Figure.ternary: Support Frame's xaxis/yaxis/zaxis attributes to set axis settings for a/b/c axes

[Chuan1937]

Add ternary frame

Update the test pygmt/tests/test_ternary.py to use the new implemented Frame and Axis parameter classes.

Fixes partly #4494

[seisman]

xref: #4505 (comment)

[yvonnefroehlich]

Actually I would split this into two PRs, one for the code changes for the ternary frame itself and one for updating the tests.

[seisman]

Actually I would split this into two PRs, one for the code changes for the ternary frame itself and one for updating the tests.

Actually we have to update the tests in this PR to ensure the code changes are correct.

[seisman]

Still need to generate the baseline images and put them to dagshug, following the instructions at https://www.pygmt.org/dev/contributing.html#using-data-version-control-dvc-to-manage-test-images. Let me know if you'd like to do it or need help.

[Chuan1937]

Still need to generate the baseline images and put them to dagshug, following the instructions at https://www.pygmt.org/dev/contributing.html#using-data-version-control-dvc-to-manage-test-images. Let me know if you'd like to do it or need help.

ok, I can do it.

[Chuan1937]

@seisman
I tried pushing to DagsHub, but I'm not a collaborator yet.

[seisman]

You need to create an account on DagsHub, and then I can add you as a collaborator

[Chuan1937]

You need to create an account on DagsHub, and then I can add you as a collaborator

I have logged in using github.

[seisman]

Hmmm. I can't find you https://dagshub.com/Chuan1937

[Chuan1937]

Hmmm. I can't find you https://dagshub.com/Chuan1937

I changed to https://dagshub.com/Chuan1937

[seisman]

Ok. DOne

[seisman]

I just found one minor issue, which can be reproduced below

gmt begin map
  gmt makecpt -Cturbo -T0/80/10
  gmt ternary @ternary.txt -R0/100/0/100/0/100 -JX15c -Sc0.1c -C -Bafg
  gmt ternary @ternary.txt -R0/100/0/100/0/100 -JX15c -Sc0.1c -C -Bafg -B -Xw+1cba
gmt end show

As you can see, passing -Bafg alone doesn't plot the frame, which makes little sense. I think in this case, we should always pass -Bafg -B instead.