FIX: quiver key pivot location

tacaswell · tacaswell · commit 34d601f190a8 · 2015-12-04T22:06:32.000-05:00
In PR #3955 / af17051 the quiver pivot location was normalized to be 'tip', 'tail', or 'middle' internally. The key 'mid' is now normalized to 'middle'. The quiver key code circumvents the normalization and was setting `Quiver.pivot' to 'mid', which fell back to the default behavior of pivoting on the tail when the quiver key is drawn. closes #5613
diff --git a/lib/matplotlib/quiver.py b/lib/matplotlib/quiver.py
@@ -228,7 +228,7 @@ class QuiverKey(martist.Artist):
     """ Labelled arrow for use as a quiver plot scale key."""
     halign = {'N': 'center', 'S': 'center', 'E': 'left', 'W': 'right'}
     valign = {'N': 'bottom', 'S': 'top', 'E': 'center', 'W': 'center'}
-    pivot = {'N': 'mid', 'S': 'mid', 'E': 'tip', 'W': 'tail'}
+    pivot = {'N': 'middle', 'S': 'middle', 'E': 'tip', 'W': 'tail'}
 
     def __init__(self, Q, X, Y, U, label, **kw):
         martist.Artist.__init__(self)
@@ -708,6 +708,10 @@ def _h_arrows(self, length):
             X = X - X[:, 3, np.newaxis]   # numpy bug? using -= does not
                                           # work here unless we multiply
                                           # by a float first, as with 'mid'.
+        elif self.pivot != 'tail':
+            raise ValueError(("Quiver.pivot must have value in {{'middle', "
+                              "'tip', 'tail'}} not {}").format(self.pivot))
+
         tooshort = length < self.minlength
         if tooshort.any():
             # Use a heptagonal dot:
diff --git a/lib/matplotlib/tests/baseline_images/test_quiver/quiver_key_pivot.png b/lib/matplotlib/tests/baseline_images/test_quiver/quiver_key_pivot.png
diff --git a/lib/matplotlib/tests/test_quiver.py b/lib/matplotlib/tests/test_quiver.py
@@ -92,6 +92,22 @@ def test_quiver_copy():
     assert q0.V[0] == 2.0
 
 
+@image_comparison(baseline_images=['quiver_key_pivot'],
+                  extensions=['png'], remove_text=True)
+def test_quiver_key_pivot():
+    fig, ax = plt.subplots()
+
+    u, v = np.mgrid[0:2*np.pi:10j, 0:2*np.pi:10j]
+
+    q = ax.quiver(np.sin(u), np.cos(v))
+    ax.set_xlim(-2, 11)
+    ax.set_ylim(-2, 11)
+    ax.quiverkey(q, 0.5, 1, 1, 'N', labelpos='N')
+    ax.quiverkey(q, 1, 0.5, 1, 'E', labelpos='E')
+    ax.quiverkey(q, 0.5, 0, 1, 'S', labelpos='S')
+    ax.quiverkey(q, 0, 0.5, 1, 'W', labelpos='W')
+
+
 if __name__ == '__main__':
     import nose
     nose.runmodule()
