Start page: use ipw.VBox instead of ipw.Output to display apps (#185

)

Also, remove the decorator used as a workaround.

home/start_page.py

@@ -1,15 +1,13 @@
 """Module to generate AiiDAlab home page."""
 
 import json
-from functools import wraps
 from glob import glob
 from os import path
 
 import ipywidgets as ipw
 import traitlets
 from aiidalab.app import AiidaLabApp
 from aiidalab.config import AIIDALAB_APPS
-from IPython.display import display
 
 from home.utils import load_widget
 from home.widgets import AppStatusInfoWidget
@@ -30,37 +28,12 @@ def create_app_widget_move_buttons(name):
     return app_widget_move_buttons
 
 
-def _workaround_property_lock_issue(func):
-    """Work-around for issue with the ipw.Accordion widget.
-
-    The widget does not report changes to the .selected_index trait when displayed
-    within a custom ipw.Output instance. However, the change is somewhat cryptic reported
-    by a change to the private '_property_lock' trait. We observe changes to that trait
-    and convert the change argument into a form that is more like the one expected by
-    downstream handlers.
-    """
-
-    @wraps(func)
-    def _inner(self, change):
-        if change["name"] == "_property_lock":
-            if "selected_index" in change["old"]:
-                fixed_change = change.copy()
-                fixed_change["name"] = "selected_index"
-                fixed_change["new"] = change["old"]["selected_index"]
-                del fixed_change["old"]
-                return func(self, fixed_change)
-
-        return func(self, change)
-
-    return _inner
-
-
 class AiidaLabHome:
     """Class that mananges the appearance of the AiiDAlab home page."""
 
     def __init__(self):
         self.config_fn = ".launcher.json"
-        self.output = ipw.Output()
+        self.output = ipw.VBox()
         self._app_widgets = {}
 
     def _create_app_widget(self, name):
@@ -98,17 +71,17 @@ def read_config(self):
 
     def render(self):
         """Rendering all apps."""
-        self.output.clear_output()
-        apps = self.load_apps()
 
-        with self.output:
-            for name in apps:
-                # Create app widget if it has not been created yet.
-                if name not in self._app_widgets:
-                    self._app_widgets[name] = self._create_app_widget(name)
+        displayed_apps = []
+        apps = self.load_apps()
 
-                display(self._app_widgets[name])
+        for name in apps:
+            # Create app widget if it has not been created yet.
+            if name not in self._app_widgets:
+                self._app_widgets[name] = self._create_app_widget(name)
 
+            displayed_apps.append(self._app_widgets[name])
+        self.output.children = displayed_apps
         return self.output
 
     def load_apps(self):
@@ -186,24 +159,17 @@ def __init__(self, app, allow_move=False, allow_manage=True):
 class CollapsableAppWidget(ipw.Accordion):
     """Widget that represents a collapsable app as part of the home page."""
 
-    hidden = traitlets.Bool()
+    hidden = traitlets.Bool(None, allow_none=True)
 
     def __init__(self, app, **kwargs):
         self.app = app
         app_widget = AppWidget(app, **kwargs)
         super().__init__(children=[app_widget])
         self.set_title(0, app.title)
-        # Need to observe all names here due to unidentified issue:
-        self.observe(
-            self._observe_accordion_selected_index
-        )  # , names=['selected_index'])
 
-    @_workaround_property_lock_issue
+    @traitlets.observe("selected_index")
     def _observe_accordion_selected_index(self, change):
-        if (
-            change["name"] == "selected_index"
-        ):  # Observing all names due to unidentified issue.
-            self.hidden = change["new"] is None
+        self.hidden = change["new"] is None
 
     @traitlets.observe("hidden")
     def _observe_hidden(self, change):