Fix ScalarFormatter.format_ticks for non-ordered tick locations.

anntzer · anntzer · commit 3987d942babd · 2021-06-28T19:18:07.000+02:00
Non-ordered "ticks" locations can be used when using ScalarFormatter to
format contour lines.  Perhaps ContourLabeler.get_text could arrange for
the "ticks" to be ordered, but it's much easier to just support
non-ordered ticks in ScalarFormatter.
diff --git a/lib/matplotlib/tests/test_contour.py b/lib/matplotlib/tests/test_contour.py
@@ -464,3 +464,12 @@ def test_contour_line_start_on_corner_edge():
     cbar = fig.colorbar(filled)
     lines = ax.contour(x, y, z, corner_mask=True, colors='k')
     cbar.add_lines(lines)
+
+
+def test_contour_autolabel_beyond_powerlimits():
+    ax = plt.figure().add_subplot()
+    cs = plt.contour(np.geomspace(1e-6, 1e-4, 100).reshape(10, 10),
+                     levels=[.25e-5, 1e-5, 4e-5])
+    ax.clabel(cs)
+    # Currently, the exponent is missing, but that may be fixed in the future.
+    assert {text.get_text() for text in ax.texts} == {"0.25", "1.00", "4.00"}
diff --git a/lib/matplotlib/ticker.py b/lib/matplotlib/ticker.py
@@ -817,10 +817,7 @@ def _set_order_of_magnitude(self):
         if self.offset:
             oom = math.floor(math.log10(vmax - vmin))
         else:
-            if locs[0] > locs[-1]:
-                val = locs[0]
-            else:
-                val = locs[-1]
+            val = locs.max()
             if val == 0:
                 oom = 0
             else:
