Styling custom gtk widgets

[ax487 <ax487 gmx de>]

Hello all,

I have some questions regarding the CSS styling system. I have given a
canvas with certain pages on top of it. I want to draw a frame around
each of the pages. I use gtk_render_frame for this. However, this leads
to a couple of complications:

1. I noticed that in the default setting nothing is rendered at all.
This seems to be due to the fact that the border style is not defined. I
have to add a class to the style context using for example
"gtk_style_context_add_class(context, classname)". I am unclear about
the class to use for this. It should be such that the frame is visible
and there is a clear distinction between focused and unfocused. Is there
a suitable class?

2. Assume that I want to have the possibility to modify the style using
a CSS file. Can I achieve an "override" effect in the CSS file (like this)?

MyWidget {
  // command to use the same style as that of some other class
  modification: value;
}

3. The pages I want to display are rectangles, however in general the
frames used by standard themes might have a border-radius. This means
that if I draw the frame over the page then the edges of the page
overlap. Is there some way of clipping the cairo_t* according to the
rendered frame?

I would be interested in something which integrates well with different
existing themes. Am I going about this in the right way?

ax487