[Matplotlib-users] displaying coords

[Jean-Michel P. <jea...@ir...>]

Hello,

I recently worked on displaying plot coordinates from the example code 
'coord_demo.py' so that I now have a script that should provide the 
following features:

  - coords are displayed either when clicking a mouse button or when 
stopping the mouse cursor in the plot for a given time (based on a timer)

  - coords can be displayed in the console or directly in the figure (a 
kind of balloon)

  - displayed coords are the nearest plot point coords provided the 
number of point distances to compute between mouse and curves is low 
enough to preserve resources, coords are only displayed if the smallest 
computed distance is "small" enough

  - coords displaying is activated by calling a unique function, its 
args define the type of event that triggers coords displaying and the 
callback that renders these coords (users can then provide their own one)

The callback that displays coords in a balloon uses the 'text' function 
of matplotlib.matlab such that this feature shouldn't rely on any backend.

Unfortunately things don't work for all backends. The results are the 
following:
		console displaying	balloon displaying
		------------------	------------------
WXAgg			OK			OK
TkAgg			OK			hangs
GTKAgg		nothing happens		nothing happens

Note that I never tried in an interactive session and I currently use 
matplotlib 0.62.4. In case some people are interested in having a look 
at my code, I attached it. This is a module that can be run as a 
standalone script for testing.

If things finally get work, I plan to add a backend-independent "cross 
hair" as 'wxcursor_demo.py' does using lines, and to highlight the 
nearest point in the figure by changing its color and/or its marker (but 
I still don't know how to!). I also wonder about the opportunity to add 
a toolbar button for this kind of tool. This would certainly require 
further improvements since my script seems to interact with the zoom 
tool callback while drawing the rectangle with the mouse. Moreover I 
only tested it for a single plot at the moment.



JM. Philippe