Store online status of printer in the printer's metadata

It's a little bit weird with the hidden global stack system when there's a cluster of various types of printers. But it should behave the same way.

Contributes to issue CURA-8609.

cura/PrinterOutput/NetworkedPrinterOutputDevice.py

@@ -1,4 +1,4 @@
-# Copyright (c) 2018 Ultimaker B.V.
+# Copyright (c) 2021 Ultimaker B.V.
 # Cura is released under the terms of the LGPLv3 or higher.
 
 from UM.FileHandler.FileHandler import FileHandler #For typing.
@@ -114,6 +114,11 @@ class NetworkedPrinterOutputDevice(PrinterOutputDevice):
         return b"".join(file_data_bytes_list)
 
     def _update(self) -> None:
+        """
+        Update the connection state of this device.
+
+        This is called on regular intervals.
+        """
         if self._last_response_time:
             time_since_last_response = time() - self._last_response_time
         else:
@@ -127,11 +132,11 @@ class NetworkedPrinterOutputDevice(PrinterOutputDevice):
         if time_since_last_response > self._timeout_time >= time_since_last_request:
             # Go (or stay) into timeout.
             if self._connection_state_before_timeout is None:
-                self._connection_state_before_timeout = self._connection_state
+                self._connection_state_before_timeout = self.connectionState
 
             self.setConnectionState(ConnectionState.Closed)
 
-        elif self._connection_state == ConnectionState.Closed:
+        elif self.connectionState == ConnectionState.Closed:
             # Go out of timeout.
             if self._connection_state_before_timeout is not None:   # sanity check, but it should never be None here
                 self.setConnectionState(self._connection_state_before_timeout)
@@ -361,7 +366,7 @@ class NetworkedPrinterOutputDevice(PrinterOutputDevice):
 
         self._last_response_time = time()
 
-        if self._connection_state == ConnectionState.Connecting:
+        if self.connectionState == ConnectionState.Connecting:
             self.setConnectionState(ConnectionState.Connected)
 
         callback_key = reply.url().toString() + str(reply.operation())

cura/PrinterOutput/PrinterOutputDevice.py

@@ -1,11 +1,13 @@
-# Copyright (c) 2018 Ultimaker B.V.
+# Copyright (c) 2021 Ultimaker B.V.
 # Cura is released under the terms of the LGPLv3 or higher.
+
 from enum import IntEnum
 from typing import Callable, List, Optional, Union
 
 from PyQt5.QtCore import pyqtProperty, pyqtSignal, QObject, QTimer, QUrl
 from PyQt5.QtWidgets import QMessageBox
 
+import cura.CuraApplication  # Imported like this to prevent circular imports.
 from UM.Logger import Logger
 from UM.Signal import signalemitter
 from UM.Qt.QtApplication import QtApplication
@@ -120,11 +122,22 @@ class PrinterOutputDevice(QObject, OutputDevice):
         callback(QMessageBox.Yes)
 
     def isConnected(self) -> bool:
-        return self._connection_state != ConnectionState.Closed and self._connection_state != ConnectionState.Error
+        """
+        Returns whether we could theoretically send commands to this printer.
+        :return: `True` if we are connected, or `False` if not.
+        """
+        return self.connectionState != ConnectionState.Closed and self.connectionState != ConnectionState.Error
 
     def setConnectionState(self, connection_state: "ConnectionState") -> None:
-        if self._connection_state != connection_state:
+        """
+        Store the connection state of the printer.
+
+        Causes everything that displays the connection state to update its QML models.
+        :param connection_state: The new connection state to store.
+        """
+        if self.connectionState != connection_state:
             self._connection_state = connection_state
+            cura.CuraApplication.CuraApplication.getInstance().getGlobalContainerStack().setMetaDataEntry("is_online", self.isConnected())
             self.connectionStateChanged.emit(self._id)
 
     @pyqtProperty(int, constant = True)
@@ -133,6 +146,10 @@ class PrinterOutputDevice(QObject, OutputDevice):
 
     @pyqtProperty(int, notify = connectionStateChanged)
     def connectionState(self) -> "ConnectionState":
+        """
+        Get the connection state of the printer, e.g. whether it is connected, still connecting, error state, etc.
+        :return: The current connection state of this output device.
+        """
         return self._connection_state
 
     def _update(self) -> None: