Ctrl-S keyboard shortcut is silently ignored when editing a read-only file

When a read-only file is opened in Mousepad and modified in Mousepad, the Ctrl-S keyboard shortcut is being silently ignored.

Suggested solution: When Ctrl-S is pressed, display a popup window that informs the user that the opened file is read-only and that it cannot be saved.
When closing Mousepad and the read-only file has been internally modified in Mousepad, the displayed warning window (see the screenshot below) contains "Save As" instead of "Save" without providing a clue as to why the window contains "Save As" instead of "Save".

Suggested solution: If the warning window contains "Save as" then it should also contain a piece of text explaining why it contains "Save as" instead of "Save".