Create Projection classes instead of strings

Description of the desired feature

The Figure methods take a projection argument that is using the same arguments as GMT -J ("M10i" for Mercator 10 inches). But a lot of projections have many arguments and it’s impossible to remember them all. A relatively simple alternative would be to implement classes (based on a single Projection class maybe) that take the projection arguments in the constructor (and so allows tab-completion). The key would be for these classes to define a __str__ method so that when str is called on them, they produce the GMT -J code. For example:

>>> proj = pygmt.Orthographic(central_longitude=10, central_latitude=52, width=10)
>>> print(str(proj))
G10/52/10

The plotting method pre-processing would only have to call str on projection, which works fine if you pass in a string as well.

Are you willing to help implement and maintain this feature? Yes but I’d welcome anyone else who wants to try 😃

[sixy6e]

Hi everyone, I’m just having a quick exploration into this issue whilst at the FOSS4G Oceania Community Day.

I think attrs is a good idea, so I’ll prototype out something over the weekend and see what you think. I have used attrs in a similar fashion to what is being described in this issue.

[sixy6e]

I’ll try to squish some time in and push through the last bits of the this over the next few weeks. Spare time completely disappeared for me the past year.