PR: Improve UI of PaneEmptyWidget, show message on panes connected to dead consoles and improve About dialog UI

spyder/api/shellconnect/main_widget.py

@@ -15,6 +15,7 @@
 # Local imports
 from spyder.api.translations import _
 from spyder.api.widgets.main_widget import PluginMainWidget
+from spyder.widgets.helperwidgets import PaneEmptyWidget
 
 
 class ShellConnectMainWidget(PluginMainWidget):
@@ -40,6 +41,24 @@ def __init__(self, *args, **kwargs):
         layout.addWidget(self._stack)
         self.setLayout(layout)
 
+    # ---- PluginMainWidget API
+    # ------------------------------------------------------------------------
+    def current_widget(self):
+        """
+        Return the current widget in the stack.
+
+        Returns
+        -------
+        QWidget
+            The current widget.
+        """
+        return self._stack.currentWidget()
+
+    def get_focus_widget(self):
+        return self.current_widget()
+
+    # ---- SpyderWidgetMixin API
+    # ------------------------------------------------------------------------
     def update_style(self):
         self._stack.setStyleSheet("QStackedWidget {padding: 0px; border: 0px}")
 
@@ -56,20 +75,6 @@ def count(self):
         """
         return self._stack.count()
 
-    def current_widget(self):
-        """
-        Return the current figure browser widget in the stack.
-
-        Returns
-        -------
-        QWidget
-            The current widget.
-        """
-        return self._stack.currentWidget()
-
-    def get_focus_widget(self):
-        return self.current_widget()
-
     def get_widget_for_shellwidget(self, shellwidget):
         """return widget corresponding to shellwidget."""
         shellwidget_id = id(shellwidget)
@@ -80,10 +85,7 @@ def get_widget_for_shellwidget(self, shellwidget):
     # ---- Public API
     # ------------------------------------------------------------------------
     def add_shellwidget(self, shellwidget):
-        """
-        Create a new widget in the stack and associate it to
-        shellwidget.
-        """
+        """Create a new widget in the stack and associate it to shellwidget."""
         shellwidget_id = id(shellwidget)
         if shellwidget_id not in self._shellwidgets:
             widget = self.create_new_widget(shellwidget)
@@ -109,17 +111,38 @@ def remove_shellwidget(self, shellwidget):
             self.update_actions()
 
     def set_shellwidget(self, shellwidget):
-        """
-        Set widget associated with shellwidget as the current widget.
-        """
+        """Set widget associated with shellwidget as the current widget."""
         old_widget = self.current_widget()
         widget = self.get_widget_for_shellwidget(shellwidget)
         if widget is None:
             return
+
         self._stack.setCurrentWidget(widget)
         self.switch_widget(widget, old_widget)
         self.update_actions()
 
+    def add_errored_shellwidget(self, shellwidget):
+        """
+        Create a new PaneEmptyWidget in the stack and associate it to
+        shellwidget.
+
+        This is necessary to show a meaningful message when switching to
+        consoles with dead kernels.
+        """
+        shellwidget_id = id(shellwidget)
+        if shellwidget_id not in self._shellwidgets:
+            widget = PaneEmptyWidget(
+                self,
+                "variable-explorer",  # TODO: Use custom icon here
+                _("No connected console"),
+                _("The current console failed to start, so there is no "
+                  "content to show here.")
+            )
+
+            self._stack.addWidget(widget)
+            self._shellwidgets[shellwidget_id] = widget
+            self.set_shellwidget(shellwidget)
+
     def create_new_widget(self, shellwidget):
         """Create a widget to communicate with shellwidget."""
         raise NotImplementedError
@@ -137,3 +160,7 @@ def refresh(self):
         if self.count():
             widget = self.current_widget()
             widget.refresh()
+
+    def is_current_widget_empty(self):
+        """Check if the current widget is a PaneEmptyWidget."""
+        return isinstance(self.current_widget(), PaneEmptyWidget)

spyder/api/shellconnect/mixins.py

@@ -15,11 +15,54 @@
 
 class ShellConnectMixin:
     """
-    Mixin to connect a plugin composed of stacked widgets to the shell
-    widgets in the IPython console.
+    Mixin to connect any widget or object to the shell widgets in the IPython
+    console.
+    """
+
+    # ---- Connection to the IPython console
+    # -------------------------------------------------------------------------
+    def register_ipythonconsole(self, ipyconsole):
+        """Register signals from the console."""
+        ipyconsole.sig_shellwidget_changed.connect(self.set_shellwidget)
+        ipyconsole.sig_shellwidget_created.connect(self.add_shellwidget)
+        ipyconsole.sig_shellwidget_deleted.connect(self.remove_shellwidget)
+        ipyconsole.sig_shellwidget_errored.connect(
+            self.add_errored_shellwidget)
+
+    def unregister_ipythonconsole(self, ipyconsole):
+        """Unregister signals from the console."""
+        ipyconsole.sig_shellwidget_changed.disconnect(self.set_shellwidget)
+        ipyconsole.sig_shellwidget_created.disconnect(self.add_shellwidget)
+        ipyconsole.sig_shellwidget_deleted.disconnect(self.remove_shellwidget)
+        ipyconsole.sig_shellwidget_errored.disconnect(
+            self.add_errored_shellwidget)
+
+    # ---- Public API
+    # -------------------------------------------------------------------------
+    def set_shellwidget(self, shellwidget):
+        """Update the current shellwidget."""
+        raise NotImplementedError
+
+    def add_shellwidget(self, shellwidget):
+        """Add a new shellwidget to be registered."""
+        raise NotImplementedError
+
+    def remove_shellwidget(self, shellwidget):
+        """Remove a registered shellwidget."""
+        raise NotImplementedError
+
+    def add_errored_shellwidget(self, shellwidget):
+        """Register a new shellwidget whose kernel failed to start."""
+        raise NotImplementedError
+
+
+class ShellConnectPluginMixin(ShellConnectMixin):
+    """
+    Mixin to connect a plugin composed of stacked widgets to the shell widgets
+    in the IPython console.
 
     It is assumed that self.get_widget() returns an instance of
-    ShellConnectMainWidget
+    ShellConnectMainWidget.
     """
 
     # ---- Connection to the IPython console
@@ -30,25 +73,12 @@ def on_ipython_console_available(self):
         ipyconsole = self.get_plugin(Plugins.IPythonConsole)
         self.register_ipythonconsole(ipyconsole)
 
-    def register_ipythonconsole(self, ipyconsole):
-        """Register the console."""
-        ipyconsole.sig_shellwidget_changed.connect(self.set_shellwidget)
-        ipyconsole.sig_shellwidget_created.connect(self.add_shellwidget)
-        ipyconsole.sig_shellwidget_deleted.connect(self.remove_shellwidget)
-
     @on_plugin_teardown(plugin=Plugins.IPythonConsole)
     def on_ipython_console_teardown(self):
         """Disconnect from the IPython console."""
         ipyconsole = self.get_plugin(Plugins.IPythonConsole)
         self.unregister_ipythonconsole(ipyconsole)
 
-    def unregister_ipythonconsole(self, ipyconsole):
-        """Unregister the console."""
-
-        ipyconsole.sig_shellwidget_changed.disconnect(self.set_shellwidget)
-        ipyconsole.sig_shellwidget_created.disconnect(self.add_shellwidget)
-        ipyconsole.sig_shellwidget_deleted.disconnect(self.remove_shellwidget)
-
     # ---- Public API
     # -------------------------------------------------------------------------
     def set_shellwidget(self, shellwidget):
@@ -78,7 +108,7 @@ def add_shellwidget(self, shellwidget):
 
     def remove_shellwidget(self, shellwidget):
         """
-        Remove the registered shellwidget.
+        Remove a registered shellwidget.
 
         Parameters
         ----------
@@ -87,6 +117,17 @@ def remove_shellwidget(self, shellwidget):
         """
         self.get_widget().remove_shellwidget(shellwidget)
 
+    def add_errored_shellwidget(self, shellwidget):
+        """
+        Add a new shellwidget whose kernel failed to start.
+
+        Parameters
+        ----------
+        shellwidget: spyder.plugins.ipyconsole.widgets.shell.ShellWidget
+            The shell widget.
+        """
+        self.get_widget().add_errored_shellwidget(shellwidget)
+
     def current_widget(self):
         """
         Return the current widget displayed at the moment.

spyder/api/utils.py

@@ -12,11 +12,9 @@
 
 def get_class_values(cls):
     """
-    Get the attribute values for the class enumerations used in our
-    API.
+    Get the attribute values for the class enumerations used in our API.
 
-    Idea from:
-    https://stackoverflow.com/a/17249228/438386
+    Idea from: https://stackoverflow.com/a/17249228/438386
     """
     return [v for (k, v) in cls.__dict__.items() if k[:1] != '_']
 
@@ -54,3 +52,15 @@ def __iter__(self):
             child = self.children[key]
             for prefix in child:
                 yield prefix
+
+
+class classproperty(property):
+    """
+    Decorator to declare class constants as properties that require additional
+    computation.
+
+    Taken from: https://stackoverflow.com/a/7864317/438386
+    """
+
+    def __get__(self, cls, owner):
+        return classmethod(self.fget).__get__(None, owner)()

spyder/app/mainwindow.py

@@ -666,11 +666,11 @@ def setup(self):
         logger.info("Applying theme configuration...")
         ui_theme = self.get_conf('ui_theme', section='appearance')
         color_scheme = self.get_conf('selected', section='appearance')
+        qapp = QApplication.instance()
 
         if ui_theme == 'dark':
             if not running_under_pytest():
                 # Set style proxy to fix combobox popup on mac and qdark
-                qapp = QApplication.instance()
                 qapp.setStyle(self._proxy_style)
             dark_qss = str(APP_STYLESHEET)
             self.setStyleSheet(dark_qss)
@@ -680,7 +680,6 @@ def setup(self):
         elif ui_theme == 'light':
             if not running_under_pytest():
                 # Set style proxy to fix combobox popup on mac and qdark
-                qapp = QApplication.instance()
                 qapp.setStyle(self._proxy_style)
             light_qss = str(APP_STYLESHEET)
             self.setStyleSheet(light_qss)
@@ -691,7 +690,6 @@ def setup(self):
             if not is_dark_font_color(color_scheme):
                 if not running_under_pytest():
                     # Set style proxy to fix combobox popup on mac and qdark
-                    qapp = QApplication.instance()
                     qapp.setStyle(self._proxy_style)
                 dark_qss = str(APP_STYLESHEET)
                 self.setStyleSheet(dark_qss)
@@ -703,6 +701,10 @@ def setup(self):
                 self.statusBar().setStyleSheet(light_qss)
                 css_path = CSS_PATH
 
+        # This needs to done after applying the stylesheet to the window
+        logger.info("Set color for links in Qt widgets")
+        set_links_color(qapp)
+
         # Set css_path as a configuration to be used by the plugins
         self.set_conf('css_path', css_path, section='appearance')
 
@@ -1439,9 +1441,6 @@ def main(options, args):
             pass
     CONF.set('main', 'previous_crash', previous_crash)
 
-    # **** Set color for links ****
-    set_links_color(app)
-
     # **** Create main window ****
     mainwindow = None
     try:

spyder/plugins/debugger/plugin.py

@@ -17,7 +17,7 @@
 from spyder.api.plugins import Plugins, SpyderDockablePlugin
 from spyder.api.plugin_registration.decorators import (
     on_plugin_available, on_plugin_teardown)
-from spyder.api.shellconnect.mixins import ShellConnectMixin
+from spyder.api.shellconnect.mixins import ShellConnectPluginMixin
 from spyder.api.translations import _
 from spyder.config.manager import CONF
 from spyder.plugins.debugger.confpage import DebuggerConfigPage
@@ -37,7 +37,7 @@
 from spyder.plugins.editor.api.run import CellRun, SelectionRun
 
 
-class Debugger(SpyderDockablePlugin, ShellConnectMixin, RunExecutor):
+class Debugger(SpyderDockablePlugin, ShellConnectPluginMixin, RunExecutor):
     """Debugger plugin."""
 
     NAME = 'debugger'