Backport PR #13689: BUG: fix scaling of quiverkey when quiver scale_units='xy'

tacaswell · MeeseeksDev[bot] · commit 117f4ac03f77 · 2019-03-18T20:00:44.000Z
diff --git a/lib/matplotlib/quiver.py b/lib/matplotlib/quiver.py
@@ -304,8 +304,11 @@ def _init(self):
             # Hack: save and restore the Umask
             _mask = self.Q.Umask
             self.Q.Umask = ma.nomask
+            u = self.U * np.cos(np.radians(self.angle))
+            v = self.U * np.sin(np.radians(self.angle))
+            angle = self.Q.angles if isinstance(self.Q.angles, str) else 'uv'
             self.verts = self.Q._make_verts(
-                np.array([self.U]), np.zeros(1), self.angle)
+                np.array([u]), np.array([v]), angle)
             self.Q.Umask = _mask
             self.Q.pivot = _pivot
             kw = self.Q.polykw
diff --git a/lib/matplotlib/tests/baseline_images/test_quiver/quiver_key_xy.png b/lib/matplotlib/tests/baseline_images/test_quiver/quiver_key_xy.png
diff --git a/lib/matplotlib/tests/test_quiver.py b/lib/matplotlib/tests/test_quiver.py
@@ -129,6 +129,31 @@ def test_quiver_key_pivot():
     ax.quiverkey(q, 0, 0.5, 1, 'W', labelpos='W')
 
 
+@image_comparison(baseline_images=['quiver_key_xy'],
+                  extensions=['png'], remove_text=True)
+def test_quiver_key_xy():
+    # With scale_units='xy', ensure quiverkey still matches its quiver.
+    # Note that the quiver and quiverkey lengths depend on the axes aspect
+    # ratio, and that with angles='xy' their angles also depend on the axes
+    # aspect ratio.
+    X = np.arange(8)
+    Y = np.zeros(8)
+    angles = X * (np.pi / 4)
+    uv = np.exp(1j * angles)
+    U = uv.real
+    V = uv.imag
+    fig, axs = plt.subplots(2)
+    for ax, angle_str in zip(axs, ('uv', 'xy')):
+        ax.set_xlim(-1, 8)
+        ax.set_ylim(-0.2, 0.2)
+        q = ax.quiver(X, Y, U, V, pivot='middle',
+                      units='xy', width=0.05,
+                      scale=2, scale_units='xy',
+                      angles=angle_str)
+        for x, angle in zip((0.2, 0.5, 0.8), (0, 45, 90)):
+            ax.quiverkey(q, X=x, Y=0.8, U=1, angle=angle, label='', color='b')
+
+
 @image_comparison(baseline_images=['barbs_test_image'],
                   extensions=['png'], remove_text=True)
 def test_barbs():
