This is the simplest way to render diagrams, and is intended to be used like so:

... other definitions ...
myDiagram = ...

main = defaultMain myDiagram

Compiling a source file like the above example will result in an executable which takes command-line options for setting the size, output file, and so on, and renders myDiagram with the specified options.

On Unix systems, the generated executable also supports a rudimentary "looped" mode, which watches the source file for changes and recompiles itself on the fly.

Pass --help to the generated executable to see all available options. Currently it looks something like

./Program

Usage: ./Program [-w|--width WIDTH] [-h|--height HEIGHT] [-o|--output OUTPUT]
                 [--loop] [-s|--src ARG] [-i|--interval INTERVAL]
  Command-line diagram generation.

Available options:
  -?,--help                Show this help text
  -w,--width WIDTH         Desired WIDTH of the output image
  -h,--height HEIGHT       Desired HEIGHT of the output image
  -o,--output OUTPUT       OUTPUT file
  -l,--loop                Run in a self-recompiling loop
  -s,--src ARG             Source file to watch
  -i,--interval INTERVAL   When running in a loop, check for changes every INTERVAL seconds.

For example, a couple common scenarios include

$ ghc --make MyDiagram

  # output image.png with a width of 400px (and auto-determined height)
$ ./MyDiagram -o image.png -w 400

  # output 200x200 dia.pdf, then watch for changes every 10 seconds
$ ./MyDiagram -o dia.pdf -h 200 -w 200 -l -i 10

multiMain is like defaultMain, except instead of a single diagram it takes a list of diagrams paired with names as input. The generated executable then takes a --selection option specifying the name of the diagram that should be rendered. The list of available diagrams may also be printed by passing the option --list.

Example usage:

$ ghc --make MultiTest
[1 of 1] Compiling Main             ( MultiTest.hs, MultiTest.o )
Linking MultiTest ...
$ ./MultiTest --list
Available diagrams:
  foo bar
$ ./MultiTest --selection bar -o Bar.png -w 200

animMain is like defaultMain, but renders an animation instead of a diagram. It takes as input an animation and produces a command-line program which will crudely "render" the animation by rendering one image for each frame, named by extending the given output file name by consecutive integers. For example if the given output file name is foo/blah.png, the frames will be saved in foo/blah001.png, foo/blah002.png, and so on (the number of padding digits used depends on the total number of frames). It is up to the user to take these images and stitch them together into an actual animation format (using, e.g. ffmpeg).

Of course, this is a rather crude method of rendering animations; more sophisticated methods will likely be added in the future.

The --fpu option can be used to control how many frames will be output for each second (unit time) of animation.

gifMain takes a list of diagram and delay time pairs and produces a command line program to generate an animated GIF, with options GifOpts. "Delay times are in 1/100ths of a second."

Example usage:

  $ ghc --make GifTest
  [1 of 1] Compiling Main             ( GifTest.hs, GifTest.o )
  Linking GifTest ...
  ./GifTest --help
  GifTest

  Usage: GifTest [-w|--width WIDTH] [-h|--height HEIGHT] [-o|--output OUTPUT]
  [--dither] [--looping-off] [--loop-repeat ARG]
  Command-line diagram generation.

  Available options:
   -?,--help                Show this help text
   -w,--width WIDTH         Desired WIDTH of the output image
   -h,--height HEIGHT       Desired HEIGHT of the output image
   -o,--output OUTPUT       OUTPUT file
   --dither                 Turn on dithering.
   --looping-off            Turn looping off
   --loop-repeat ARG        Number of times to repeat

Extra options for animated GIFs.

This data declaration is simply used as a token to distinguish the cairo backend: (1) when calling functions where the type inference engine would otherwise have no way to know which backend you wanted to use, and (2) as an argument to the Backend and Renderable type classes.