AI: Add 2D translation gizmo for axis-constrained node moves

ZeroSpace/ZeroSpace.MapEditor/Views/MapDrawable.cs

@@ -4,6 +4,15 @@ using ZeroSpace.MapEditor.Services;
 
 namespace ZeroSpace.MapEditor.Views;
 
+/// <summary>Which part of the translation gizmo was hit or is active.</summary>
+public enum GizmoPart
+{
+    None,
+    Center,
+    XAxis,
+    YAxis,
+}
+
 /// <summary>
 /// Draws the star map: connection lines between connected systems and
 /// one circle per system. Names are intentionally not drawn on the
@@ -13,6 +22,9 @@ public sealed class MapDrawable : IDrawable
 {
     public const double NodeRadius = 14;
 
+    /// <summary>Screen-space length of each gizmo axis arm, in pixels.</summary>
+    public const double GizmoArmLength = 64;
+
     public IList<MapNode> Nodes { get; set; } = Array.Empty<MapNode>();
 
     public Func<string, MapNode?> FindNode { get; set; } = _ => null;
@@ -32,6 +44,12 @@ public sealed class MapDrawable : IDrawable
     /// <summary>Whether the galaxy map background is shown.</summary>
     public bool ShowBackground { get; set; } = true;
 
+    /// <summary>Node the translation gizmo is drawn for (the active selection).</summary>
+    public MapNode? GizmoNode { get; set; }
+
+    /// <summary>Gizmo part currently hovered or being dragged, for highlight.</summary>
+    public GizmoPart ActiveGizmoPart { get; set; } = GizmoPart.None;
+
     public void Draw(ICanvas canvas, RectF dirtyRect)
     {
         canvas.FillColor = Color.FromArgb("#1e2430");
@@ -92,6 +110,82 @@ public sealed class MapDrawable : IDrawable
             canvas.StrokeSize = 1.5f;
             canvas.DrawRectangle(box);
         }
+
+        if (GizmoNode is not null)
+        {
+            DrawGizmo(canvas, GizmoNode);
+        }
+    }
+
+    /// <summary>
+    /// Draws the 2D translation gizmo at the node's screen position:
+    /// a red +X arm, a green +Y arm, and a center square for free XY moves.
+    /// Screen-space, so it stays the same size at any zoom level.
+    /// </summary>
+    private void DrawGizmo(ICanvas canvas, MapNode node)
+    {
+        var cx = (float)(node.X * Scale + OffsetX);
+        var cy = (float)(node.Y * Scale + OffsetY);
+        const float arm = (float)GizmoArmLength;
+
+        DrawGizmoArm(canvas, cx, cy, cx + arm, cy, isX: true,
+            active: ActiveGizmoPart == GizmoPart.XAxis);
+        DrawGizmoArm(canvas, cx, cy, cx, cy + arm, isX: false,
+            active: ActiveGizmoPart == GizmoPart.YAxis);
+
+        // Center handle: free XY move.
+        const float size = 12f;
+        var centerColor = ActiveGizmoPart == GizmoPart.Center
+            ? Color.FromArgb("#fde047")
+            : Color.FromArgb("#eab308");
+        canvas.FillColor = Color.FromArgb("#111827");
+        canvas.FillRectangle(cx - size / 2 - 2, cy - size / 2 - 2, size + 4, size + 4);
+        canvas.FillColor = centerColor;
+        canvas.FillRectangle(cx - size / 2, cy - size / 2, size, size);
+    }
+
+    private static void DrawGizmoArm(ICanvas canvas, float x1, float y1, float x2, float y2,
+        bool isX, bool active)
+    {
+        var color = isX
+            ? (active ? Color.FromArgb("#f87171") : Color.FromArgb("#ef4444"))
+            : (active ? Color.FromArgb("#4ade80") : Color.FromArgb("#22c55e"));
+
+        // Dark underlay so the arm reads against the bright galaxy map.
+        canvas.StrokeColor = Color.FromArgb("#111827");
+        canvas.StrokeSize = 5;
+        canvas.DrawLine(x1, y1, x2, y2);
+        canvas.StrokeColor = color;
+        canvas.StrokeSize = 3;
+        canvas.DrawLine(x1, y1, x2, y2);
+
+        // Arrowhead pointing along the axis.
+        const float headLen = 12f;
+        const float headHalf = 6f;
+        PointF tip, a, b;
+        if (isX)
+        {
+            tip = new PointF(x2, y2);
+            a = new PointF(x2 - headLen, y2 - headHalf);
+            b = new PointF(x2 - headLen, y2 + headHalf);
+        }
+        else
+        {
+            tip = new PointF(x2, y2);
+            a = new PointF(x2 - headHalf, y2 - headLen);
+            b = new PointF(x2 + headHalf, y2 - headLen);
+        }
+
+        var head = new PathF();
+        head.MoveTo(tip);
+        head.LineTo(a);
+        head.LineTo(b);
+        head.Close();
+        canvas.FillColor = color;
+        canvas.FillPath(head);
+        canvas.StrokeColor = Color.FromArgb("#111827");
+        canvas.StrokeSize = 1.5f;
+        canvas.DrawPath(head);
     }
 
     /// <summary>