Improve paper stamping experience (#17135)

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

@@ -0,0 +1,56 @@
+using System.Numerics;
+using Robust.Client.AutoGenerated;
+using Robust.Client.Graphics;
+using Robust.Client.UserInterface.Controls;
+using Robust.Client.UserInterface.XAML;
+using Robust.Shared.Prototypes;
+
+namespace Content.Client.Paper.UI;
+
+[GenerateTypedNameReferences]
+public sealed partial class StampLabel : Label
+{
+    /// A scale that's applied to the text to ensure it
+    /// fits in the allowed space.
+    private Vector2 _textScaling = Vector2.One;
+
+    /// Shader used to draw the stamps
+    private ShaderInstance? _stampShader;
+
+    /// Allows an additional orientation to be applied to
+    /// this control.
+    public float Orientation = 0.0f;
+
+    public StampLabel()
+    {
+        RobustXamlLoader.Load(this);
+
+        var prototypes = IoCManager.Resolve<IPrototypeManager>();
+        _stampShader = prototypes.Index<ShaderPrototype>("PaperStamp").InstanceUnique();
+    }
+
+    protected override Vector2 MeasureOverride(Vector2 availableSize)
+    {
+        var desiredTextSize = base.MeasureOverride(availableSize);
+        var clampedScale = Vector2.Min(availableSize / desiredTextSize, Vector2.One);
+        var keepAspectRatio = MathF.Min(clampedScale.X, clampedScale.Y);
+        const float shimmerReduction = 0.1f;
+        _textScaling = Vector2.One * MathF.Round(keepAspectRatio / shimmerReduction) * shimmerReduction;
+        return desiredTextSize;
+    }
+
+    protected override void Draw(DrawingHandleScreen handle)
+    {
+        var offset = new Vector2(PixelPosition.X * MathF.Cos(Orientation) - PixelPosition.Y * MathF.Sin(Orientation),
+                PixelPosition.Y * MathF.Cos(Orientation) + PixelPosition.X * MathF.Sin(Orientation));
+
+        _stampShader?.SetParameter("objCoord", GlobalPosition * UIScale * new Vector2(1, -1));
+        handle.UseShader(_stampShader);
+        handle.SetTransform(GlobalPixelPosition - PixelPosition + offset, Orientation, _textScaling);
+        base.Draw(handle);
+
+        // Restore a sane transform+shader
+        handle.SetTransform(Matrix3.Identity);
+        handle.UseShader(null);
+    }
+}