BUG: fix minpos handling and other log ticker problems

efiring · efiring · commit 6f53d3d0b0e4 · 2016-12-08T22:04:41.000-10:00
Closes #7595, #7493, #7587. Bbox._minpos is now initialized to [np.inf, np.inf] instead of [1e-7, 1e-7]. Old code with a colorbar in which the formatter is set to a LogFormatter and a SymlogNorm is used now works again (although the results are better in 2.0 if the colorbar is left to handle the formatter automatically). LogLocator now has its own nonsingular() method which provides a reasonable starting point for a log axis when no data have been plotted.
diff --git a/lib/matplotlib/scale.py b/lib/matplotlib/scale.py
@@ -264,6 +264,10 @@ def limit_range_for_scale(self, vmin, vmax, minpos):
         """
         Limit the domain to positive values.
         """
+        if not np.isfinite(minpos):
+            minpos = 1e-300  # This value should rarely if ever
+                             # end up with a visible effect.
+
         return (minpos if vmin <= 0 else vmin,
                 minpos if vmax <= 0 else vmax)
 
diff --git a/lib/matplotlib/ticker.py b/lib/matplotlib/ticker.py
@@ -906,6 +906,16 @@ def set_locs(self, locs=None):
             except AttributeError:
                 pass
 
+        if vmin > vmax:
+            vmin, vmax = vmax, vmin
+
+        if linthresh is None and vmin <= 0:
+            # It's probably a colorbar with
+            # a format kwarg setting a LogFormatter in the manner
+            # that worked with 1.5.x, but that doesn't work now.
+            self._sublabels = set((1,))  # label powers of base
+            return
+
         if linthresh is not None:  # symlog
             # Only compute the number of decades in the logarithmic part of the
             # axis
@@ -938,7 +948,7 @@ def __call__(self, x, pos=None):
         Return the format for tick val `x`.
         """
         b = self._base
-        if x == 0.0:
+        if x == 0.0:  # Symlog
             return '0'
         sign = np.sign(x)
         x = abs(x)
@@ -1999,36 +2009,41 @@ def view_limits(self, vmin, vmax):
         'Try to choose the view limits intelligently'
         b = self._base
 
-        if vmax < vmin:
-            vmin, vmax = vmax, vmin
+        vmin, vmax = self.nonsingular(vmin, vmax)
 
         if self.axis.axes.name == 'polar':
             vmax = math.ceil(math.log(vmax) / math.log(b))
             vmin = b ** (vmax - self.numdecs)
-            return vmin, vmax
-
-        minpos = self.axis.get_minpos()
-
-        if minpos <= 0 or not np.isfinite(minpos):
-            raise ValueError(
-                "Data has no positive values, and therefore can not be "
-                "log-scaled.")
-
-        if vmin <= 0:
-            vmin = minpos
 
         if rcParams['axes.autolimit_mode'] == 'round_numbers':
             if not is_decade(vmin, self._base):
                 vmin = decade_down(vmin, self._base)
             if not is_decade(vmax, self._base):
                 vmax = decade_up(vmax, self._base)
 
-            if vmin == vmax:
-                vmin = decade_down(vmin, self._base)
-                vmax = decade_up(vmax, self._base)
+        return vmin, vmax
 
-        result = mtransforms.nonsingular(vmin, vmax)
-        return result
+    def nonsingular(self, vmin, vmax):
+        if not np.isfinite(vmin) or not np.isfinite(vmax):
+            return 1, 100  # initial range, no data plotted yet
+
+        if vmin > vmax:
+            vmin, vmax = vmax, vmin
+        if vmax <= 0:
+            warnings.warn(
+                "Data has no positive values, and therefore cannot be "
+                "log-scaled.")
+            return 1, 100
+
+        minpos = self.axis.get_minpos()
+        if not np.isfinite(minpos):
+            minpos = 1e-300  # This should never take effect.
+        if vmin <= 0:
+            vmin = minpos
+        if vmin == vmax:
+            vmin = decade_down(vmin, self._base)
+            vmax = decade_up(vmax, self._base)
+        return vmin, vmax
 
 
 class SymmetricalLogLocator(Locator):
diff --git a/lib/matplotlib/transforms.py b/lib/matplotlib/transforms.py
@@ -791,7 +791,7 @@ def __init__(self, points, **kwargs):
             raise ValueError('Bbox points must be of the form '
                              '"[[x0, y0], [x1, y1]]".')
         self._points = points
-        self._minpos = np.array([0.0000001, 0.0000001])
+        self._minpos = np.array([np.inf, np.inf])
         self._ignore = True
         # it is helpful in some contexts to know if the bbox is a
         # default or has been mutated; we store the orig points to
