For an empty partition.

Author: Zerline

sage_combinat_widgets/grid_view_editor.py

@@ -228,7 +228,7 @@ def compute(self, obj=None):
         """
         if not obj:
             obj = self.value
-        if not obj:
+        if obj is None:
             return
         self.cells = self.adapter.compute_cells(obj)
         celltype = self.adapter.celltype
@@ -290,7 +290,10 @@ def compute_height(self):
         """
         if not hasattr(self, 'cells'):
             self.compute()
-        maxpos = max(pos[0] for pos in self.cells)
+        if self.cells:
+            maxpos = max(pos[0] for pos in self.cells)
+        else:
+            maxpos = -1
         self.height = maxpos + 1 # Number of rows in self.value
         for pos in self.addable_cells():
             if pos[0] > maxpos:
@@ -709,6 +712,11 @@ def remove_cell(self, change):
             sage: e.remove_cell(Bunch({'name': 'cell_0_4', 'old': 3, 'new': 0, 'owner': e, 'type': 'change'}))
             sage: e.value
             [[None, None, 1, 2], [None, 1], [4]]
+            sage: p = Partition([1])
+            sage: e = GridViewEditor(p)
+            sage: e.remove_cell(Bunch({'name': 'cell_0_0', 'old': False, 'new': True, 'owner': e, 'type': 'change'}))
+            sage: e.value
+            []
         """
         # Do nothing at widget donottrack and do not track widget value
         if self.donottrack or change.name == 'value':

sage_combinat_widgets/grid_view_widget.py

@@ -504,6 +504,7 @@ def draw(self, cell_widget_classes=None, cell_widget_class_index=None,
             addable_widget_class = self.addable_widget_class
         if not blank_widget_class:
             blank_widget_class = self.blank_widget_class
+        i, j = -1, -1 # initialization ; necessary for an empty grid
         for i in range(self.height):
             r = rows[i]
             if not r: # Empty row