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Consolidate agg-buffer examples.#11726

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Merged

jklymak merged 1 commit intomatplotlib:masterfromanntzer:canvasagg-examples

Jul 26, 2018

Merged

Consolidate agg-buffer examples.#11726

jklymak merged 1 commit intomatplotlib:masterfromanntzer:canvasagg-examples

Jul 26, 2018

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anntzer commentedJul 21, 2018•
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agg_oo_sgskip, webapp_demo_sgskip, and histogram_demo_canvasagg_sgskip
were all demonstrating the same thing (how to create a Figure outside of
pyplot, attach a canvas, and get the data out either saved to a file or
as a string. Consolidate them into a single example, with the minimal
amount of plotting. (PIL.Image.frombytes exists since Pillow 2.0 which
is the first version to support Py3.)

agg_buffer is very similar but uses another (worse?) technique to attach
an agg buffer; make data extraction simpler but otherwise keep it
separate for now.

Other related examples include:

agg_buffer_to_array which directly does
np.asarray(canvas.renderer._renderer), which is on the one side bad
as it uses a private API, but on the other hand the only way (AFAIK)
to access the underlying buffer without copy[*];
print_stdout_sgskip, which does use pyplot to set up the agg buffer.

Let's defer the discussion for these two examples to later.

[*] The poorly named buffer_rgba method actually does a copy (in PyBytes_FromStringAndSize). Note that the Py2 version used to return a Py2 buffer object, with no copy (https://github.com/matplotlib/matplotlib/blob/v2.2.2/src/_backend_agg_wrapper.cpp#L589). This (the buffer protocol) is also already implemented by the renderer object itself; it's just a matter of publically exposing it.

PR Summary

PR Checklist

Has Pytest style unit tests
Code is PEP 8 compliant
New features are documented, with examples if plot related
Documentation is sphinx and numpydoc compliant
Added an entry to doc/users/next_whats_new/ if major new feature (follow instructions in README.rst there)
Documented in doc/api/api_changes.rst if API changed in a backward-incompatible way

anntzer added the Documentation label

Jul 21, 2018

Consolidate agg-buffer examples.

870f851

agg_oo_sgskip, webapp_demo_sgskip, and histogram_demo_canvasagg_sgskipwere all demonstrating the same thing (how to create a Figure outside ofpyplot, attach a canvas, and get the data out either saved to a file oras a string.  Consolidate them into a single example, with the minimalamount of plotting.  (PIL.Image.frombytes exists since Pillow 2.0 whichis the first version to support Py3.)agg_buffer is very similar but uses another (worse?) technique to attachan agg buffer; make data extraction simpler but otherwise keep itseparate for now.Other related examples include:- agg_buffer_to_array which directly does  `np.asarray(canvas.renderer._renderer)`, which is on the one side bad  as it uses a private API, but on the other hand the only way (AFAIK)  to access the underlying buffer without copy;- print_stdout_sgskip, which does use pyplot to set up the agg buffer.Let's defer the discussion for these two examples to later.

anntzer force-pushed thecanvasagg-examples branch from1d02261 to870f851Compare

July 21, 2018 17:14

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ImportanceOfBeingErnest commentedJul 21, 2018

At leastagg_oo_sgskip is always been a standard example for people to link to from outside. Now the link adress has changed as it moved to/misc/, but at least the title did stay the same, so it's possible to find. If that example now vanishes, those links get completely broken. Is it necessary to completely remove it? I guess there is no way to do a http redirection for examples, right?

I know thatcanvas.renderer._renderer fails for some backends, at least for PyCharm's InterAgg. A bulletproof alternative would sure be desireable.

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anntzer commentedJul 21, 2018

I don't mind moving everything to agg_oo_buffer instead if that makes you more comfortable.

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ImportanceOfBeingErnest commentedJul 21, 2018

Ok, thinking about it, those links are broken anyways, so one needs to locate the examples through search anyways. The new name and title are much better now, so this is probably the more sustainable solution.
So what about mentioning the old names of the examples in the text, such that search finds them, something like

Note that this examples contains the content of the former agg_oo_sgskip, webapp_demo_sgskip, and histogram_demo_canvasagg_sgskip examples.

possibly in smaller font (if there exists a spinx rule for that).

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anntzer commentedJul 21, 2018

The link to agg_oo_sgkip won't be broken if I move everything to it...

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ImportanceOfBeingErnest commentedJul 21, 2018

Itis already broken. Versions of that example:

In 2.0.2 it was in/examples/api/agg_oo.html
In 2.1 and 2.2 it was in/gallery/api/agg_oo_sgskip.html
Now it is in/gallery/misc/agg_oo_sgskip.html

meaning that if it's moved again now, the link will be as broken as if you didn't do anything to it, because I strongly doubt that new links to the devdocs (devdocs/gallery/misc/agg_oo_sgskip.html) are already beeing created somewhere.

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anntzer commentedJul 21, 2018

Let's just leave this as it is then? I know that@tacaswell has thought about examples redirection but I'd rather have a general solution before starting to pepper docs with refs to no-longer-existing docs.

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ImportanceOfBeingErnest commentedJul 21, 2018

Ok, someone decided to break that link prior to this. So assuming there was a reason for this and since it got approved, this PR just builds on top and is fine by itself.