RE: why does occur depropertize matching lines?

[Drew Adams]

    >         Most faces don't change background color.  Only very
    special faces
    >         (that are very rarely used in buffers on which occur
    is usually
    >         called) have background different from default.
    >
    >     Yes, most such faces are used for temporary highlighting.
    >
    > I don't think these assumptions should be made. Users can
    define faces (for
    > font-lock or anything else) any way they want, including changing the
    > background.
    >

    If you don't want the face changed why not add an overlay arrow like
    in gdb mode?

Sorry, I don't understand what you are suggesting. Don't want what face
changed?

My point was that we should not assume that most faces do not change the
background color ("very rarely") and that most such faces are only for
temporary highlighting (vs, for instance, font-locking).