Merge pull request matplotlib#30162 from QuLogic/nan-spacing

TST: Fix runtime error checking NaN input to format_cursor_data

Author: timhoffm

lib/matplotlib/cbook.py

@@ -2228,6 +2228,9 @@ def _g_sig_digits(value, delta):
     Return the number of significant digits to %g-format *value*, assuming that
     it is known with an error of *delta*.
     """
+    # For inf or nan, the precision doesn't matter.
+    if not math.isfinite(value):
+        return 0
     if delta == 0:
         if value == 0:
             # if both value and delta are 0, np.spacing below returns 5e-324
@@ -2241,11 +2244,10 @@ def _g_sig_digits(value, delta):
     # digits before the decimal point (floor(log10(45.67)) + 1 = 2): the total
     # is 4 significant digits.  A value of 0 contributes 1 "digit" before the
     # decimal point.
-    # For inf or nan, the precision doesn't matter.
     return max(
         0,
         (math.floor(math.log10(abs(value))) + 1 if value else 1)
-        - math.floor(math.log10(delta))) if math.isfinite(value) else 0
+        - math.floor(math.log10(delta)))
 
 
 def _unikey_or_keysym_to_mplkey(unikey, keysym):