[QUESTION] Fontlocking for source block implementation

[Huan Nguyen]

I’d like to know how the fontlocking is implemented for the source blocks 
(#begin_src lang #end_src). Can someone give me some functions/files I can take 
a look at.

For developing a markup based language mode. A colleague kinda has it but it 
applies the fontlocking to the entire buffer, overwriting the mode’s 
fontlocking.

Best regards
Nguyen Thieu Huan