From 605fe44477ed102bfe3d9dbaee01ea8971a7ce84 Mon Sep 17 00:00:00 2001
From: Derek Homeier <dhomeie@gwdg.de>
Date: Thu, 30 Dec 2021 16:49:40 +0100
Subject: [PATCH] Experimental `rotation.setter` for PolygonPixelRegion

---
 regions/shapes/polygon.py            | 19 +++++++++++++++++++
 regions/shapes/tests/test_polygon.py | 16 ++++++++++++++++
 2 files changed, 35 insertions(+)

diff --git a/regions/shapes/polygon.py b/regions/shapes/polygon.py
index 4e826c68..2b1ade90 100644
--- a/regions/shapes/polygon.py
+++ b/regions/shapes/polygon.py
@@ -70,6 +70,7 @@ def __init__(self, vertices, meta=None, visual=None,
         self.visual = visual or RegionVisual()
         self.origin = origin
         self.vertices = vertices + origin
+        self._rotation = 0.0 * u.degree
 
     @property
     def area(self):
@@ -301,6 +302,24 @@ def rotate(self, center, angle):
         vertices = self.vertices.rotate(center, angle)
         return self.copy(vertices=vertices)
 
+    @property
+    def rotation(self):
+        """
+        Rotation angle to apply in-place rotations (operating on this instance).
+        Since `.setter` will apply the rotation directly on the vertices, this
+        value will always be reset to 0.
+        """
+        return self._rotation
+
+    @rotation.setter
+    def rotation(self, angle):
+        self.vertices = self.vertices.rotate(self.centroid, angle - self._rotation)
+        self._rotation = 0.0 * u.degree
+        if hasattr(self, '_mpl_selector'):
+            self._mpl_selector.verts = list(zip(self.vertices.x, self.vertices.y))
+            if getattr(self, '_mpl_selector_callback', None) is not None:
+                self._mpl_selector_callback(self)
+
 
 class RegularPolygonPixelRegion(PolygonPixelRegion):
     """
diff --git a/regions/shapes/tests/test_polygon.py b/regions/shapes/tests/test_polygon.py
index 0d1dc61f..107d00a6 100644
--- a/regions/shapes/tests/test_polygon.py
+++ b/regions/shapes/tests/test_polygon.py
@@ -115,6 +115,22 @@ def test_origin(self):
         reg2 = PolygonPixelRegion(relverts, origin=origin)
         assert_equal(reg1.vertices, reg2.vertices)
 
+    def test_rotation(self):
+        """Test 'in-place' rotation of polygon instance, including full rotation"""
+        self.reg.rotation = 90 * u.deg
+        assert_allclose(self.reg.vertices.x, [8/3., 8/3., -1/3.], rtol=1e-9)
+        assert_allclose(self.reg.vertices.y, [4/3., 10/3., 4/3.], rtol=1e-9)
+        assert_allclose(self.reg.rotation, 0 * u.deg, rtol=1e-9)
+
+        self.reg.rotation = 90 * u.deg
+        assert_allclose(self.reg.vertices.x, [7/3., 1/3., 7/3.], rtol=1e-9)
+        assert_allclose(self.reg.vertices.y, [3, 3, 0], rtol=1e-9)
+
+        self.reg.rotation = 180 * u.deg
+        assert_allclose(self.reg.vertices.x, [1, 3, 1], rtol=1e-9)
+        assert_allclose(self.reg.vertices.y, [1, 1, 4], rtol=1e-9)
+        assert_allclose(self.reg.rotation, 0 * u.deg, rtol=1e-9)
+
 
 class TestPolygonSkyRegion(BaseTestSkyRegion):