On Mon, Oct 19, 2009 at 2:10 PM, Mojca Miklavec <
mojca.miklavec.lists@gmail.com> wrote:

> On Sun, Oct 18, 2009 at 21:11, Aurelien Giraud wrote:
> > Hello,
> >
> > I am new to ConTeXt and I have looked on the internet for a way to do
> > something special. Unfortunately I have not found any solution.
> >
> > I hope this is the right place for such a question. I apologise
> otherwise.
> >
> > I would like to highlight (e.g. put in bold, or change the color...) any
> > character on a page which sits on a chosen path. I would like to be able
> to
> > position for instance an invisible circle on a page and have all the
> > characters "in contact" with this circle change color so that the circle
> > become visible via these characters. Is it something I could do with
> > ConTeXt?
>
> If I remember well, there are in pdftex some primitives about (x,y)
positions of an object
in a page.
Maybe one can use these primitives to dissect a vbox
and analyze its nodelist to mark the glyph node that have x y such that

| (x-xc)^2 + (y-yc)^2 - r | ≤ 𝛜

where
(xc,yc) are the coordinate of the circle respect to the page
r >0 is the radius
𝛜 >0 is the tolerance

-- 
luigi