# Module Lwt_js_events

    module Lwt_js_events: sig .. end

Programming mouse or keyboard events handlers using Lwt

Reminder: Event capturing starts with the outer most element in the DOM and works inwards to the HTML element the event took place on (capture phase) and then out again (bubbling phase).

## Create Lwt threads for events

    val make_event : (#Dom_html.event as 'a) Js.t Dom_html.Event.typ ->
           ?use_capture:bool -> #Dom_html.eventTarget Js.t -> 'a Js.t Lwt.t

`make_event ev target` creates a Lwt thread that waits for the event `ev` to happen on `target` (once). This thread is cancellable using . If you set the optional parameter `~use_capture:true`, the event will be caught during the capture phase, otherwise it is caught during the bubbling phase (default).

    val seq_loop : (?use_capture:bool -> 'target -> 'event Lwt.t) ->
           ?cancel_handler:bool ->
           ?use_capture:bool ->
           'target -> ('event -> unit Lwt.t -> unit Lwt.t) -> unit Lwt.t

`seq_loop (make_event ev) target handler` creates a looping Lwt thread that waits for the event `ev` to happen on `target`, then execute handler, and start again waiting for the event. Events happening during the execution of the handler are ignored. See `async_loop` and `buffered_loop` for alternative semantics.

For example, the `clicks` function below is defined by:

`let clicks ?use_capture t = seq_loop click ?use_capture t`

The thread returned is cancellable using . In order for the loop thread to be canceled from within the handler, the latter receives the former as its second parameter.

By default, cancelling the loop will not cancel the potential currently running handler. This behaviour can be changed by setting the `cancel_handler` parameter to true.

    val async_loop : (?use_capture:bool -> 'target -> 'event Lwt.t) ->
           ?use_capture:bool ->
           'target -> ('event -> unit Lwt.t -> unit Lwt.t) -> unit Lwt.t

`async_loop` is similar to `seq_loop`, but each handler runs independently. No event is thus missed, but since several instances of the handler can be run concurrently, it is up to the programmer to ensure that they interact correctly.

Cancelling the loop will not cancel the potential currently running handlers.

    val buffered_loop : (?use_capture:bool -> 'target -> 'event Lwt.t) ->
           ?cancel_handler:bool ->
           ?cancel_queue:bool ->
           ?use_capture:bool ->
           'target -> ('event -> unit Lwt.t -> unit Lwt.t) -> unit Lwt.t

`buffered_loop` is similar to `seq_loop`, but any event that occurs during an execution of the handler is queued instead of being ingnored.

No event is thus missed, but there can be a non predictible delay between its trigger and its treatment. It is thus a good idea to use this loop with handlers whose running time is short, so the memorized event still makes sense when the handler is eventually executed. It is also up to the programmer to ensure that event handlers terminate so the queue will eventually be emptied.

By default, cancelling the loop will not cancel the (potential) currently running handler, but any other queued event will be dropped. This behaviour can be customized using the two optional parameters `cancel_handler` and `cancel_queue`.

    val async : (unit -> 'a Lwt.t) -> unit

`async t` records a thread to be executed later. It is implemented by calling yield, then Lwt.async. This is useful if you want to create a new event listener when you are inside an event handler. This avoids the current event to be catched by the new event handler (if it propagates).

## Predefined functions for some types of events

    val click : ?use_capture:bool ->
           #Dom_html.eventTarget Js.t -> Dom_html.mouseEvent Js.t Lwt.t

    val dblclick : ?use_capture:bool ->
           #Dom_html.eventTarget Js.t -> Dom_html.mouseEvent Js.t Lwt.t

    val mousedown : ?use_capture:bool ->
           #Dom_html.eventTarget Js.t -> Dom_html.mouseEvent Js.t Lwt.t

    val mouseup : ?use_capture:bool ->
           #Dom_html.eventTarget Js.t -> Dom_html.mouseEvent Js.t Lwt.t

    val mouseover : ?use_capture:bool ->
           #Dom_html.eventTarget Js.t -> Dom_html.mouseEvent Js.t Lwt.t

    val mousemove : ?use_capture:bool ->
           #Dom_html.eventTarget Js.t -> Dom_html.mouseEvent Js.t Lwt.t

    val mouseout : ?use_capture:bool ->
           #Dom_html.eventTarget Js.t -> Dom_html.mouseEvent Js.t Lwt.t

    val keypress : ?use_capture:bool ->
           #Dom_html.eventTarget Js.t -> Dom_html.keyboardEvent Js.t Lwt.t

    val keydown : ?use_capture:bool ->
           #Dom_html.eventTarget Js.t -> Dom_html.keyboardEvent Js.t Lwt.t

    val keyup : ?use_capture:bool ->
           #Dom_html.eventTarget Js.t -> Dom_html.keyboardEvent Js.t Lwt.t

    val input : ?use_capture:bool -> #Dom_html.eventTarget Js.t -> Dom_html.event Js.t Lwt.t

    val change : ?use_capture:bool -> #Dom_html.eventTarget Js.t -> Dom_html.event Js.t Lwt.t

    val dragstart : ?use_capture:bool ->
           #Dom_html.eventTarget Js.t -> Dom_html.dragEvent Js.t Lwt.t

    val dragend : ?use_capture:bool ->
           #Dom_html.eventTarget Js.t -> Dom_html.dragEvent Js.t Lwt.t

    val dragenter : ?use_capture:bool ->
           #Dom_html.eventTarget Js.t -> Dom_html.dragEvent Js.t Lwt.t

    val dragover : ?use_capture:bool ->
           #Dom_html.eventTarget Js.t -> Dom_html.dragEvent Js.t Lwt.t

    val dragleave : ?use_capture:bool ->
           #Dom_html.eventTarget Js.t -> Dom_html.dragEvent Js.t Lwt.t

    val drag : ?use_capture:bool ->
           #Dom_html.eventTarget Js.t -> Dom_html.dragEvent Js.t Lwt.t

    val drop : ?use_capture:bool ->
           #Dom_html.eventTarget Js.t -> Dom_html.dragEvent Js.t Lwt.t

    val focus : ?use_capture:bool -> #Dom_html.eventTarget Js.t -> Dom_html.event Js.t Lwt.t

    val blur : ?use_capture:bool -> #Dom_html.eventTarget Js.t -> Dom_html.event Js.t Lwt.t

    val scroll : ?use_capture:bool -> #Dom_html.eventTarget Js.t -> Dom_html.event Js.t Lwt.t

    val submit : ?use_capture:bool -> #Dom_html.eventTarget Js.t -> Dom_html.event Js.t Lwt.t

    val select : ?use_capture:bool -> #Dom_html.eventTarget Js.t -> Dom_html.event Js.t Lwt.t

    val mousewheel : ?use_capture:bool ->
           #Dom_html.eventTarget Js.t -> (Dom_html.mouseEvent Js.t * (int * int)) Lwt.t

This function returns the event, together with the numbers of ticks the mouse wheel moved. Positive means down or right. This interface is compatible with all (recent) browsers.

    val touchstart : ?use_capture:bool ->
           #Dom_html.eventTarget Js.t -> Dom_html.touchEvent Js.t Lwt.t

    val touchmove : ?use_capture:bool ->
           #Dom_html.eventTarget Js.t -> Dom_html.touchEvent Js.t Lwt.t

    val touchend : ?use_capture:bool ->
           #Dom_html.eventTarget Js.t -> Dom_html.touchEvent Js.t Lwt.t

    val touchcancel : ?use_capture:bool ->
           #Dom_html.eventTarget Js.t -> Dom_html.touchEvent Js.t Lwt.t

    val transitionend : #Dom_html.eventTarget Js.t -> unit Lwt.t

Returns when a CSS transition terminates on the element.

    val load : ?use_capture:bool -> #Dom_html.imageElement Js.t -> Dom_html.event Js.t Lwt.t

    val error : ?use_capture:bool -> #Dom_html.imageElement Js.t -> Dom_html.event Js.t Lwt.t

    val abort : ?use_capture:bool -> #Dom_html.imageElement Js.t -> Dom_html.event Js.t Lwt.t

    val clicks : ?cancel_handler:bool ->
           ?use_capture:bool ->
           #Dom_html.eventTarget Js.t ->
           (Dom_html.mouseEvent Js.t -> unit Lwt.t -> unit Lwt.t) -> unit Lwt.t

    val dblclicks : ?cancel_handler:bool ->
           ?use_capture:bool ->
           #Dom_html.eventTarget Js.t ->
           (Dom_html.mouseEvent Js.t -> unit Lwt.t -> unit Lwt.t) -> unit Lwt.t

    val mousedowns : ?cancel_handler:bool ->
           ?use_capture:bool ->
           #Dom_html.eventTarget Js.t ->
           (Dom_html.mouseEvent Js.t -> unit Lwt.t -> unit Lwt.t) -> unit Lwt.t

    val mouseups : ?cancel_handler:bool ->
           ?use_capture:bool ->
           #Dom_html.eventTarget Js.t ->
           (Dom_html.mouseEvent Js.t -> unit Lwt.t -> unit Lwt.t) -> unit Lwt.t

    val mouseovers : ?cancel_handler:bool ->
           ?use_capture:bool ->
           #Dom_html.eventTarget Js.t ->
           (Dom_html.mouseEvent Js.t -> unit Lwt.t -> unit Lwt.t) -> unit Lwt.t

    val mousemoves : ?cancel_handler:bool ->
           ?use_capture:bool ->
           #Dom_html.eventTarget Js.t ->
           (Dom_html.mouseEvent Js.t -> unit Lwt.t -> unit Lwt.t) -> unit Lwt.t

    val mouseouts : ?cancel_handler:bool ->
           ?use_capture:bool ->
           #Dom_html.eventTarget Js.t ->
           (Dom_html.mouseEvent Js.t -> unit Lwt.t -> unit Lwt.t) -> unit Lwt.t

    val keypresses : ?cancel_handler:bool ->
           ?use_capture:bool ->
           #Dom_html.eventTarget Js.t ->
           (Dom_html.keyboardEvent Js.t -> unit Lwt.t -> unit Lwt.t) -> unit Lwt.t

    val keydowns : ?cancel_handler:bool ->
           ?use_capture:bool ->
           #Dom_html.eventTarget Js.t ->
           (Dom_html.keyboardEvent Js.t -> unit Lwt.t -> unit Lwt.t) -> unit Lwt.t

    val keyups : ?cancel_handler:bool ->
           ?use_capture:bool ->
           #Dom_html.eventTarget Js.t ->
           (Dom_html.keyboardEvent Js.t -> unit Lwt.t -> unit Lwt.t) -> unit Lwt.t

    val inputs : ?cancel_handler:bool ->
           ?use_capture:bool ->
           #Dom_html.eventTarget Js.t ->
           (Dom_html.event Js.t -> unit Lwt.t -> unit Lwt.t) -> unit Lwt.t

    val changes : ?cancel_handler:bool ->
           ?use_capture:bool ->
           #Dom_html.eventTarget Js.t ->
           (Dom_html.event Js.t -> unit Lwt.t -> unit Lwt.t) -> unit Lwt.t

    val dragstarts : ?cancel_handler:bool ->
           ?use_capture:bool ->
           #Dom_html.eventTarget Js.t ->
           (Dom_html.dragEvent Js.t -> unit Lwt.t -> unit Lwt.t) -> unit Lwt.t

    val dragends : ?cancel_handler:bool ->
           ?use_capture:bool ->
           #Dom_html.eventTarget Js.t ->
           (Dom_html.dragEvent Js.t -> unit Lwt.t -> unit Lwt.t) -> unit Lwt.t

    val dragenters : ?cancel_handler:bool ->
           ?use_capture:bool ->
           #Dom_html.eventTarget Js.t ->
           (Dom_html.dragEvent Js.t -> unit Lwt.t -> unit Lwt.t) -> unit Lwt.t

    val dragovers : ?cancel_handler:bool ->
           ?use_capture:bool ->
           #Dom_html.eventTarget Js.t ->
           (Dom_html.dragEvent Js.t -> unit Lwt.t -> unit Lwt.t) -> unit Lwt.t

    val dragleaves : ?cancel_handler:bool ->
           ?use_capture:bool ->
           #Dom_html.eventTarget Js.t ->
           (Dom_html.dragEvent Js.t -> unit Lwt.t -> unit Lwt.t) -> unit Lwt.t

    val drags : ?cancel_handler:bool ->
           ?use_capture:bool ->
           #Dom_html.eventTarget Js.t ->
           (Dom_html.dragEvent Js.t -> unit Lwt.t -> unit Lwt.t) -> unit Lwt.t

    val drops : ?cancel_handler:bool ->
           ?use_capture:bool ->
           #Dom_html.eventTarget Js.t ->
           (Dom_html.dragEvent Js.t -> unit Lwt.t -> unit Lwt.t) -> unit Lwt.t

    val mousewheels : ?cancel_handler:bool ->
           ?use_capture:bool ->
           #Dom_html.eventTarget Js.t ->
           (Dom_html.mouseEvent Js.t * (int * int) -> unit Lwt.t -> unit Lwt.t) ->
           unit Lwt.t

    val touchstarts : ?cancel_handler:bool ->
           ?use_capture:bool ->
           #Dom_html.eventTarget Js.t ->
           (Dom_html.touchEvent Js.t -> unit Lwt.t -> unit Lwt.t) -> unit Lwt.t

    val touchmoves : ?cancel_handler:bool ->
           ?use_capture:bool ->
           #Dom_html.eventTarget Js.t ->
           (Dom_html.touchEvent Js.t -> unit Lwt.t -> unit Lwt.t) -> unit Lwt.t

    val touchends : ?cancel_handler:bool ->
           ?use_capture:bool ->
           #Dom_html.eventTarget Js.t ->
           (Dom_html.touchEvent Js.t -> unit Lwt.t -> unit Lwt.t) -> unit Lwt.t

    val touchcancels : ?cancel_handler:bool ->
           ?use_capture:bool ->
           #Dom_html.eventTarget Js.t ->
           (Dom_html.touchEvent Js.t -> unit Lwt.t -> unit Lwt.t) -> unit Lwt.t

    val focuses : ?cancel_handler:bool ->
           ?use_capture:bool ->
           #Dom_html.eventTarget Js.t ->
           (Dom_html.event Js.t -> unit Lwt.t -> unit Lwt.t) -> unit Lwt.t

    val blurs : ?cancel_handler:bool ->
           ?use_capture:bool ->
           #Dom_html.eventTarget Js.t ->
           (Dom_html.event Js.t -> unit Lwt.t -> unit Lwt.t) -> unit Lwt.t

    val scrolls : ?cancel_handler:bool ->
           ?use_capture:bool ->
           #Dom_html.eventTarget Js.t ->
           (Dom_html.event Js.t -> unit Lwt.t -> unit Lwt.t) -> unit Lwt.t

    val submits : ?cancel_handler:bool ->
           ?use_capture:bool ->
           #Dom_html.eventTarget Js.t ->
           (Dom_html.event Js.t -> unit Lwt.t -> unit Lwt.t) -> unit Lwt.t

    val selects : ?cancel_handler:bool ->
           ?use_capture:bool ->
           #Dom_html.eventTarget Js.t ->
           (Dom_html.event Js.t -> unit Lwt.t -> unit Lwt.t) -> unit Lwt.t

    val request_animation_frame : unit -> unit Lwt.t

Returns when a repaint of the window by the browser starts. (see JS method `window.requestAnimationFrame`)

    val onload : unit -> Dom_html.event Js.t Lwt.t

Returns when the page is loaded

    val onbeforeunload : unit -> Dom_html.event Js.t Lwt.t

    val onresize : unit -> Dom_html.event Js.t Lwt.t

    val onpopstate : unit -> Dom_html.event Js.t Lwt.t

    val onhashchange : unit -> Dom_html.event Js.t Lwt.t

    val onresizes : (Dom_html.event Js.t -> unit Lwt.t -> unit Lwt.t) -> unit Lwt.t

    val onpopstates : (Dom_html.event Js.t -> unit Lwt.t -> unit Lwt.t) -> unit Lwt.t

    val onhashchanges : (Dom_html.event Js.t -> unit Lwt.t -> unit Lwt.t) -> unit Lwt.t