Convenient creation of command-line-driven executables for rendering diagrams using the SVG backend.

• defaultMain creates an executable which can render a single diagram at various options.
• multiMain is like defaultMain but allows for a list of diagrams from which the user can choose one to render.
• mainWith is a generic form that does all of the above but with a slightly scarier type. See Diagrams.Backend.CmdLine. This form can also take a function type that has a subtable final result (any of arguments to the above types) and Parseable arguments.

If you want to generate diagrams programmatically---i.e. if you want to do anything more complex than what the below functions provide---you have several options.

• Use a function with mainWith. This may require making Parseable instances for custom argument types.
• Make a new Mainable instance. This may require a newtype wrapper on your diagram type to avoid the existing instances. This gives you more control over argument parsing, intervening steps, and diagram creation.
• Build option records and pass them along with a diagram to mainRender from Diagrams.Backend.CmdLine.
• You can use renderSVG to render a diagram to a file directly; see Diagrams.Backend.SVG.
• A more flexible approach is to directly call renderDia; see Diagrams.Backend.SVG for more information.

For a tutorial on command-line diagram creation see http://projects.haskell.org/diagrams/doc/cmdline.html.

The mainWith method unifies all of the other forms of main and is now the recommended way to build a command-line diagrams program. It works as a direct replacement for defaultMain or multiMain as well as allowing more general arguments. For example, given a function that produces a diagram when given an Int and a Colour Double, mainWith will produce a program that looks for additional number and color arguments.

... definitions ...
f :: Int -> Colour Double -> Diagram SVG V2 Double
f i c = ...

main = mainWith f

We can run this program as follows:

$ ghc --make MyDiagram

# output image.svg built by `f 20 red`
$ ./MyDiagram -o image.svg -w 200 20 red