Processing scripting, mid interface. Unlike the basic interface (see Graphics.Web.Processing.Basic) the script is more guided by the types. However, the output is less predictable, since it does some tricks in order to obtain semantics that are more coherent with Haskell. The difference is small, but let's say that this module has more freedom writing the output code. It also applies code optimizations, so the output code may look different (see execScriptM and Graphics.Web.Processing.Optimize).

How to work with it?

Everything is done within the ScriptM monad, a state monad that controls the entire script, including the preamble, draw loop, setup, etc. The interaction with the different parts of the script is done via events (see EventM). For example, the Draw event controls the draw loop.

 mouse :: ScriptM Preamble ()
 mouse = do
   on Setup $ do
      size screenWidth screenHeight
      fill $ Color 255 255 255 255
   on Draw  $ do
      background $ Color 0 0 0 255
      p <- getMousePoint
      circle p 10

Note that to make it work, the context of the script must be Preamble.

Interaction with variables is done via the ProcVarMonad class. This class defines methods to interact with variables in both the ScriptM monad and the EventM monad. To store custom types in variables, see the Graphics.Web.Processing.Mid.CustomVar module.

Once your script is complete, use execScriptM to get the result code.