Make set_x/ymargin() update axes limits, just like margins().

anntzer · anntzer · commit 2292f7be0731 · 2020-05-06T15:11:43.000+02:00
Previously, setting the margins via set_x/ymargin() would not update
axes limits, unlike calling margins().  This appears to be a simple
oversight.

The change in collections.py is necessary because the difference in
timing at which autoscale is executed now exposed a floating point
inaccuracy (which gets amplified by the old round_numbers autolimits
mode).
diff --git a/lib/matplotlib/axes/_base.py b/lib/matplotlib/axes/_base.py
@@ -2294,6 +2294,7 @@ def set_xmargin(self, m):
         if m <= -0.5:
             raise ValueError("margin must be greater than -0.5")
         self._xmargin = m
+        self._request_autoscale_view(scalex=True, scaley=False)
         self.stale = True
 
     def set_ymargin(self, m):
@@ -2316,6 +2317,7 @@ def set_ymargin(self, m):
         if m <= -0.5:
             raise ValueError("margin must be greater than -0.5")
         self._ymargin = m
+        self._request_autoscale_view(scalex=False, scaley=True)
         self.stale = True
 
     def margins(self, *margins, x=None, y=None, tight=True):
@@ -2386,15 +2388,13 @@ def margins(self, *margins, x=None, y=None, tight=True):
                 cbook._warn_external(f'ignoring tight={tight!r} in get mode')
             return self._xmargin, self._ymargin
 
+        if tight is not None:
+            self._tight = tight
         if x is not None:
             self.set_xmargin(x)
         if y is not None:
             self.set_ymargin(y)
 
-        self._request_autoscale_view(
-            tight=tight, scalex=(x is not None), scaley=(y is not None)
-        )
-
     def set_rasterization_zorder(self, z):
         """
         Parameters
diff --git a/lib/matplotlib/tests/test_axes.py b/lib/matplotlib/tests/test_axes.py
@@ -4582,6 +4582,14 @@ def test_margins():
                               ymax + (ymax - ymin) * 0.5)
 
 
+def test_set_margin_updates_limits():
+    mpl.style.use("default")
+    fig, ax = plt.subplots()
+    ax.plot([1, 2], [1, 2])
+    ax.set(xscale="log", xmargin=0)
+    assert ax.get_xlim() == (1, 2)
+
+
 def test_length_one_hist():
     fig, ax = plt.subplots()
     ax.hist(1)
