Bonsai

type UpdateResult aff model msg = { cmd :: Cmd aff msg, model :: model }

An update functions returns a new model and a possibly empty command

type ProgramState model msg = { dirty :: Boolean, dnode :: Element, model :: model, vnode :: VNode msg }

ProgramState tracks the current state of the model, vnode and dom element.

These are needed to advance the state in reaction to a Cmd message.

type Program aff model msg = { dbgEvents :: Boolean, dbgTiming :: Boolean, document :: Document, pending :: Ref (Array msg), renderer :: model -> VNode msg, state :: Ref (ProgramState model msg), updater :: model -> msg -> UpdateResult aff model msg, window :: Window }

Program describes the Bonsai program.

It is passed around in a ReaderT and stores callbacks and a ref to the pending commands. Event callbacks append to the list of pending commands, they will then be applied in the main event loop.

simpleTask :: forall msg aff. Aff aff msg -> Cmd aff msg

Produces a simple task (not cancellable, ony emits the return values

program :: forall msg model aff eff. ElementId -> (model -> msg -> UpdateResult aff model msg) -> (model -> VNode msg) -> model -> Window -> Eff (bonsai :: BONSAI, exception :: EXCEPTION | eff) (Program aff model msg)

Create initial environment for the Bonsai program.

plainResult :: forall msg model aff. model -> UpdateResult aff model msg

Creates an update result with empty command.

mapResult :: forall msg2 model2 msg1 model1 aff. (model1 -> model2) -> (msg1 -> msg2) -> UpdateResult aff model1 msg1 -> UpdateResult aff model2 msg2

Helper to map update results from sub-components

issueCommand :: forall msg model eff bff. Program bff model msg -> Cmd bff msg -> Eff (bonsai :: BONSAI | eff) Unit

Issue a command.

For pure commands, this will send the messages and request a redraw. For (asynchronous) task commands, the task will be started.

This can be used to start tasks, e.g. to initialize the model

emittingTask :: forall msg aff. (TaskContext aff msg -> Aff aff Unit) -> Cmd aff msg

Procudes a task that can emit multiple times

emitMessage :: forall msg aff. TaskContext aff msg -> msg -> Aff aff Unit

Emit helper for Tasks.

In an emitting task, use this function to emit messages.

debugProgram :: forall msg model aff eff. ElementId -> (model -> msg -> UpdateResult aff model msg) -> (model -> VNode msg) -> model -> Boolean -> Boolean -> Window -> Eff (bonsai :: BONSAI, exception :: EXCEPTION | eff) (Program aff model msg)

newtype ElementId

The ID of an element in the DOM

Constructors

• ElementId String

newtype Element

A DOM Element

window :: forall eff. Eff (bonsai :: BONSAI | eff) Window

Get the global javascript Window object

elementById :: forall eff. ElementId -> Document -> Eff (bonsai :: BONSAI | eff) (Maybe Element)

Get the element identified by id.

document :: forall eff. Window -> Eff (bonsai :: BONSAI | eff) Document

Get the global javascript Document object

newtype Window

The type for the global javascript window

type EventDecoder msg = Foreign -> BrowserEvent msg

A EventDecoder decodes a foreign to a BrowserEvent

newtype Document

The type for the global javascript document

data Cmd eff msg

A Command represents messages that should be applied to the Bonsai model

A command is either Pure (the constructor Cmd) or an asynchronous Task. The pure command simply contains the messages that will be emitted. The asynchronous Task gets an emitter function that it can use to emit messages at will.

There is currently no effectful synchronous command - there used to be, but it did not turn out very useful except in dumbed down examples.

There could be a helper function that expresses simple effectful commands as Tasks though.

There used to be a helper type for TaskContext -> Aff but for some reason it did not unify in user code. So the recommendation is to produce the command, not the function with complicated signature that goes inside a TaskCmd.

Constructors

• Cmd (Array msg)
• TaskCmd (TaskContext eff msg -> Aff eff Unit)

Instances

• Functor (Cmd eff)

data BONSAI :: Effect

Effect for public types

pureCommand :: forall msg aff. msg -> Cmd aff msg

Produces a pure command

emptyCommand :: forall msg aff. Cmd aff msg

Produces an empty command.