Experiment: Add a GUI-providing plugin

envisage/examples/demo/GUI_Application/traitsui_gui_app.py

@@ -10,11 +10,12 @@
 
 """ A simple example of a GUIApplication which wraps a TraitsUI """
 
+from pyface.api import SplashScreen
 from traits.api import Enum, HasTraits, Instance, Int, on_trait_change, Str
-from traitsui.api import Item, OKCancelButtons, View
+from traitsui.api import Item, View
 
-from envisage.api import Plugin
-from envisage.ui.gui_application import GUIApplication
+from envisage.api import CorePlugin, Plugin
+from envisage.ui.api import GUIApplication, GUIPlugin
 
 
 class Person(HasTraits):
@@ -30,7 +31,6 @@ class Person(HasTraits):
         Item("name"),
         Item("age"),
         Item("gender"),
-        buttons=OKCancelButtons,
     )
 
 
@@ -51,15 +51,27 @@ def on_application_start(self):
         person = Person()
 
         # keep a reference to the ui object to avoid garbage collection
-        self.ui = person.edit_traits()
+        self.ui = person.edit_traits(kind="live")
 
 
-# Application entry point.
-if __name__ == "__main__":
+def main():
+    """Main method of the traitsui gui app example"""
+
     # Create the application.
     application = GUIApplication(
-        id="person_view", plugins=[PersonViewPlugin()]
+        id="person_view",
+        plugins=[
+            CorePlugin(),
+            GUIPlugin(),
+            PersonViewPlugin(),
+        ],
+        splash_screen=SplashScreen(image="splash"),
     )
 
     # Run it!
     application.run()
+
+
+# Application entry point.
+if __name__ == "__main__":
+    main()

envisage/examples/demo/plugins/tasks/run_attractor.py

@@ -10,6 +10,7 @@
 
 # Plugin imports.
 from envisage.api import CorePlugin
+from envisage.ui.api import GUIPlugin
 from envisage.ui.tasks.api import TasksPlugin
 
 
@@ -20,7 +21,7 @@ def main(argv):
     from attractors.attractors_application import AttractorsApplication
     from attractors.attractors_plugin import AttractorsPlugin
 
-    plugins = [CorePlugin(), TasksPlugin(), AttractorsPlugin()]
+    plugins = [CorePlugin(), GUIPlugin(), TasksPlugin(), AttractorsPlugin()]
     app = AttractorsApplication(plugins=plugins)
     app.run()
 

envisage/ui/api.py

@@ -0,0 +1,17 @@
+# (C) Copyright 2007-2023 Enthought, Inc., Austin, TX
+# All rights reserved.
+#
+# This software is provided without warranty under the terms of the BSD
+# license included in LICENSE.txt and may be redistributed only under
+# the conditions described in the aforementioned license. The license
+# is also available online at http://www.enthought.com/licenses/BSD.txt
+#
+# Thanks for using Enthought open source!
+"""
+- :class:`~.IGUI_PROTOCOL`
+- :class:`~.GUIApplication`
+- :class:`~.GUIPlugin`
+"""
+from .gui_application import GUIApplication
+from .gui_plugin import GUIPlugin
+from .ids import IGUI_PROTOCOL

envisage/ui/gui_application.py

@@ -21,9 +21,10 @@
 
 """
 
-from traits.api import Event, Supports
+from traits.api import Event, Instance, observe
 
 from envisage.api import Application
+from envisage.ui.ids import IGUI_PROTOCOL
 
 
 class GUIApplication(Application):
@@ -42,11 +43,11 @@ class GUIApplication(Application):
     #### 'GUIApplication' interface #########################################
 
     #: The Pyface GUI for the application.
-    gui = Supports("pyface.i_gui.IGUI")
+    gui = Instance(IGUI_PROTOCOL)
 
     #: The splash screen for the application. By default, there is no splash
     #: screen.
-    splash_screen = Supports("pyface.i_splash_screen.ISplashScreen")
+    splash_screen = Instance("pyface.i_splash_screen.ISplashScreen")
 
     #### Application lifecycle events #########################################
 
@@ -67,25 +68,41 @@ def run(self):
             veto).
 
         """
-
-        # Make sure the GUI has been created (so that, if required, the splash
-        # screen is shown).
-        gui = self.gui
+        # show the splash screen if provided
+        if self.splash_screen is not None:
+            self.splash_screen.open()
 
         started = self.start()
         if started:
-            gui.set_trait_later(self, "application_initialized", self)
+            if self.gui is None:
+                gui_services = self.get_services(IGUI_PROTOCOL)
+                if gui_services:
+                    self.gui = gui_services[0]
+                else:
+                    # fall-back if not provided by plugin
+                    from pyface.api import GUI
+
+                    self.gui = GUI()
+            self.gui.set_trait_later(self, "application_initialized", self)
+
             # Start the GUI event loop.  The application will block here.
-            gui.start_event_loop()
+            self.gui.start_event_loop()
+
+            self.gui = None
 
             # clean up plugins once event loop stops
             self.stop()
 
         return started
 
-    #### Trait initializers ###################################################
+    #### Trait observers ######################################################
 
-    def _gui_default(self):
-        from pyface.api import GUI
-
-        return GUI(splash_screen=self.splash_screen)
+    @observe("application_initialized")
+    def _close_splash_screen(self, event):
+        """
+        Once the app has started we don't need the splash screen any more.
+        """
+        if self.splash_screen is not None:
+            self.splash_screen.close()
+            self.splash_screen.destroy()
+            self.splash_screen = None

envisage/ui/gui_plugin.py

@@ -0,0 +1,88 @@
+# (C) Copyright 2007-2023 Enthought, Inc., Austin, TX
+# All rights reserved.
+#
+# This software is provided without warranty under the terms of the BSD
+# license included in LICENSE.txt and may be redistributed only under
+# the conditions described in the aforementioned license. The license
+# is also available online at http://www.enthought.com/licenses/BSD.txt
+#
+# Thanks for using Enthought open source!
+"""
+Envisage GUI Plugin
+-------------------
+
+This is a plugin which contributes a Pyface GUI instance to be used in
+applications with a desktop UI.  This does not support the splash screen
+features of IGUI - those are better controlled by the application or main
+script as they generally should be shown as soon as possible after startup,
+often before expensive imports or operations.
+"""
+
+from traits.api import Instance, List
+
+from envisage.ids import SERVICE_OFFERS
+from envisage.plugin import Plugin
+from envisage.service_offer import ServiceOffer
+from envisage.ui.ids import IGUI_PROTOCOL
+
+
+class GUIPlugin(Plugin):
+    """A simple plugin that provides a Pyface GUI.
+
+    This class handles the life-cycle of a Pyface GUI.  Applications that need
+    the GUI object should request the `pyface.i_gui.IGUI` interface, allowing
+    things like alternative event loops (eg. intergation with asyncio).
+    """
+
+    #### 'GUIPlugin' interface #########################################
+
+    service_offers = List(contributes_to=SERVICE_OFFERS)
+
+    #: The Pyface GUI for the application.
+    _gui = Instance("pyface.i_gui.IGUI")
+
+    #### 'IPlugin' interface ##################################################
+
+    #: The plugin's unique identifier.
+    id = "envisage.ui.gui"
+
+    #: The plugin's name (suitable for displaying to the user).
+    name = "GUI Plugin"
+
+    ###########################################################################
+    # 'IPlugin' interface.
+    ###########################################################################
+
+    def stop(self):
+        self._destroy_gui()
+        super().stop()
+
+    ###########################################################################
+    # Private interface.
+    ###########################################################################
+
+    def _create_gui(self):
+        if self._gui is None:
+            from pyface.gui import GUI
+
+            self._gui = GUI()
+
+        return self._gui
+
+    def _destroy_gui(self):
+        if self._gui is not None:
+            self._gui = None
+
+    #### Trait initializers ###################################################
+
+    def _service_offers_default(self):
+        i_gui_service_offer = ServiceOffer(
+            protocol=IGUI_PROTOCOL,
+            factory=self._create_gui,
+        )
+        return [i_gui_service_offer]
+
+    def __gui_default(self):
+        from pyface.gui import GUI
+
+        return GUI()

envisage/ui/ids.py

@@ -0,0 +1,12 @@
+# (C) Copyright 2007-2023 Enthought, Inc., Austin, TX
+# All rights reserved.
+#
+# This software is provided without warranty under the terms of the BSD
+# license included in LICENSE.txt and may be redistributed only under
+# the conditions described in the aforementioned license. The license
+# is also available online at http://www.enthought.com/licenses/BSD.txt
+#
+# Thanks for using Enthought open source!
+
+#: IGUI service protocol
+IGUI_PROTOCOL = "pyface.i_gui.IGUI"

envisage/ui/tasks/tasks_application.py

@@ -21,13 +21,15 @@
     Instance,
     Int,
     List,
+    observe,
     Str,
     Vetoable,
 )
 from traits.etsconfig.api import ETSConfig
 
 # Enthought library imports.
-from envisage.api import Application, ExtensionPoint
+from envisage.api import ExtensionPoint
+from envisage.ui.api import GUIApplication
 
 # Logging.
 logger = logging.getLogger(__name__)
@@ -36,7 +38,7 @@
 DEFAULT_STATE_FILENAME = "application_memento"
 
 
-class TasksApplication(Application):
+class TasksApplication(GUIApplication):
     """The entry point for an Envisage Tasks application.
 
     This class handles the common case for Tasks applications and is
@@ -58,20 +60,13 @@ class TasksApplication(Application):
     #: The active task window (the last one to get focus).
     active_window = Instance("envisage.ui.tasks.task_window.TaskWindow")
 
-    #: The Pyface GUI for the application.
-    gui = Instance("pyface.i_gui.IGUI")
-
     #: Icon for the whole application. Will be used to override all taskWindows
     #: icons to have the same.
     icon = Instance("pyface.image_resource.ImageResource", allow_none=True)
 
     #: The name of the application (also used on window title bars).
     name = Str
 
-    #: The splash screen for the application. By default, there is no splash
-    #: screen.
-    splash_screen = Instance("pyface.splash_screen.SplashScreen")
-
     #: The directory on the local file system used to persist window layout
     #: information.
     state_location = Directory
@@ -152,35 +147,6 @@ class TasksApplication(Application):
         "envisage.ui.tasks.tasks_application.TasksApplicationState"
     )
 
-    ###########################################################################
-    # 'IApplication' interface.
-    ###########################################################################
-
-    def run(self):
-        """Run the application.
-
-        Returns
-        -------
-        bool
-            Whether the application started successfully (i.e., without a
-            veto).
-        """
-        # Make sure the GUI has been created (so that, if required, the splash
-        # screen is shown).
-        gui = self.gui
-
-        started = self.start()
-        if started:
-            # Create windows from the default or saved application layout.
-            self._create_windows()
-
-            # Start the GUI event loop.
-            gui.set_trait_later(self, "application_initialized", self)
-            gui.start_event_loop()
-            self.stop()
-
-        return started
-
     ###########################################################################
     # 'TasksApplication' interface.
     ###########################################################################
@@ -462,11 +428,6 @@ def _default_layout_default(self):
             window_layout.items = [self.task_factories[0].id]
         return [window_layout]
 
-    def _gui_default(self):
-        from pyface.gui import GUI
-
-        return GUI(splash_screen=self.splash_screen)
-
     def _state_location_default(self):
         state_location = os.path.join(self.home, "tasks", ETSConfig.toolkit)
         logger.debug("Tasks state location is %s", state_location)
@@ -475,6 +436,10 @@ def _state_location_default(self):
 
     #### Trait change handlers ################################################
 
+    @observe("application_initialized")
+    def _show_initial_windows(self, event):
+        self._create_windows()
+
     def _on_window_activated(self, window, trait_name, event):
         self.active_window = window
 

envisage/ui/tasks/tasks_plugin.py

@@ -7,6 +7,7 @@
 # is also available online at http://www.enthought.com/licenses/BSD.txt
 #
 # Thanks for using Enthought open source!
+
 # Enthought library imports.
 from traits.api import Callable, Instance, List