Added hscommon repo as a subtree

hscommon/gui/base.py

@@ -0,0 +1,58 @@
+# Created By: Virgil Dupras
+# Created On: 2011/09/09
+# Copyright 2013 Hardcoded Software (http://www.hardcoded.net)
+# 
+# This software is licensed under the "BSD" License as described in the "LICENSE" file, 
+# which should be included with this package. The terms are also available at 
+# http://www.hardcoded.net/licenses/bsd_license
+
+def noop(*args, **kwargs):
+    pass
+
+class NoopGUI:
+    def __getattr__(self, func_name):
+        return noop
+
+# A GUIObject is a cross-toolkit "model" representation of a GUI layer object, for example, a table.
+# It acts as a cross-toolkit interface to multiple what we call here a "view". That view is a
+# toolkit-specific controller to the actual view (an NSTableView, a QTableView, etc.).
+# In our GUIObject, we need a reference to that toolkit-specific controller because some actions,
+# have effects on it (for example, prompting it to refresh its data). The GUIObject is typically
+# instantiated before its "view", that is why we set it as None on init. However, the GUI
+# layer is supposed to set the view as soon as its toolkit-specific controller is instantiated.
+
+# When you subclass GUIObject, you will likely want to update its view on instantiation. That
+# is why we call self.view.refresh() in _view_updated(). If you need another type of action on
+# view instantiation, just override the method.
+class GUIObject:
+    def __init__(self):
+        self._view = None
+    
+    def _view_updated(self):
+        pass #virtual
+    
+    def has_view(self):
+        return (self._view is not None) and (not isinstance(self._view, NoopGUI))
+    
+    @property
+    def view(self):
+        return self._view
+    
+    @view.setter
+    def view(self, value):
+        # There's two times at which we set the view property: On initialization, where we set the
+        # view that we'll use for your lifetime, and just before the view is deallocated. We need
+        # to unset our view at that time to avoid calls to a deallocated instance (which means a
+        # crash).
+        if self._view is None:
+            # Initial view assignment
+            if value is None:
+                return 
+            self._view = value
+            self._view_updated()
+        else:
+            assert value is None
+            # Instead of None, we put a NoopGUI() there to avoid rogue view callback raising an
+            # exception.
+            self._view = NoopGUI()
+