Where exactly did you get the themes? Is there a source tarball
somewhere? Sorry, I'm not on Fedora yet, just RedHat 9. I have tried
this with standard GNOME high-contrast themes, but can't reproduce it.

Are your GTK+ and gtkmm definitely in the same prefix?

The Gnome-Bluecurve theme came with Fedora Core, and the Industrial 
GTK theme is a compiled theme downloaded from http://art.gnome.org.

The Industrial theme is installed under my local users home 
directory. The prefix for gtk+-2.2.4 is /usr and the prefix for 
gtkmm-2.2.8 is /usr/local.. will that make a difference?

OK, I'm at this point now: I can reproduce the bug. I see what you
mean and I'm getting to it. I tried different combinations of Gtk and
Gtkmm classes. And now I'm diving into gtk code to look where the
actual drawing is done and which parameters are from where.

I tracked it down ... after all not so difficult but hey, who could
know that. Bluecurve takes advantage of 2 feature of gtkrc.
1) you can define many different sub-styles of a default style. They
inherent it's properties and you can override some of them to change
the look. -- Bluecurve overrides the default style in the menu-item
style and resets the color for prelighted (mouse-over) text.

2) you can apply those specialized style classes to certain
widget_classes by name. -- Bluecurve sets this to the menu-item style
for the `class` "GtkMenuItem" and the `widget_class`
"*.GtkMenuItem.*". I don't know the difference between those two, but
I hope to get to it. (there must be some doc on the net)

Now the thing is that gtkmm creates new subclasses of the Gtk+ ones
and changes the name to gtkmm__GtkClassName. Now gtk does not know
that the menu-item style should be applied to gtkmm__GtkMenuItem. You
can fix this by yourself if you add a line to the Bluecurve gtkrc
file, like:

widget_class "*.gtkmm__GtkMenuItem.*" style "bluecurve-menu-item"

this way it works, but this is very unpleasant to change everything.

I'll look further to find out wether there exists a better solution.

I have to admit that this is somewhat strange: the `class` directive
should sort this out. `class` is used in a hierarchical way. So any
widget that is of a class that is derieved from GtkMenuItem SHOULD get
this style too, but somehow it doesn't.

Hagen, exactly what line of what source code file should I look at to
see this?

No source code. This is intended to be common behavior for gtk+. The
documentation is at
http://developer.gnome.org/doc/API/2.0/gtk/gtk-Resource-Files.html
under paragraph "Pathnames and patterns".

I'll paste an extract:
Matching against class is a little different. The pattern match is
done against all class names in the widgets class hierarchy (not the
layout hierarchy) in sequence, so the pattern:

class "GtkButton" style "my-style"

will match not just GtkButton widgets, but also GtkToggleButton and
GtkCheckButton widgets, since those classes derive from GtkButton.

This means that gtkmm__GtkMenuItem s should be matched for

class "GtkMenuItem" style "my-style"

too. I somehow get the feeling that this is an error within Gtk+ but
then again it works for the GtkImageMenuItem class which is derieved
from GtkMenuItem. I really don't know how to track this bug down any
further:

I wrote sample applications to layout the class hirarchy and there it
seems perfectly normal to me. I wrote sample apps to check for style
setting to the accellabel and the menuitem and it seems all very well
there to. But I don't completely understand the styles in Gtk+ so I
can't proof it that way ...

*** This bug has been marked as a duplicate of 142417 ***