DomainEditor: Use signals instead of calling open_context on widget

Orange/widgets/data/owfile.py

@@ -269,6 +269,7 @@ def load_data(self):
         # We need to catch any exception type since anything can happen in
         # file readers
         # pylint: disable=broad-except
+        self.closeContext()
         self.domain_editor.set_domain(None)
         self.apply_button.setEnabled(False)
         self.Warning.file_too_big.clear()
@@ -306,7 +307,7 @@ def load_data(self):
 
         add_origin(data, self.loaded_file or self.last_path())
         self.data = data
-        self.domain_editor.set_domain(data.domain)
+        self.openContext(data.domain)
         self.apply_domain_edit()  # sends data
 
     def _get_reader(self):

Orange/widgets/utils/domaineditor.py

@@ -167,8 +167,8 @@ class DomainEditor(QTableView):
     def __init__(self, widget):
         super().__init__()
         widget.settingsHandler.initialize(self)
-        self.openContext = widget.openContext
-        self.closeContext = widget.closeContext
+        widget.contextAboutToBeOpened.connect(lambda args: self.set_domain(args[0]))
+        widget.contextOpened.connect(self.update_model)
 
         self.setModel(VarTableModel(self.variables))
         self.setSelectionMode(QTableView.NoSelection)
@@ -238,18 +238,9 @@ def is_missing(x):
         return domain, cols
 
     def set_domain(self, domain):
-        """Update the widget with information about given domain.
-
-        If domain has been seen before (saved context settings),
-        the existing edits will be shown.
-
-        Parameters
-        ----------
-        domain : of the new data file.
-        """
-        self.closeContext()
         self.variables = self.parse_domain(domain)
-        self.openContext(domain)
+
+    def update_model(self):
         self.model().set_variables(self.variables)
 
     @staticmethod

Orange/widgets/widget.py

@@ -7,8 +7,7 @@
     QShortcut, QSplitter, QSplitterHandle, QPushButton
 )
 from AnyQt.QtCore import (
-    Qt, QByteArray, QSettings, QUrl, pyqtSignal as Signal
-)
+    Qt, QByteArray, QSettings, QUrl, pyqtSignal as Signal)
 from AnyQt.QtGui import QIcon, QKeySequence, QDesktopServices
 
 from Orange.data import FileFormat
@@ -172,6 +171,9 @@ class OWWidget(QDialog, OWComponent, Report, ProgressBarMixin,
     #: :type: list of :class:`Message`
     UserAdviceMessages = []
 
+    contextAboutToBeOpened = Signal(object)
+    contextOpened = Signal()
+
     def __new__(cls, *args, captionTitle=None, **kwargs):
         self = super().__new__(cls, None, cls.get_flags())
         QDialog.__init__(self, None, self.get_flags())
@@ -488,7 +490,9 @@ def openContext(self, *a):
         `DomainContextHandler` expects `Orange.data.Table` or
         `Orange.data.Domain`.
         """
+        self.contextAboutToBeOpened.emit(a)
         self.settingsHandler.open_context(self, *a)
+        self.contextOpened.emit()
 
     def closeContext(self):
         """Save the current settings and close the current context.