Make the formatting more explicit

jkseppan · jkseppan · commit 9225aec962de · 2020-07-27T19:36:55.000+03:00
This avoids exponential notation (which is supported by PS but who
knows how all the different parsers react to it) and trailing zeros,
so we don't unnecessarily increase the size of fonts that have a
nice [0.001 0 0 0.001] matrix.

Encapsulate the formatting operation in a cbook function and give
it a unit test.
diff --git a/lib/matplotlib/cbook/__init__.py b/lib/matplotlib/cbook/__init__.py
@@ -2383,3 +2383,11 @@ def _setup_new_guiapp():
     except OSError:
         _c_internal_utils.Win32_SetCurrentProcessExplicitAppUserModelID(
             "matplotlib")
+
+
+def format_approx(number, precision):
+    """
+    Format the number with at most the number of decimals given as precision.
+    Remove trailing zeros and possibly the decimal point.
+    """
+    return f'{number:.{precision}f}'.rstrip('0').rstrip('.') or '0'
diff --git a/lib/matplotlib/tests/test_cbook.py b/lib/matplotlib/tests/test_cbook.py
@@ -741,3 +741,15 @@ def verify_pre_post_state(obj):
         assert a.static == 'static'
 
     verify_pre_post_state(a)
+
+
+def test_format_approx():
+    f = cbook.format_approx
+    assert f(0, 1) == '0'
+    assert f(0, 2) == '0'
+    assert f(0, 3) == '0'
+    assert f(-0.0123, 1) == '-0'
+    assert f(1e-7, 5) == '0'
+    assert f(0.0012345600001, 5) == '0.00123'
+    assert f(-0.0012345600001, 5) == '-0.00123'
+    assert f(0.0012345600001, 8) == f(0.0012345600001, 10) == '0.00123456'
diff --git a/lib/matplotlib/type1font.py b/lib/matplotlib/type1font.py
@@ -29,6 +29,8 @@
 
 import numpy as np
 
+from matplotlib.cbook import format_approx
+
 
 # token types
 _TokenType = enum.Enum('_TokenType',
@@ -269,7 +271,7 @@ def fontmatrix(array):
             array[::2] = newmatrix[0:3, 0]
             array[1::2] = newmatrix[0:3, 1]
             return (
-                '[' + ' '.join(f'{x:.5g}' for x in array) + ']'
+                '[%s]' % ' '.join(format_approx(x, 6) for x in array)
             ).encode('ascii')
 
         def replace(fun):
