From 3b169d6513eba1c9fd82b2d10c4747e65d6062e9 Mon Sep 17 00:00:00 2001
From: Thomas A Caswell <tcaswell@gmail.com>
Date: Wed, 16 Nov 2016 08:59:20 -0500
Subject: [PATCH] FIX: better handle margins on ax.bar

Cancel margin on the proper sides depending on if the bar is positive,
negative, or mixed.
---
 lib/matplotlib/axes/_axes.py | 56 +++++++++++++++++++++++++++++++-----
 1 file changed, 49 insertions(+), 7 deletions(-)

diff --git a/lib/matplotlib/axes/_axes.py b/lib/matplotlib/axes/_axes.py
index 59ccbc7fc910..9a95ad74750e 100644
--- a/lib/matplotlib/axes/_axes.py
+++ b/lib/matplotlib/axes/_axes.py
@@ -2080,6 +2080,55 @@ def make_iterable(x):
             raise ValueError("incompatible sizes: argument 'bottom' "
                              "must be length %d or scalar" % nbars)
 
+        margins = {}
+
+        if orientation == 'vertical':
+            # base case of 'simple' bar plot
+            use_bottom_margin = False
+            use_top_margin = True
+            print(use_bottom_margin, use_top_margin)
+            # if negative height bars, do not pin the bottom
+            if any(h < 0 for h in height):
+                use_bottom_margin = True
+                use_top_margin = True
+            print(use_bottom_margin, use_top_margin)
+
+            # if all bars are negative pin top, but not bottom
+            if all(h < 0 for h in height):
+                use_bottom_margin = True
+                use_top_margin = False
+
+            print(use_bottom_margin, use_top_margin)
+            # if non-trivial bottom, do not pin the bottom
+            if _bottom is not None:
+                use_bottom_margin = True
+                use_top_margin = True
+            print(use_bottom_margin, use_top_margin)
+            margins = {'bottom': use_bottom_margin,
+                       'top': use_top_margin}
+
+        elif orientation == 'horizontal':
+            # base case of 'simple' bar plot
+            use_left_margin = False
+            use_right_margin = True
+            # if negative height bars, do not pin the bottom
+            if any(w < 0 for w in width):
+                use_left_margin = True
+                use_right_margin = True
+
+            # if all bars are negative pin top, but not bottom
+            if all(w < 0 for w in width):
+                use_left_margin = True
+                use_right_margin = False
+
+            # if non-trivial left, do not pin the anything
+            if _left is not None:
+                use_left_margin = True
+                use_right_margin = True
+
+            margins = {'left': use_left_margin,
+                       'right': use_right_margin}
+
         patches = []
 
         # lets do some conversions now since some types cannot be
@@ -2096,13 +2145,6 @@ def make_iterable(x):
             if yerr is not None:
                 yerr = self.convert_yunits(yerr)
 
-        margins = {}
-
-        if orientation == 'vertical':
-            margins = {'bottom': False}
-        elif orientation == 'horizontal':
-            margins = {'left': False}
-
         if align == 'center':
             if orientation == 'vertical':
                 left = [left[i] - width[i] / 2. for i in xrange(len(left))]