From 668d369943b383ca91cd8222730e1179be99df89 Mon Sep 17 00:00:00 2001
From: Camden Dixie O'Brien <cdo@wip.sh>
Date: Thu, 29 May 2025 01:14:30 +0100
Subject: [PATCH] Define rotation transform

---
 drawing.lisp | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drawing.lisp b/drawing.lisp
index 42349fd..9c2b975 100644
--- a/drawing.lisp
+++ b/drawing.lisp
@@ -61,6 +61,10 @@
                   :y-transform (* scale-factor y)
                   :scalar-transform (* scale-factor s))
 
+(define-transform rotate (theta)
+                  :x-transform (- (* x (cos theta)) (* y (sin theta)))
+                  :y-transform (+ (* x (sin theta)) (* y (cos theta))))
+
 (defun overlay (&rest drawings)
   (apply #'append drawings))