Fix autoscaling with tiny sticky values.

anntzer · anntzer · commit 103267d74660 · 2020-06-15T19:22:24.000+02:00
diff --git a/lib/matplotlib/axes/_base.py b/lib/matplotlib/axes/_base.py
@@ -2545,15 +2545,17 @@ def handle_single_axis(scale, autoscaleon, shared_axes, interval,
             locator = axis.get_major_locator()
             x0, x1 = locator.nonsingular(x0, x1)
 
-            # Prevent margin addition from crossing a sticky value.  Small
-            # tolerances (whose values come from isclose()) must be used due to
-            # floating point issues with streamplot.
-            def tol(x): return 1e-5 * abs(x) + 1e-8
+            # Prevent margin addition from crossing a sticky value.  A small
+            # tolerance must be added due to floating point issues with
+            # streamplot; it is defined relative to x0, x1, x1-x0 but has
+            # no absolute term (e.g. "+1e-8") to avoid issues when working with
+            # datasets where all values are tiny (less than 1e-8).
+            tol = 1e-5 * max(abs(x0), abs(x1), abs(x1 - x0))
             # Index of largest element < x0 + tol, if any.
-            i0 = stickies.searchsorted(x0 + tol(x0)) - 1
+            i0 = stickies.searchsorted(x0 + tol) - 1
             x0bound = stickies[i0] if i0 != -1 else None
             # Index of smallest element > x1 - tol, if any.
-            i1 = stickies.searchsorted(x1 - tol(x1))
+            i1 = stickies.searchsorted(x1 - tol)
             x1bound = stickies[i1] if i1 != len(stickies) else None
 
             # Add the margin in figure space and then transform back, to handle
diff --git a/lib/matplotlib/tests/test_axes.py b/lib/matplotlib/tests/test_axes.py
@@ -6314,3 +6314,11 @@ def test_polar_interpolation_steps_variable_r(fig_test, fig_ref):
     l.get_path()._interpolation_steps = 100
     fig_ref.add_subplot(projection="polar").plot(
         np.linspace(0, np.pi/2, 101), np.linspace(1, 2, 101))
+
+
+@pytest.mark.style('default')
+def test_autoscale_tiny_sticky():
+    fig, ax = plt.subplots()
+    ax.bar(0, 1e-9)
+    fig.canvas.draw()
+    assert ax.get_ylim() == (0, 1.05e-9)
