Color histogram bars

[jo-mueller]

@dstansby

Fixes #58

This PR expands the feature histogram widget to color the histogram bars according to the color values in the displayed layer. Currently supported:

• Points layer
• Vectors layer

I'm not sure how tracks/shapes layer handle features and color, but this can be added relatively easily here.

Tests

• Pytest: I rewrote the existing tests a bit to make them more specific to vectors/points/other future supported layer and updated the respective baseline images. However, I didn't get the tests to pass with the call to pytest --mpl - it's probably the same issue as in this PR.
• Interactive test: I checked in the viewer that all controls behave as expected.

[jo-mueller]

pre-commit.ci autofix

[dstansby]

I've just fixed some failing tests (due to a new Matplotlib release) at #217, so worth merging or rebasing main.

[jo-mueller]

@dstansby

Strange. The figures in the baseline folders were saved from the tests themselves using

deepcopy(fig).savefig('./baseline/name_of_test_function.png')

but this generates an incorrect figures size, as it seems. Is there a correct way to save the generated test figures?

As for the other failing tests, I merged the current head into this branch but am not sure why tests are failing.

[jo-mueller]

Hi @dstansby ,

could you give me a hint on how to properly create the figures needed for the test to make the checks pass? Would be much appreciated :)

[dstansby]

I think the test figures were in the right place, but just needed updating due to changes that happened between opening the PR and now. I've merged in main, and updated the figures, so lets see if the tests pass now 😄

[dstansby]

Looking good, thanks for the PR 👍