Allow Latex expressions in single-line titles and Cartesian axes labels

[PaulWessel]

Description of proposed changes

See #4563 for background. This PR implements the ability to place Latex expressions in titles and labels. Users who wish to use this feature must have a working installation of latex and dvips as well as recommended fonts. Because a title may contain a mix of text and equation, I change the default Latex font to match the corresponding title or label font chosen in GMT. The correspondence should work for all of our standard fonts, e.g., Helvetica, Times-Roman, Courier, Bookman, Palatino, etc.

Some limitations that may be relaxed later:

1. Only single-line titles can have Latex expressions in them.
2. The subplot -Theading has not been updated for latex (nor multi-line headings) yet.
3. colorbar may also need some more work.

I have updated the documentation and added two test scripts (latextitle.sh and latexlabel.sh). The output of the latter looks like this:

Feel free to test-drive this PR to possibly expose any issues. Once acceptable we also need to update the run-time dependency entries on the wiki and Building.

[PaulWessel]

I believe I have completed this pull request by also allowing Latex-expressions in pstext (except for paragraph mode -M). I have added a new test latext.sh to demonstrate this latest feature:

Please give this PR a review now, @joa-quim, @seisman and @meghanrjones.

[PaulWessel]

Also fixed that remaining #break; to <break>

[seisman]

@PaulWessel Do you mind moving the 4 latex tests into a separate directory, e.g, latex? It would be easier to exclude them from the tests if latex or dvips are not found.

[PaulWessel]

@PaulWessel Do you mind moving the 4 latex tests into a separate directory, e.g, latex? It would be easier to exclude them from the tests if latex or dvips are not found.

Good idea, will do soon but in the middle of Xcode debug on another branch... Or you can do it, create a latex test folder and move the ones from psbasemap and pstext I think. Not sure about doc/scripts/GMT_latex.sh though as not a test.

[seisman]

After installing the full mactex via homebrew brew install --cask mactex-no-gui, the LaTeX feature now works well for me.

There are still a few comments to address:

• Allow Latex expressions in single-line titles and Cartesian axes labels #4566 (comment)
• Allow Latex expressions in single-line titles and Cartesian axes labels #4566 (comment)

We may also need to add instructions to install LaTeX in the wiki.

[PaulWessel]

I recommend fixing the warning that
gmt/dbuild/doc/rst/source/cookbook/gmt-latex.rst: WARNING: document isn't included in any toctree
by adding cookbook/gmt-latex to the toctree in doc/rst/source/cookbook.rst (the toctree starts at Line 35, gmt-latex could go right below postscript-fonts at L50) before merging. GitHub only allows suggesting line changes to files that have been edited, which is why I cannot suggest this change directly through a PR review.

Thanks, now committed

[PaulWessel]

After installing the full mactex via homebrew brew install --cask mactex-no-gui, the LaTeX feature now works well for me.

There are still a few comments to address:

• #4566 (comment)
• #4566 (comment)

We may also need to add instructions to install LaTeX in the wiki.

Warnings fixed. instructions for wiki next but not in this repo.

[PaulWessel]

Yippie!

[seisman]

FYI, I created a wiki page for "how to install LaTeX" at https://github.com/GenericMappingTools/gmt/wiki/Install-LaTeX-for-GMT-LaTeX-Integration.