Is it possible for a TreeModel to tell a CellRendererToggle that it is in an “in between” (inconsistent) state?
The gtk.CellRendererToggle has an “inconsistent” property, similar to the “active” property. If it is set to True, then the cell will display in the inconsistent state. You can either have a column in your model that maps to the inconsistent property, or use a cell data function to set the property based on some other condition. The C documentation lists all the CellRendererToggle’s properties: [developer.gnome.