BUG: modifications through matplotlib engine cannot be properly displayed about yt HOT 5 CLOSED

Ah I missed what you said "ahead of MPL API". Now I got it how it works, thanks! @neutrinoceros

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I think what you described is an unfortunate but known limitation of yt's callback system: in general, using yt API to modify a plot has, by design, no immediate effect, and most computations and IO operations are delayed until the figure is rendered (in a REPL, or when render or save are called). This system helps a lot with performance, however it works by redrawing the entire figure each time a render is needed, which means that any modification done directly with MPL (bypassing yt) will be erased on the next render.
I never could find a nice way to better support this usage, but if we could better integrate with MPL API, it'd make part of yt's completely redundant and lead to great simplifications.

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hi @xshaokun , thanks for noticing !

I think what's happening is that the image (and most of the plot) is lazy-generated at some point ™️ between calls to MPL API and .save(), which invalidates everything done by the script.
It's trivially fixed by forcing rendering at a controlled point ahead of MPL API calls with slc.render(), though I wonder why this wasn't necessary when this example was written.

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Thank @neutrinoceros for your reply!

It's trivially fixed by forcing rendering at a controlled point ahead of MPL API calls with slc.render(), though I wonder why this wasn't necessary when this example was written.

It can produce an expected output in docs. However, if some plot window methods are called, it will break again. For example, methods like slc.set_origin("lower-center-window") or slc.annotate_timestamp() will make slc.save() and fig.savefig("sloshing.png") giving different results. Output from the former only applied the modifications by plot_window methods, while output from the latter only applied the modifications by matplotlib engine, even if slc.render() is used (actually it will overwrite the modifications from matplotlib engine).

It seems like I was modifying different objects with different approaches. Does it make sense?

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I'm okay with the current design as soon as I know what's happening inside the box. I have to dive into the source code to figure out that render will erase old axes, which should be told explicitly in docs so that users can use MPL API properly. Many thanks for your help!

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