Short version: I have to implement something very similar to making a
click in an URL in a mail message, cause the browser to open on that
page. From that description, it is clearly possible since
thunderbird+firefox can do it.

Now for the tricky details: the jump is ordered by a click on a button
in a Tcl/Tk (ie, wish) application. Ex hypothesis, at that time, the
'searcher' is on top and has focus (you can assume the click-to-type
focus mode in the WM, which BTW is KDM of KDE3). At that time, it
dumps the url in a well-known file.

You can also assume the 'browser' (written using OpenMotif 2.1) is
already started, and monitoring the file for changes. When it sees a
change, it will load and display the 'page' (without opening a new
window). During loading a modal progress dialog is on screen.

Currently the behaviour is that the browser comes on top (WM-wise)
during load, but immediately after the 'searcher' comes *back* on top,
having focus.

What I would like, of course, is that the 'browser' should have focus
and be on top.

No entry in the Motif FAQ about FOCUS seems to help. I have tried
XReconfigureWMWindow in the browser, no cigar.

I *could* of course try and look in the zilla sources how they do it
on Linux, but they are probably huge.

If you dont know the recipe to do what I need, the indication of an
Open-Source X-based application that is able to give itself the focus
and pop up on top, would help.