Re: Combining face and map stuff

[Eli Zaretskii]

> From: Stefan Monnier <address@hidden>
> Cc: address@hidden,  address@hidden
> Date: Tue, 12 Oct 2010 16:23:57 -0400
> 
> > 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.

So it's just a convenience feature, to avoid something like

  get existing text property value
  merge with another value
  put it back with add-text-property

in every package?