Module Useri_jsoo.Key

module Key: sig .. end
User keyboard.

Consult information about getting keyboard events and limitations.

Keyboard event target

val event_target : unit -> Dom_html.eventTarget Js.t option
source () is the event target used for keyboard events.
val set_event_target : Dom_html.eventTarget Js.t option -> unit
set_event_target target sets the event target to target. If None the canvas of the surface will be used.

Warning. This may be removed in the future.

Important. You need to set the event target before calling Useri.App.init. And a Useri.App.release sets the event target back to None.

Keyboard event capture

val key_capture : unit -> -> bool
key_capture () is the function that determines whether key events related to a key are captured by Useri (i.e prevent default action and stop propagation). The initial function never captures.
val set_key_capture : ( -> bool) -> unit
set_capture_key capture sets the function returned by Useri_jsoo.Key.key_capture.

Getting keyboard events

There are a few things you need to make sure are setup in order to get the keyboard events.

First to get events directly on the HTML canvas associated to the surface it needs to have a tabindex attribute. If Useri creates the canvas it sets one, but don't forget to set one if you provide the canvas at initialization time through an handle. Events will only be generated once the user has focused the canvas in one way or another (e.g. by clicking on it). The latter operation may introduce a selection box around the canvas, the selection box can be hidden by applying the CSS rule { outline: none; } on the canvas.

You can also choose to get the keyboard events from another event target using the Useri_jsoo.Key.set_event_target before initializing the application. For example using the Dom_html.window will prevent the user from having to focus in order for you to get keyboard events.

By default keyboard event will not stop propagating and will perform their default action. You can prevent that to occur on certain keys by registering a function with Useri_jsoo.Key.set_key_capture. Note that in certain browsers (e.g. Safari) it is not possible to prevent the default action of certain key strokes.

Fullscreen. Note that in general in fullscreen mode you may not get keyboard events or only some of them for security reasons.


The following limitations exist (they may be lifted in the future).