This package aims at handling all kinds of pointer events in elm. To be more specific, this means:
MouseEvent: standard mouse events
WheelEvent: standard wheel events
DragEvent: partial support of drag events
TouchEvent: standard touch events
PointerEvent: new pointer events
If you are looking for only one standard kind of interaction (mouse or touch),
I recommend that you use the
If however, you are designing a multi-device (desktop/tablet/mobile/...) experience,
I recommend that you use the
Pointer events are a unified interface for similar input devices (mouse, pen, touch, ...). Since maintaining both mouse and touch events for compatibility is really cumbersome, using a unified pointer events interface is a relief.
Beware though, that the pointer API is not well supported by all browsers. Firefox < 59 and Safari do not natively support pointer events. So I strongly recommend to use this package in pair with the elm-pep polyfill for compatibility with major browsers.
Pointer modules have very similar API
so I will use
Mouse as an example.
Let's say you want the coordinates of a mouse down event relative to the DOM
element that triggered it.
of the mouse event.
Using this module, these are similarly provided by the
of a mouse
import Mouse -- ... type Msg = MouseDownAt ( Float, Float ) view = div [Mouse.onDown (\event -> MouseDownAt event.offsetPos)] [text "click here"]
If you are using the
it is recommended that you deactivate
to disable browsers scroll/pinch/... touch behaviors.
Also, if you are designing some kind of drawing application, you want to be able to keep track of a pointer that leave the drawing area to know if the pointer went up. This is possible using what is called pointer capture. The example below demonstrates how to do this.
div [ Pointer.onDown ... , Pointer.onMove ... , Pointer.onUp ... -- no touch-action , Html.Attributes.style [ ( "touch-action", "none" ) ] -- pointer capture hack to continue "globally" the event anywhere on document , attribute "onpointerdown" "event.target.setPointerCapture(event.pointerId);" ] [ -- the drawing area ]
Multi-touch interactions can be managed using the
In case you only want to handle single touch interactions,
you could do something like below:
import Touch -- ... type Msg = StartAt ( Float, Float ) | MoveAt ( Float, Float ) | EndAt ( Float, Float ) view = div [ Touch.onStart (StartAt << touchCoordinates) , Touch.onMove (MoveAt << touchCoordinates) , Touch.onEnd (EndAt << touchCoordinates) ] [text "touch here"] touchCoordinates : Touch.Event -> ( Float, Float ) touchCoordinates touchEvent = List.head touchEvent.changedTouches |> Maybe.map .clientPos |> Maybe.withDefault ( 0, 0 )
You can manage
Wheel events with the corresponding module.
Since it is an extension to the
Mouse module all mouse inherited properties
are also available in the attribute
To simply check for wheel rolling up or down you could do something like below:
import Wheel -- ... type Msg = Scrolling Float view = div [Wheel.onWheel (\event -> Scrolling event.deltaY)] [text "scroll here"]
However, most of the time we just need to be able to drop some files
from the file system to the web page.
By providing the dragover, and drop events, this module enables such use case.
Of course, the file retrieved in the form of a
Json.Decode.Value would still
have to be sent through ports if further processing is needed
that cannot be done directly in elm using the
Minimalist working examples are available for each module in the
To test one example,
cd into one of them and compile the elm file with the command:
elm-make Main.elm --output Main.js
Then use any static http server like:
$ python3 -m http.server 8888
And open your browser at localhost:8888
to load the
If you are interested in contributing in any way (feedback, bug report, implementation of new functionality, ...) don't hesitate to reach out on slack (user @mattpiz) and/or open an issue. Discussion is the best way to start any contribution.
The package documentation is available on the elm package website.
This Source Code Form is subject to the terms of the Mozilla Public License,v. 2.0. If a copy of the MPL was not distributed with this file, You can obtain one at https://mozilla.org/MPL/2.0/.