Improve paper stamping experience (#17135)

Content.Client/Paper/UI/StampCollection.xaml.cs

@@ -0,0 +1,98 @@
+using System.Numerics;
+using Robust.Client.AutoGenerated;
+using Robust.Client.UserInterface.Controls;
+using Robust.Client.UserInterface.XAML;
+using Robust.Shared.Random;
+
+namespace Content.Client.Paper.UI;
+
+[GenerateTypedNameReferences]
+public sealed partial class StampCollection : Container
+{
+    private List<StampWidget> _stamps = new();
+
+    /// Seed for random number generator to place stamps deterministically
+    public int PlacementSeed;
+
+    public StampCollection()
+    {
+        RobustXamlLoader.Load(this);
+    }
+
+    /// <summary>
+    /// Remove any stamps from the page
+    /// </summary>
+    public void RemoveStamps()
+    {
+        _stamps.Clear();
+        InvalidateArrange();
+    }
+
+    /// <summary>
+    /// Adds a stamp to the display; will perform
+    /// automatic layout.
+    /// </summary>
+    public void AddStamp(StampWidget s)
+    {
+        _stamps.Add(s);
+        AddChild(s);
+    }
+
+    protected override Vector2 ArrangeOverride(Vector2 finalSize)
+    {
+        var random = new Random(PlacementSeed);
+        var r = (finalSize * 0.5f).Length();
+        var dtheta = -MathHelper.DegreesToRadians(90);
+        var theta0 = random.Next(0, 3) * dtheta;
+        var thisCenter = PixelSizeBox.TopLeft + finalSize * UIScale * 0.5f;
+
+        // Here's where we lay out the stamps. The first stamp goes in the
+        // center of this container; subsequent stamps will chose an angle
+        // (theta) to place the center of the stamp. The stamp is moved out
+        // as far as it can in that direction, taking the size and
+        // orientation of the stamp into account.
+        for (var i = 0; i < _stamps.Count; i++)
+        {
+            var stampOrientation = MathHelper.DegreesToRadians((random.NextFloat() - 0.5f) * 10.0f) ;
+            _stamps[i].Orientation = stampOrientation;
+
+            var theta = theta0 + dtheta * 0.5f + dtheta * i + (i > 4 ? MathF.Log(1 + i / 4) * dtheta : 0); // There is probably a better way to lay these out, to minimize overlaps
+            var childCenterOnCircle = thisCenter;
+            if (i > 0)
+            {
+                // First stamp can go in the center. Subsequent stamps have to find space.
+                childCenterOnCircle += new Vector2(MathF.Cos(theta), MathF.Sin(theta)) * r * UIScale;
+            }
+
+            var childHeLocal = _stamps[i].DesiredPixelSize * 0.5f;
+            var c = childHeLocal * MathF.Abs(MathF.Cos(stampOrientation));
+            var s = childHeLocal * MathF.Abs(MathF.Sin(stampOrientation));
+            var childHePage = new Vector2(c.X + s.Y, s.X + c.Y);
+            var controlBox = new UIBox2(PixelSizeBox.TopLeft, PixelSizeBox.TopLeft + finalSize * UIScale);
+            var clampedCenter = Clamp(Shrink(controlBox, childHePage), childCenterOnCircle);
+            var finalPosition = clampedCenter - childHePage;
+            var finalPositionAsInt = new Vector2i((int)finalPosition.X, (int)finalPosition.Y);
+            _stamps[i].ArrangePixel(new UIBox2i(finalPositionAsInt, finalPositionAsInt + _stamps[i].DesiredPixelSize));
+        }
+
+        return finalSize;
+    }
+
+    /// <summary>
+    /// Shrink a UIBox2 by a half extents, moving both the top-left and
+    /// bottom-right closer together.
+    /// </summary>
+    private UIBox2 Shrink(UIBox2 box, Vector2 shrinkHe)
+    {
+        return new UIBox2(box.TopLeft + shrinkHe, box.BottomRight - shrinkHe);
+    }
+
+    /// <summary>
+    /// Returns the input vector clamped to be within the UIBox
+    /// </summary>
+    private Vector2 Clamp(UIBox2 box, Vector2 point)
+    {
+        return Vector2.Min(box.BottomRight, Vector2.Max(box.TopLeft, point));
+    }
+}
+