Pyqtgraph automatically store ref to the last 100 plots (configurable)

qcodes/config/qcodesrc.json

@@ -5,7 +5,8 @@
     },
     "gui" :{
         "notebook": true,
-        "plotlib": "matplotlib"
+        "plotlib": "matplotlib",
+        "pyqtmaxplots": 100
     },
     "user": {}
 }

qcodes/config/qcodesrc_schema.json

@@ -41,9 +41,14 @@
                     "type": "string",
                     "enum": ["QT", "matplotlib" ],
                     "default": "matplotlib"
+                },
+                "pyqtmaxplots": {
+                    "description": "Maximum number of PyQtPlots to automatically keep in memory",
+                    "type": "integer",
+                    "default": 100
                 }
             },
-            "required":[ "notebook", "plotlib" ]
+            "required":[ "notebook", "plotlib", "pyqtmaxplots" ]
         },
         "user":{
             "type" : "object",

qcodes/plots/pyqtgraph.py

@@ -4,12 +4,13 @@
 import numpy as np
 import pyqtgraph as pg
 import pyqtgraph.multiprocess as pgmp
+from pyqtgraph.multiprocess.remoteproxy import ClosedError
 import warnings
-from collections import namedtuple
+from collections import namedtuple, deque
 
 from .base import BasePlot
 from .colors import color_cycle, colorscales
-
+import qcodes.config
 
 TransformState = namedtuple('TransformState', 'translate scale revisit')
 
@@ -37,6 +38,15 @@ class QtPlot(BasePlot):
     """
     proc = None
     rpg = None
+    # we store references to plots to keep the garbage collections from
+    # destroying the windows. To keep memory consumption within bounds we
+    # limit this to an arbitrary number of plots here using a deque
+    # The issue is that even when closing a window it's difficult to
+    # remove it from the list. This could potentially be done with a
+    # close event on win but this is difficult with remote proxy process
+    # as the list of plots lives in the main process and the plot locally
+    # in a remote process
+    plots = deque(maxlen=qcodes.config['gui']['pyqtmaxplots'])
 
     def __init__(self, *args, figsize=(1000, 600), interval=0.25,
                  window_title='', theme=((60, 60, 60), 'w'), show_window=True, remote=True, **kwargs):
@@ -55,7 +65,16 @@ def __init__(self, *args, figsize=(1000, 600), interval=0.25,
         else:
             # overrule the remote pyqtgraph class
             self.rpg = pg
-        self.win = self.rpg.GraphicsWindow(title=window_title)
+        try:
+            self.win = self.rpg.GraphicsWindow(title=window_title)
+        except ClosedError as err:
+            # the remote process may have crashed. In that case try restarting
+            # it
+            if remote:
+                self._init_qt()
+                self.win = self.rpg.GraphicsWindow(title=window_title)
+            else:
+                raise err
         self.win.setBackground(theme[1])
         self.win.resize(*figsize)
         self.subplots = [self.add_subplot()]
@@ -66,13 +85,16 @@ def __init__(self, *args, figsize=(1000, 600), interval=0.25,
         if not show_window:
             self.win.hide()
 
-    def _init_qt(self):
+        self.plots.append(self)
+
+    @classmethod
+    def _init_qt(cls):
         # starting the process for the pyqtgraph plotting
         # You do not want a new process to be created every time you start a
         # run, so this only starts once and stores the process in the class
         pg.mkQApp()
-        self.__class__.proc = pgmp.QtProcess()  # pyqtgraph multiprocessing
-        self.__class__.rpg = self.proc._import('pyqtgraph')
+        cls.proc = pgmp.QtProcess()  # pyqtgraph multiprocessing
+        cls.rpg = cls.proc._import('pyqtgraph')
 
     def clear(self):
         """