Re: Font Locking issue: Need help/advice

[David Engster <deng@randomsample.de>]

> - What happens on the GIF?  How I can fix this? How to avoid similar
>   in the future?

What happens here is that the initial font-lock goes over the whole
currently visible section, but as soon as you edit one line, font-lock
will be called only for the part of the buffer that has changed, and it
seems your font-lock rules work differently in this case because the
context has changed.

> - In fact, I would like to be able to independently receive the
>   answer to the question "Why did this happen?" so I'm interesting
>   on debugging practices.  How to debug similar issues?

For better understanding how font-lock actually works, I highly
recommend using font-lock-studio

https://github.com/Lindydancer/font-lock-studio

Also, take a look at the other linked packages in the description. In
your case, 'highlight-refontification' could be useful to see which
parts of the buffer actually get refontified when you edit it.

-David