From e29f86578f120fda2281cfddb7429d03470fe29b Mon Sep 17 00:00:00 2001
From: Luke Campagnola <luke.campagnola@gmail.com>
Date: Thu, 27 May 2021 11:51:06 -0400
Subject: [PATCH] Revert Point.angle behavior change (#1806)

* Revert behavior change of Point.angle

* Propagate Point.angle revert
---
 examples/fractal.py            | 2 +-
 pyqtgraph/Point.py             | 6 +++---
 pyqtgraph/SRTTransform.py      | 2 +-
 pyqtgraph/graphicsItems/ROI.py | 8 ++++----
 pyqtgraph/tests/test_Point.py  | 2 +-
 5 files changed, 10 insertions(+), 10 deletions(-)

diff --git a/examples/fractal.py b/examples/fractal.py
index 38248bf4..b03ffdb8 100644
--- a/examples/fractal.py
+++ b/examples/fractal.py
@@ -56,7 +56,7 @@ def update():
         p2 = pts[i+1]
         v2 = p2 - p1
         t = p1 - pts[0]
-        r = v1.angle(v2)
+        r = v2.angle(v1)
         s = v2.length() / l1
         trs.append(pg.SRTTransform({'pos': t, 'scale': (s, s), 'angle': r}))
 
diff --git a/pyqtgraph/Point.py b/pyqtgraph/Point.py
index 973226dd..4fffbf3d 100644
--- a/pyqtgraph/Point.py
+++ b/pyqtgraph/Point.py
@@ -107,7 +107,7 @@ class Point(QtCore.QPointF):
     
     def angle(self, a, units="degrees"):
         """
-        Returns the angle in degrees between this vector and the vector a.
+        Returns the angle in degrees from the vector a to self.
         
         Parameters
         ----------
@@ -120,9 +120,9 @@ class Point(QtCore.QPointF):
         Returns
         -------
         float
-            The angle between the two points
+            The angle between two vectors
         """
-        rads = atan2(a.y(), a.x()) - atan2(self.y(), self.x())
+        rads = atan2(self.y(), self.x()) - atan2(a.y(), a.x())
         if units == "radians":
             return rads
         return degrees(rads)
diff --git a/pyqtgraph/SRTTransform.py b/pyqtgraph/SRTTransform.py
index e40fa40f..110186e1 100644
--- a/pyqtgraph/SRTTransform.py
+++ b/pyqtgraph/SRTTransform.py
@@ -66,7 +66,7 @@ class SRTTransform(QtGui.QTransform):
         dp3 = Point(p3-p1)
         
         ## detect flipped axes
-        if dp3.angle(dp2, units="radians") > 0:
+        if dp2.angle(dp3, units="radians") > 0:
             da = 0
             sy = -1.0
         else:
diff --git a/pyqtgraph/graphicsItems/ROI.py b/pyqtgraph/graphicsItems/ROI.py
index d9843167..dcf4dfdc 100644
--- a/pyqtgraph/graphicsItems/ROI.py
+++ b/pyqtgraph/graphicsItems/ROI.py
@@ -936,7 +936,7 @@ class ROI(GraphicsObject):
                 return
             
             ## determine new rotation angle, constrained if necessary
-            ang = newState['angle'] - lp1.angle(lp0)
+            ang = newState['angle'] - lp0.angle(lp1)
             if ang is None:  ## this should never happen..
                 return
             if self.rotateSnap or (modifiers & QtCore.Qt.ControlModifier):
@@ -972,7 +972,7 @@ class ROI(GraphicsObject):
             except OverflowError:
                 return
             
-            ang = newState['angle'] - lp1.angle(lp0)
+            ang = newState['angle'] - lp0.angle(lp1)
             if ang is None:
                 return
             if self.rotateSnap or (modifiers & QtCore.Qt.ControlModifier):
@@ -1663,7 +1663,7 @@ class LineROI(ROI):
         pos2 = Point(pos2)
         d = pos2-pos1
         l = d.length()
-        ra = d.angle(Point(1, 0), units="radians")
+        ra = Point(1, 0).angle(d, units="radians")
         c = Point(-width/2. * sin(ra), -width/2. * cos(ra))
         pos1 = pos1 + c
         
@@ -2358,7 +2358,7 @@ class RulerROI(LineSegmentROI):
 
         vec = Point(h2) - Point(h1)
         length = vec.length()
-        angle = Point(1, 0).angle(vec)
+        angle = vec.angle(Point(1, 0))
 
         pvec = p2 - p1
         pvecT = Point(pvec.y(), -pvec.x())
diff --git a/pyqtgraph/tests/test_Point.py b/pyqtgraph/tests/test_Point.py
index a8252e11..ea9a95ed 100644
--- a/pyqtgraph/tests/test_Point.py
+++ b/pyqtgraph/tests/test_Point.py
@@ -13,7 +13,7 @@ angles = [
 def test_Point_angle(p1, p2, angle):
 	p1 = pg.Point(*p1)
 	p2 = pg.Point(*p2)
-	assert p1.angle(p2) == angle
+	assert p2.angle(p1) == angle
 
 
 inits = [