On Feb 9, 2006, at 2:07 p, Bob Hanson wrote:
I'm looking at the Jmol callback issue.
<snip>
I propose that there be a fundamentally different mechanism that
does not rely upon callback functions (but could be backward-
compatible with these if desired).
I think this is an excellent idea. Miguel has been hinting at
something like this for a while, but the need for it never reached
'critical mass' in the user community (or so I infer from the
responses over the months).
The details of the implementation aren't particularly important
right now (on this list). But, basically, it would involve one
JavaScript timer per applet and the idea of "polling" -- the web
page periodically polls the applet -- say, 10 times per second, --
looking for changes of interest to particular properties of the model.
It's relatively simple to implement -- that's not the issue. The
issue is this:
AS A USER, WHAT DO YOU WANT?
as a resource developer, I want a way to ask the applet for the
status of something, have the applet respond in some logical syntax,
and then do with that info whatever I please. for example:
what atom was last picked?
what is the orientation of the molecule?
which atoms are colored red?
what color is this atom?
what is the format of this atom?
is this atom visible?
how many Fe atoms are present in the structure?
what is the currently selected atomset?
which protein residues are in alpha helices?
...
a) Do you implement callbacks? If so, which ones?
yes, pickCallback and messageCallback. in some applications, I use
these extensively. it is painful, does not work consistently, and
severely hampers platform and browser compatibility. this is no
reflection at all on Miguel's implementation of them; as he has said
many times before, callbacks are not the ideal solution.
b) What WOULD you use if you had it available?
callbacks? none, if I didn't have to. :-)
c) What sort of information (exactly) are you looking for?
see examples above. mainly, state of atoms. but given some time, I
could probably think up a few new ideas.
d) Is there a particular format that you would like to see,
other than just the current text-stream of messages?
that will depend on the data, I think. ask for a number, get a
number. ask for a set, get an array. ask for a color, get a string.
perhaps some kind of javascript Object could handle all cases?
e) Is it important to you that this mechanism be backward
compatible?
since this is a brand new mechanism, I don't think that backwards-
compatibility is even an issue.
MORE SPECIFC QUESTION:
1. There are currently four callbacks:
animFrameCallback
loadStructCallback
pickCallback
messageCallback
Each of these fulfills an obvious need.
Should there be more "callback-like" options?
My primary use of callbacks revolves around polling the applet for
information about the structure, or for capturing commands sent to
the applet by the user. and really, the former is simply a
modification of the latter - with my javascript code in place of the
user, since I have to send a command to the applet in order to find
out something useful. to me, this functionality should not be in the
realm of the callbacks, but handled by something else - exactly what
you are proposing, Bob.
as far as querying the applet for its own state - I suppose callbacks
could have a purpose here, though I don't use them as such (I
generally just watch the applets[] array, for example).
regards,
tim
--
Timothy Driscoll em: [EMAIL PROTECTED]
molvisions - see. grasp. learn. ph: 919-368-2667
<http://www.molvisions.com/> im: molvisions
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