modify text properties in read-only buffer

Question

I am annotating parts of text in an emacs buffer using text properties. The code I am using looks something like this:

(set-text-properties beg end nil)  ; clear properties
(add-face-text-property beg end city-name-face)
(put-text-property beg end 'field "city-name")

where beg and end are the markers in-between of which the property is set, and city-name-face is defined elsewhere in code.

Everything works fine, except when I occasionally press a wrong key and modify the text in the file. However, I want the text (as sequence of characters) to be immutable and modify only its properties.

Is it possible?

Answer 1

You can use read-only-mode, this prevents you from editing the buffer.

However, that prevents you from setting properties. Fortunately, this can be fixed by using something like:

 (let ((buffer-read-only nil))
     YOUR-CODE-GOES-HERE).