[Yt-dev] Plot Types and Plot Collections

[Matthew Turk]

Hi everyone,

After talking to Sam and Devin at PiTP and then to Dave yesterday (at
UCSD, my new residence) it's become clear to me that the PlotTypes and
PlotCollections files -- which are remarkably unchanged over the last
2+ years of development, since they were first implemented -- have
become a bit stale and have some creeping bugs.  People have worked
around them, but it's time for an overhaul.

I'm writing with a new plan for how to handle plots, and I'm writing
because it might affect some of you.  The basic idea is that plots
will have valid and invalid states; invalid plots will be redrawn as
necessary.  Additionally, Pixelization into buffers will occur only
inside FixedResolutionBuffers, and every plot will have an associated
FRB.

So, a plot starts out, and it sets itself up and marks itself and its
colorbar as invalid.  We then save it, and it sees that it's invalid,
so it redraws.  This marks the colorbar as invalid (even though it
already is), and then the colorbar gets redrawn.  Both are now valid.
We then change the zlim, which marks the colorbar as invalid while the
image remains valid.  (Colorbar and colormap are essentially
inextricable here.)

So far, I think it's fine -- but the question comes in during user intervention.

So we have a valid state for our plot.  (The user can then mess with
it however they like, and on the next save, that messing with it will
still be there -- because it won't be marked as invalid -- which is a
huge advantage!)  When we change the width of the plot, then the image
becomes invalid.  But my real question is, what do we do if the user
then sets the zlim and then changes the width?

Set zlim: invalidate colorbar
Save: revalidate both
Set width: invalidate image

But, what happens to the colorbar?  Do we invalidate it, and then
reset it on next save?  That is, when we change the width, does that
override the user setting the colorbar?

Does anyone have any thoughts?  Thanks!

-Matt