Thanks Roger, I think I understand now how it works internally. Below is a long suggestion for behavior, but please feel free to ignore Since CoolTerm is already a great tool as is.
Also, shouldn't 'unchanged' in the link below be 'changed' ? I may be missing something.
https://i.imgur.com/LPuEiKB.png
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I think that the use of CoolTerm fall into two modes, 'document centric' and 'independent'. In the document centric mode the user is aware and uses of the named .stc documents, e.g. by opening/saving/managing them. In the 'indepedent' mode the user just launch CoolTerm and uses and save the defaults without explicitly using named .stc documents.
The current behavior is intuitive for the 'document centric' mode and less for the independent mode. I would suggest not to introduce the document name (e.g. untitled_0) until the user opened a document or saved a document. Something along these lines
1. User open CoolTerm. Default are loaded and document name is not displayed.
2. User modifies parameters. Document name is still not displayed.
3. One of these happens:
A. If user try to close, the warning pops ups, and if the user saves the options as to a named file name that name is displayed at the top.
B. User saves the the defaults. File name is still not shown and all changes are considered saved.
C. User tries to exit and get the unsaved changes warning.
I think the change here is that CoolTerm has the notion (and name) of a file, only when the user performed a file operation (open, save, save_as).