Split error checking into smaller sub-tasks

CURA-5059

Split stack error checking into smaller sub-tasks so running them on the Qt
thread will not block GUI updates from happening for too long.

cura/Machines/MachineErrorChecker.py

@@ -0,0 +1,184 @@
+# Copyright (c) 2018 Ultimaker B.V.
+# Cura is released under the terms of the LGPLv3 or higher.
+
+from collections import deque
+
+from PyQt5.QtCore import QObject, QTimer, pyqtSignal, pyqtProperty
+
+from UM.Application import Application
+from UM.Logger import Logger
+
+
+#
+# This class performs setting error checks for the currently active machine.
+#
+# The whole error checking process is pretty heavy which can take ~0.5 secs, so it can cause GUI to lag.
+# The idea here is to split the whole error check into small tasks, each of which only checks a single setting key
+# in a stack. According to my profiling results, the maximal runtime for such a sub-task is <0.03 secs, which should
+# be good enough. Moreover, if any changes happened to the machine, we can cancel the check in progress without wait
+# for it to finish the complete work.
+#
+class MachineErrorChecker(QObject):
+
+    def __init__(self, parent = None):
+        super().__init__(parent)
+
+        self._global_stack = None
+
+        self._has_errors = True  # Result of the error check, indicating whether there are errors in the stack
+        self._error_keys = set()  # A set of settings keys that have errors
+        self._error_keys_in_progress = set()  # The variable that stores the results of the currently in progress check
+
+        self._stacks_to_check = None  # a FIFO queue of stacks to check for errors
+        self._keys_to_check = None  # a FIFO queue of setting keys to check for errors
+
+        self._need_to_check = False  # Whether we need to schedule a new check or not. This flag is set when a new
+                                     # error check needs to take place while there is already one running at the moment.
+        self._check_in_progress = False  # Whether there is an error check running in progress at the moment.
+
+        self._application = Application.getInstance()
+        self._machine_manager = self._application.getMachineManager()
+
+        # This timer delays the starting of error check so we can react less frequently if the user is frequently
+        # changing settings.
+        self._error_check_timer = QTimer(self)
+        self._error_check_timer.setInterval(300)
+        self._error_check_timer.setSingleShot(True)
+
+    def initialize(self):
+        self._error_check_timer.timeout.connect(self._rescheduleCheck)
+
+        # Reconnect all signals when the active machine gets changed.
+        self._machine_manager.globalContainerChanged.connect(self._onMachineChanged)
+
+        # Whenever the machine settings get changed, we schedule an error check.
+        self._machine_manager.globalContainerChanged.connect(self.startErrorCheck)
+        self._machine_manager.globalValueChanged.connect(self.startErrorCheck)
+
+        self._onMachineChanged()
+
+    def _onMachineChanged(self):
+        if self._global_stack:
+            self._global_stack.propertyChanged.disconnect(self.startErrorCheck)
+            self._global_stack.containersChanged.disconnect(self.startErrorCheck)
+
+            for extruder in self._global_stack.extruders.values():
+                extruder.propertyChanged.disconnect(self.startErrorCheck)
+                extruder.containersChanged.disconnect(self.startErrorCheck)
+
+        self._global_stack = self._machine_manager.activeMachine
+
+        if self._global_stack:
+            self._global_stack.propertyChanged.connect(self.startErrorCheck)
+            self._global_stack.containersChanged.connect(self.startErrorCheck)
+
+            for extruder in self._global_stack.extruders.values():
+                extruder.propertyChanged.connect(self.startErrorCheck)
+                extruder.containersChanged.connect(self.startErrorCheck)
+
+    hasErrorUpdated = pyqtSignal()
+    needToWaitForResultChanged = pyqtSignal()
+    errorCheckFinished = pyqtSignal()
+
+    @pyqtProperty(bool, notify = hasErrorUpdated)
+    def hasError(self) -> bool:
+        return self._has_errors
+
+    @pyqtProperty(bool, notify = needToWaitForResultChanged)
+    def needToWaitForResult(self) -> bool:
+        return self._need_to_check or self._check_in_progress
+
+    # Starts the error check timer to schedule a new error check.
+    def startErrorCheck(self, *args):
+        if not self._check_in_progress:
+            self._need_to_check = True
+            self.needToWaitForResultChanged.emit()
+        self._error_check_timer.start()
+
+    # This function is called by the timer to reschedule a new error check.
+    # If there is no check in progress, it will start a new one. If there is any, it sets the "_need_to_check" flag
+    # to notify the current check to stop and start a new one.
+    def _rescheduleCheck(self):
+        if self._check_in_progress and not self._need_to_check:
+            self._need_to_check = True
+            self.needToWaitForResultChanged.emit()
+            return
+
+        self._error_keys_in_progress = set()
+        self._need_to_check = False
+        self.needToWaitForResultChanged.emit()
+
+        global_stack = self._machine_manager.activeMachine
+        if global_stack is None:
+            Logger.log("i", "No active machine, nothing to check.")
+            return
+
+        self._stacks_to_check = deque([global_stack] + list(global_stack.extruders.values()))
+        self._keys_to_check = deque(global_stack.getAllKeys())
+
+        self._application.callLater(self._checkStack)
+        Logger.log("d", "New error check scheduled.")
+
+    def _checkStack(self):
+        from UM.Settings.SettingDefinition import SettingDefinition
+        from UM.Settings.Validator import ValidatorState
+
+        if self._need_to_check:
+            Logger.log("d", "Need to check for errors again. Discard the current progress and reschedule a check.")
+            self._check_in_progress = False
+            self._application.callLater(self.startErrorCheck)
+            return
+
+        self._check_in_progress = True
+
+        # If there is nothing to check any more, it means there is no error.
+        if not self._stacks_to_check or not self._keys_to_check:
+            # Finish
+            self._setResult(False)
+            return
+
+        stack = self._stacks_to_check[0]
+        key = self._keys_to_check.popleft()
+
+        # If there is no key left in this stack, check the next stack later.
+        if not self._keys_to_check:
+            if len(self._stacks_to_check) == 1:
+                stacks = None
+                keys = None
+            else:
+                stack = self._stacks_to_check.popleft()
+                self._keys_to_check = deque(stack.getAllKeys())
+
+        enabled = stack.getProperty(key, "enabled")
+        if not enabled:
+            self._application.callLater(self._checkStack)
+            return
+
+        validation_state = stack.getProperty(key, "validationState")
+        if validation_state is None:
+            # Setting is not validated. This can happen if there is only a setting definition.
+            # We do need to validate it, because a setting definitions value can be set by a function, which could
+            # be an invalid setting.
+            definition = stack.getSettingDefinition(key)
+            validator_type = SettingDefinition.getValidatorForType(definition.type)
+            if validator_type:
+                validator = validator_type(key)
+                validation_state = validator(stack)
+        if validation_state in (ValidatorState.Exception, ValidatorState.MaximumError, ValidatorState.MinimumError):
+            # Finish
+            self._setResult(True)
+            return
+
+        # Schedule the check for the next key
+        self._application.callLater(self._checkStack)
+
+    def _setResult(self, result: bool):
+        if result != self._has_errors:
+            self._has_errors = result
+            self.hasErrorUpdated.emit()
+            self._machine_manager.stacksValidationChanged.emit()
+        self._need_to_check = False
+        self._check_in_progress = False
+        self.needToWaitForResultChanged.emit()
+        self.errorCheckFinished.emit()
+        Logger.log("i", "Error check finished, result = %s", result)