Selecting initial characters and pressing . or invalid character for the filter inserts wrong charaters at FilteredLineEdit and FilteredTextEdit

[acgc99]

Bugs at FilteredLineEdit and FilteredTextEdit:

• In +0f mode. Example onFilteredLineEdit: 42, select 4, press ., makes text = .2.
• In f mode. Example onFilteredLineEdit: 42, select 4, press ., makes text = 222.
• In +0f or f mode. Example onFilteredLineEdit: 42, select 4, press invalid character by the filter, makes text = 222.

The desired behaviour would be:

• If .: replace selected text by 0..
• If invalid character by filter: delete selected text.
• Check also caret position if you are facing this issue.

I think this is hard (or impossible) to solve because:

• When _on_text_changed is called, the selection is already lost, so it cannot be known what was selected.
• If you try to compare old_text and new_text and selection only applies to one character, you cannot distinguish between that selection or a simple deletion of one character.
• get_selection_from_column and get_selection_to_column return -1 (error), so they cannot be used either.

If this is not solved, the user can set FilteredLineEdit.selecting_enabled = false and FilteredTextEdit.selecting_enabled = false. This have also disadvantages, you can't select text and copy it, you would have to implement some button.