| Safe Haskell | None |
|---|---|
| Language | Haskell2010 |
Myxine.Handlers
Description
In order to react to user events in the browser, we need to specify what effect
each event of interest should have on the model in our Page. To do
this, runPage asks that we construct up-front a set of Handlers
describing this.
Handlers is a Monoid: the mempty Handlers listens to no events.
Singleton Handlers can be created using the onEvent function, and they can
be joined together using <>.
This module is useful when you are building your own page event handling
abstraction, for instance, if Reactive isn't right for your purposes.
However, it is not necessary to use this module directly if you are building a
reactive page using that high-level abstraction.
Synopsis
- data Handlers model
- onEvent :: EventType props -> [TargetFact] -> (props -> model -> IO (Propagation, model)) -> Handlers model
- handle :: Handlers model -> PageEvent -> model -> IO model
- handledEvents :: Handlers model -> [Some EventType]
- focusHandlers :: forall model model'. Traversal' model model' -> Handlers model' -> Handlers model
- data TargetFact
- tagIs :: Text -> TargetFact
- attrIs :: Text -> Text -> TargetFact
- window :: TargetFact
- data Propagation
Documentation
A set of handlers for events, possibly empty. Create new Handlers using
onEvent, and combine Handlers together using their Monoid instance.
onEvent :: EventType props -> [TargetFact] -> (props -> model -> IO (Propagation, model)) -> Handlers model Source #
Create a handler for a specific event type by specifying the type of event and the monadic callback to be invoked when the event occurs.
The provided callback will be given the properties props of this particular
event, and the current model of a page. It has the option to do arbitrary
IO, and to return a possibly-changed model. It also must specify whether
or not the event should continue to propagate outwards to other handlers, by
giving a Propagation (either Bubble or Stop).
The callback will only be invoked when an event occurs which matches the
conjunction of the specified list of TargetFacts. For instance, to
constrain a handler to only events on div elements with class="foo", we
would use the TargetFact [tagIs "div", "class" .attrIs "foo"]
Notice that each variant of EventType has a type-level index describing
what kind of data is carried by events of that type. This means that, for
instance, if you want to handle a Click event, which has the type
'EventType MouseEvent', your event handler as created by on will be
given access to a MouseEvent data structure when it is invoked. That is to
say:
onEventClick[tagIs"div", "class" `'attrIs'\` "foo"] (\properties@MouseEvent{} model -> do print properties print model pure (Bubble, model)) ::Showmodel =>Handlersmodel
A full listing of all available EventTypes and their corresponding property
records can be found in the below section on types and properties of
events.
handle :: Handlers model -> PageEvent -> model -> IO model Source #
Dispatch all the event handler callbacks for a given event type and its corresponding data.
Event handlers for this event type will be called in the order they were
registered (left to right) with the result of the previous handler fed as the
input to the next one. If any event handler in the chain returns Stop, then
propagation stops at the current Target for that handler.
handledEvents :: Handlers model -> [Some EventType] Source #
Get a list of all the events which are handled by these handlers.
focusHandlers :: forall model model'. Traversal' model model' -> Handlers model' -> Handlers model Source #
Extend a set of Handlers that manipulate some smaller model' to
manipulate some larger model, using a Traversal' between the two model
types. Whenever a handler is invoked, it will be called with each extant
target of the specified Traversal'.
data TargetFact Source #
A fact about a Target, such as it having a particular tag or having a
particular attribute equal to a particular value.
You can construct a TargetFact using tagIs, attrIs, or
window.
Instances
tagIs :: Text -> TargetFact Source #
A TargetFact specifying that the target must have the HTML tag given;
otherwise, this handler will not fire.
attrIs :: Text -> Text -> TargetFact Source #
A TargetFact specifying that the target must have the HTML attribute
given, with the exact value specified; otherwise, this handler will not fire.
window :: TargetFact Source #
A TargetFact specifying that the target must be the root DOM element,
that is, the window object.
data Propagation Source #
Indicator for whether an event should continue to be triggered on parent
elements in the path. An event handler can signal that it wishes the event to
stop propagating by returning Stop.
Constructors
| Bubble | Continue to trigger the event on parent elements |
| Stop | Continue to trigger the event for all handlers of this element, but stop before triggering it on any parent elements |