Enable/disable Apply button depending on valid context selection

avalon/tools/contextmanager/app.py

@@ -77,12 +77,16 @@ def __init__(self, parent=None):
         self._task_view = task_view
         self._task_model = task_model
         self._assets = assets
+        self._accept_button = accept_btn
 
         self._context_asset = asset_label
         self._context_task = task_label
 
         assets.selection_changed.connect(self.on_asset_changed)
         accept_btn.clicked.connect(self.on_accept_clicked)
+        task_view.selectionModel().selectionChanged.connect(
+            self.on_task_changed)
+        assets.assets_refreshed.connect(self.on_task_changed)
         assets.refresh()
 
         self.select_asset(api.Session["AVALON_ASSET"])
@@ -140,6 +144,23 @@ def on_asset_changed(self):
         if self._last_selected_task:
             self.select_task(self._last_selected_task)
 
+        if not self._get_selected_task_name():
+            # If no task got selected after the task model reset
+            # then a "selection change" signal is not emitted.
+            # As such we need to explicitly force the callback.
+            self.on_task_changed()
+
+    def on_task_changed(self):
+        """Callback on task change."""
+
+        # Toggle the "Accept" button enabled state
+        asset = self._get_selected_asset_name()
+        task = self._get_selected_task_name()
+        if not asset or not task:
+            self._accept_button.setEnabled(False)
+        else:
+            self._accept_button.setEnabled(True)
+
     def on_accept_clicked(self):
         """Apply the currently selected task to update current task"""