Elmでマウスの右クリックを検知するにはどうすれば？と思って調べた際のメモ。

mpizenberg/elm-pointer-events を使うのが楽そう。

左クリックor右クリックをボタンのテキストに表示するサンプルコード

module Main exposing (main)

import Browser
import Html exposing (Html, button, div, text)
import Html.Events.Extra.Mouse as Mouse

type alias Model = { buttonText : String }

type Msg = LeftClick | RightClick

initialModel : Model
initialModel =
    { buttonText = "Clicked: -" }

update : Msg -> Model -> Model
update msg model =
    case msg of
        LeftClick ->
            { model | buttonText = "Clicked: Left" }

        RightClick ->
            { model | buttonText = "Clicked: Right" }

view : Model -> Html Msg
view model =
    div []
        [ button
            [ Mouse.onClick (\_ -> LeftClick)
            , Mouse.onContextMenu (\_ -> RightClick)
            ]
            [ text model.buttonText ]
        ]

main : Program () Model Msg
main =
    Browser.sandbox
        { init = initialModel
        , view = view
        , update = update
        }

実際のアプリ(Ellie)

2022.12.10 追記

@ababup1192 さんから Html.Events.custom でいけますよとのこと。

折角なので実装してみましょう。

Html.Events.custom版

module Main exposing (main)

import Browser
import Html exposing (Attribute, Html, button, div, text)
import Html.Events as Events
import Json.Decode as JD

-- (略)

view : Model -> Html Msg
view model =
    div []
        [ button
            [ Events.onClick LeftClick
            , Events.custom "contextmenu" <|
                JD.succeed
                    { message = RightClick
                    , stopPropagation = True
                    , preventDefault = True
                    }
            ]
            [ text model.buttonText ]
        ]

-- (略)

実際のアプリ(Ellie)

OK👍