[Plplot-devel] Locate mode improvements, (was Other problems with -locate option on x01c)

[Alan W. I. <ir...@be...>]

On Sun, 3 Mar 2002, Maurice LeBrun wrote:

> Maybe the message about locate mode terminated would be ok, as long as it's to
> stderr and not stdout.  As for restarting using "L" ... it's not the same
> thing.  Locate mode invoked by the driver just outputs the two world
> coordinates, whereas locate mode invoked by the user can do anything desired
> with the info.  And in fact the x01c example does present the info in
> different format, just to underscore that difference.

I draw a number of conclusions from what Maurice and Joao have said.

(1) Currently, there are actually two kinds of locate mode. One of them
("driver" locate mode) prints out x and y, but otherwise does not allow the
data to be retrieved by the programme. The other ("user" locate mode) does
allow programme access to the data, but it is only available from the C front
end.

The driver locate mode in its present form is not useful for my needs
because my programmes need access to the locate-mode data (x and y and
especially the key or mouse button that was pressed since that allows the
user to enter a wide variety of commands to help in interactive reduction of
spectra).  The user locate mode sounds more promising in that respect, but
it needs to make x, y, and key available to all front ends (i.e., probably
python in my case). Following what currently is possible with driver locate
mode, you should be able to enter or leave user locate mode at will by
pressing the appropriate keys, i.e., it should be available for all examples
for all front ends if an interactive driver with the right capabilities is
specified.

Thus, what I am really pressing for is a single coherent locate mode that
combines the best features of our two present locate modes plus a bit more.
I really need these improvements if I am going to use interactive PLplot for
my next research project, but there may be other improvements to locate mode
that we need to discuss as well so I would welcome such discussion.

(2) Whatever we decide to do with the present locate mode API, we need good
documentation of it.  I was very gratified to hear that Joao had such plans
and once he gets some words down I will be happy to turn it into docbook.
One thing that should be included in such documentation is the driver
requirements for locate mode. Of course, all the user-side locate mode stuff
we have been discussing should be documented as well.

Alan