[Qgis-developer] Disable undo feature for user geometry edits within plugin / general undoStack() questions

[John Stevenson]

Hi,

I am writing a plugin that modifies a spatialite database in response to geometry edits made by the user.  The attribute table for the modified feature is modified when an item is added or edited, and additional tables within the database are updated with the new information.  The undo button does not revert the database changes (and can cause crashed in Linux), so I would like to prevent the user being able to use it.

So far, I have worked out how to disable the undo button (and shortcut) by disabling the corresponding action.  But when I connect that to a signal, it fires but the undo is still enabled, but with a different corresponding action.

So far I have a class that initiates on beginEditing whose contents include the following:

```
def __init__(self, iface, layer, db):
    ..... various lines here ....
    self.undo_stack = layer.undoStack()

def connect_signals(self):
    ....various lines here....
    self.undo_stack.indexChanged.connect(self.disable_undo_button)
    self.undo_stack.canUndoChanged.connect(self.disable_undo_button)
    self.undo_stack.cleanChanged.connect(self.disable_undo_button)
    self.undo_stack.undoTextChanged.connect(self.disable_undo_button)

def disable_undo_button(self):
    """
   Disable GUI undo buttons to prevent user trying to undo edits, which
    is prone to causing crashes.
    """
    print('Disabling undo button')
    actions_to_disable = ['&Undo', '&Redo']
    for action in self.iface.editMenu().actions():
        menu_item_action_text = action.text()
        if menu_item_action_text in actions_to_disable:
            action.setDisabled(True)
            print(id(action))
```

The disable_undo_button() function works, so it seems that another action is being added as the current undo without any of the signals that I am listening for being called.

- When is the final change made to the undoStack?
- Is there a signal that I can listen for to disable undo afterwards?
- or is there generally a better way to disable undo functionality?

Cheers
John


John Stevenson
Senior Developer


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