bug#46558: Interaction between font-lock-extend-region-wholelines and font-lock-extend-region-multiline

[Sébastien Miquel]

Hi,

In org-mode, blocks are fontified with the font-lock-multiline
property. When editing the line right before a block, the whole block
is needlessly refontified (use highlight-refontification-mode to
check).

This is because the font-lock-extend-region-wholelines extends the
region to the beginning of the next line, which has the
font-lock-multiline property. Then font-lock-extend-region-multiline
extends the region to the end of the block.

If a second block follows the first one, with no empty line between,
it is refontified as well.

Maybe font-lock-extend-region-multiline should check if the char
right before font-lock-end has the font-lock-multiline property as
well before extending the region. I've tried it, and haven't found any
issue in this use case.

--
Sébastien Miquel