefreshStatus();
+
+        /// <summary>The help topic for the current action, or null when it has none.</summary>
+        public string ActionHelpTopic => actionManager.CurrentAction?.HelpTopic;
+
         public void AlignSelected(AlignType alignType) => selection.AlignSelected(alignType);
 
         public void AlignSelected(AlignType alignType, LayoutPart fixedPart) =>

OpenNest/Forms/MainForm.cs

@@ -99,6 +99,12 @@ namespace OpenNest.Forms
             }
             if (ProcessUndoKeys(keyData))
                 return true;
+            // F1 opens the active tool's topic before the Help menu's general help.
+            if (keyData == Keys.F1 && activeForm?.PlateView?.ActionHelpTopic is { } topic)
+            {
+                HelpTopics.Show(this, topic);
+                return true;
+            }
 
             return base.ProcessCmdKey(ref msg, keyData);
         }

OpenNest/Help/HelpTopics.cs

@@ -19,6 +19,7 @@ namespace OpenNest.Help
         public const string AutoNest = "auto-nest";
         public const string Post = "post";
         public const string SupportGrid = "support-grid";
+        public const string SheetCutOff = "sheet-cutoff";
 
         /// <summary>Overrides the help folder, e.g. a local opennest-help <c>site/</c> build.</summary>
         public const string DirectoryVariable = "OPENNEST_HELP_DIR";