Set the window modality just before the window is shown on Wx.

This prevents exceptions raised during initialization from blocking the
rest of the app, since Wx blocks as soon as the flag is set, instead of
when the window becomes visible.

enaml/wx/wx_window.py

@@ -139,8 +139,6 @@ def init_widget(self):
             self.set_title(d.title)
         if -1 not in d.initial_size:
             self.set_initial_size(d.initial_size)
-        if d.modality != 'non_modal':
-            self.set_modality(d.modality)
         if d.icon:
             self.set_icon(d.icon)
         self.widget.Bind(wx.EVT_CLOSE, self.on_close)
@@ -274,3 +272,35 @@ def set_modality(self, modality):
             self.widget.MakeModal(False)
         else:
             self.widget.MakeModal(True)
+
+    #--------------------------------------------------------------------------
+    # Overrides
+    #--------------------------------------------------------------------------
+    def set_visible(self, visible):
+        """ Set the visibility state on the underlying widget.
+
+        This override sets the modality to false when hiding the window
+        and enabled it when showing the window (if requested).
+
+        """
+        modality = self.declaration.modality
+        self.widget.MakeModal(visible and modality != 'non_modal')
+        self.widget.Show(visible)
+
+    def ensure_visible(self):
+        """ Ensure the widget is visible.
+
+        This override forwards to the 'set_visible' method so that the
+        window modality is handled properly.
+
+        """
+        self.set_visible(True)
+
+    def ensure_hidden(self):
+        """ Ensure the widget is hidden.
+
+        This override forwards to the 'set_visible' method so that the
+        window modality is handled properly.
+
+        """
+        self.set_visible(False)