Re: Combining face and map stuff

[Stefan Monnier]

>> Package foo wants to add `face' stuff and package bar also wants to add
>> `face' stuff.  If both add it to the same piece of text, we have
>> a problem, and if they want to update it later they have to know who
>> "owns" the particular value (i.e. who it comes from) to know whether it
>> should be updated or not.

> In that case, I'm sorry, but I must ask the same question again: how
> will the display engine know which face to display?

> Let's say we have a buffer, in which both package foo and package bar
> defined different faces for the same piece of text.  Which one of them
> will be displayed, and how would the display engine know to choose it?

Internally, one of them sets the property (foo . face) to <face1>, the
other one sets the property (bar . face) to <face2>, and when these are
set, the `face' property gets set to (<face1> <face2>).  The display
engine only looks at the `face' property, just as before.


        Stefan