Reverted a previous change to artist transform setting. Fixes legend bug.

[pelson]

On master, the following code fails to put the markers in a legend in the correct place:

import matplotlib.pyplot as plt

plt.subplot(222)

plt.subplot(223)
plt.scatter(range(10), range(10), label='foo')
plt.legend()

plt.show()

It turns out this is a result of a previous pull request of mine (#1090). This PR fixes this regression (and adds a suitable test). I will milestone this for 1.2 as it is a pretty critical bug fix.

[WeatherGod]

That's really strange. I would have considered the "t is not None" test as being superior to blindly setting the boolean to True. Maybe some code somewhere is fiddling around with the _transform attribute directly when it shouldn't?

[pelson]

That's really strange. I would have considered the "t is not None" test as being superior to blindly setting the boolean to True

Me too! The Artist._transformSet attribute is used by the Artist.is_transform_set method. The only place this is used is in axes.py and offsetbox.py. I believe the issue is in offsetbox, which checks is_transform_set and if it isn't, adds a generic transform (from offsetbox.DrawingArea.get_transform()). All this stuff is pretty deep in mpl, and I am a little hesitant to change some of this stuff, hence I reverted my own change.

[travisbot]

This pull request fails (merged 654b2922 into cf7618c).

[mdboom]

Thanks for finding this and tracking this down. I think what's not clear is that a transform of None is set, that's equivalent to an identity transform, and should be treated as an explicit transform having been set as far as the offsetbox is concerned. I think this change is correct, though I haven't run it against the test suite to see if it produces additional failures.

[pelson]

though I haven't run it against the test suite to see if it produces additional failures

You were right to have your suspicions. I do get failures as a result of this. Back to the drawing board... might not find a solution to this until tomorrow.

[travisbot]

This pull request fails (merged 4965b5df into cf7618c).

[pelson]

Ok. I have solved this issue the proper way. I did a lot of reading of the legend code (phew, its not particularly easy to follow), found the problem (the transforms weren't being set correctly) and fixed a couple of typos.

Unfortunately, my editor had a setting enabled to fix the whitespace problems automatically, which adds a little bit of noise to this PR. It wouldn't be unreasonable to ask me to revert them, but I am keeping them for now as they do improve the overall readability of the code (and hence my sanity while I was debugging this).

[mdboom]

The fancy_test fails for me due to text differences. I think either the freetype version needs to be restricted (not ideal), or the text needs to be changed to use characters that don't exhibit these differences.

[pelson]

or the text needs to be changed to use characters that don't exhibit these differences

@mdboom any advice on how best to go about this?

[mdboom]

Maybe the best/easiest thing to do is to just take the text out -- the legend should layout good enough for the purposes of the test without it.