Problem moving items in a canvas

[Luis López]

Hi!

I am an astronomy teacher, and I'm preparing a program to analyze stellar
spectra with my pupils. It's going on well (I think!), but I have a strange
problem that I can't solve by myself.

The principal code is in "espectro-visual.lisp" ("fits.lisp" is a kind of
little 'library' to open fits image files, an astronomical standard; you
can visualize them with programs like "SaoImage DS9"). You run the program
with '(espectro-visual)'. To reproduce the problem I think I'd better guide
you step by step:

1) You click in 'Create profile..." and choose 'solar-spectrum.fit' (you
can download this file (~1MB) from
http://www.astro.cnba.uba.ar/solar-spectrum.fit).
2) Then you move over the profile, and -pressing the mouse right-button-
move a dozen or so pixels left or right and release the button: you'll see
a line and a number under the 'barycenter' of the zone (astronomically, you
should choose an spectral line (one of those 'valleys' here and there), but
that doesn't matter now).
3) If you press the mouse left-button over the number created, you can move
it around the canvas (I want to be able to do it, to avoid the 'cluttering'
of labels).

Now, the problem: As soon as I leave the canvas with the mouse, if I
re-enter the canvas I'm no longer able to move the labels again! I can do
it with new labels, but if I leave the canvas the problem applies to them
too.

Thank you very much, and please excuse me if I didn't explain myself very
well.

Luis López
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