Make figure identifier unique

src/python_spectrometer/_plot_manager.py

@@ -2,6 +2,7 @@
 import contextlib
 import os
 import warnings
+import weakref
 from itertools import compress
 from typing import Dict, Any, Optional, Mapping, Tuple, ContextManager, Iterable, Union, List
 
@@ -18,6 +19,8 @@ _styleT = Union[None, _styleT, List[_styleT]]
 
 
 class PlotManager:
+    __instances = weakref.WeakSet()
+
     # TODO: blit?
     PLOT_TYPES = ('main', 'cumulative', 'time')
     LINE_TYPES = ('processed', 'raw')
@@ -68,7 +71,7 @@ class PlotManager:
         self.legend_kw = legend_kw or dict()
 
         self.legend_kw.setdefault('loc', 'upper right')
-        self.figure_kw.setdefault('num', 'Spectrometer')
+        self.figure_kw.setdefault('num', f'Spectrometer {len(self.__instances) + 1}')
         if not any('layout' in key for key in self.figure_kw.keys()):
             # depending on the matplotlib version, this setting is either
             # layout='tight' or tight_layout=True
@@ -76,6 +79,11 @@ class PlotManager:
         if self.subplot_kw.pop('sharex', None) is not None:
             warnings.warn('sharex in subplot_kw not negotiable, dropping', UserWarning)
 
+        # Keep track of instances that are alive for figure counting
+        self.__instances.add(self)
+        # TODO: this somehow never executes
+        weakref.finalize(self, self.__instances.discard, self)
+
     def is_fig_open(self) -> bool:
         """Is the figure currently open, pending all events?"""
         # Need to flush possible close events before we can be sure!