Improve formatting of imshow() cursor data when a colorbar exists.

anntzer · anntzer · commit 02a0455ac722 · 2018-10-09T17:05:03.000+02:00
When a colorbar exists, use its formatter to format cursor data.
For example, after
```
imshow([[10000, 10001]]); colorbar()
```
currently the cursor data on either pixel is rendered as 1e4, but after
this patch it becomes 0.0+1e4 / 1.0+1e4, or 10000.0 / 10001.0 if
`rcParams["axes.formatter.useoffset"]` is set to False.  (Even though
the version with the offset text may not be the most esthetic, it's
clearly more informative than the current behavior...)

It would be nice if this worked even for ScalarMappables that don't
have a colorbar; this may include extracting the Formatter selection
code out of the colorbar code into something generally applicable to
ScalarMappables, or just generating a hidden colorbar "on-the-fly" if
needed just for the purpose of getting its Formatter.
diff --git a/lib/matplotlib/artist.py b/lib/matplotlib/artist.py
@@ -1,6 +1,7 @@
 from collections import OrderedDict, namedtuple
 from functools import wraps
 import inspect
+from numbers import Number
 import re
 import warnings
 
@@ -1159,8 +1160,8 @@ def format_cursor_data(self, data):
             data[0]
         except (TypeError, IndexError):
             data = [data]
-        data_str = ', '.join('{:0.3g}'.format(item) for item in data if
-                   isinstance(item, (np.floating, np.integer, int, float)))
+        data_str = ', '.join('{:0.3g}'.format(item) for item in data
+                             if isinstance(item, Number))
         return "[" + data_str + "]"
 
     @property
diff --git a/lib/matplotlib/cbook/__init__.py b/lib/matplotlib/cbook/__init__.py
@@ -302,11 +302,17 @@ def local_over_kwdict(local_var, kwargs, *keys):
 
 
 def strip_math(s):
-    """remove latex formatting from mathtext"""
-    remove = (r'\mathdefault', r'\rm', r'\cal', r'\tt', r'\it', '\\', '{', '}')
-    s = s[1:-1]
-    for r in remove:
-        s = s.replace(r, '')
+    """
+    Remove latex formatting from mathtext.
+
+    Only handles fully math and fully non-math strings.
+    """
+    if s[:1] == s[-1:] == "$":
+        s = s[1:-1]
+        remove = [
+            r'\mathdefault', r'\rm', r'\cal', r'\tt', r'\it', '\\', '{', '}']
+        for r in remove:
+            s = s.replace(r, '')
     return s
 
 
diff --git a/lib/matplotlib/image.py b/lib/matplotlib/image.py
@@ -907,6 +907,13 @@ def get_cursor_data(self, event):
         else:
             return arr[i, j]
 
+    def format_cursor_data(self, data):
+        if self.colorbar:
+            return (cbook.strip_math(self.colorbar.formatter(data))
+                    + cbook.strip_math(self.colorbar.formatter.get_offset()))
+        else:
+            return super().format_cursor_data(data)
+
 
 class NonUniformImage(AxesImage):
     def __init__(self, ax, *, interpolation='nearest', **kwargs):
