Re: Question about display engine

[martin rudalics]

> I think we should simply not merge the background color of the region
> face when its extend bit is reset.  Then the merged face will not have
> that background color.

Then which background color would we use?  That of the comment was
lost when setting up the current face for the iterator.

> I don't see a problem here.  A user who doesn't want the region face's
> background extend to the end of line wants only text (as opposed to
> whitespace after the newline) to have the region's background, and
> that's true both to regions that cross line boundaries and regions that
> end at a newline.

I agree that we don't want to extend the region's background.  But the
question I raised above still stands.

We could make :extend sticky in the sense that once an :extend for the
background has been defined, it will apply to all higher priority faces
as well.  This would make specifying a nil :extend value idempotent to
not specifying a value at all as you (IIRC) proposed earlier.  But the
mechanism then becomes considerably less powerful.

>> Maybe the display engine could consult, with the stop position
>> privilege triggered by the newline character in mind, whether the
>> extend_background false setting of the current face could result in
>> applying another, lower-priority face specified by font-locking and
>> consult the extend_background bit of the corresponding realized face.
>
> I don't think I understand this proposal.

Let's talk about it when we both see a problem here.

martin