Terminal.Gui.Elmish

An elmish wrapper around Miguel de Icaza's 'Gui.cs' https://github.com/migueldeicaza/gui.cs including a Feliz-like like view DSL.

Major Changes

I decided to rework the DSL to a Feliz-style. Thank you Zaid Ajaj (https://github.com/Zaid-Ajaj/Feliz) for that awesome idea! You can leverage now more the Intellisense of your IDE.
I also introduced a diffing mechanism, so that the elements are not recreated on every cycle. I try actually to update the current elements.

This can be end up sometimes in some weird behavior or exceptions. I try to find all the quirks, but help me out and open an issue if you find something.

Documentation

It's missing again!

Almost all properties from the View-Elements should be available. Some events I extended. For example the Toggled-Event from a checkbox returns the old value in the event.
I mapped the event to return both.

Example

In the examples you find the old project, which I converted to the new DSL

Usage:

Program.mkProgram init update view  
|> Program.run
    

Some fable-elmish DSL:

module Counter

open Terminal.Gui
open Terminal.Gui.Elmish
open System

type Model = {
    Counter:int
    IsSpinning: bool
}

type Msg =
    | Increment
    | Decrement
    | Reset
    | StartSpin
    | StopSpin
    | Spinned

let init () : Model * Cmd<Msg> =
    let model = {
        Counter = 0
        IsSpinning = false
    }
    model, Cmd.none


module Commands =
    let startSpinning isSpinning =
        fun dispatch ->
            async {
                do! Async.Sleep 20
                if isSpinning then
                    dispatch Increment
                    dispatch Spinned
            }
            |> Async.StartImmediate
        |> Cmd.ofSub

let update (msg:Msg) (model:Model) =
    match msg with
    | Increment ->
        {model with Counter = model.Counter + 1}, Cmd.none
    | Decrement ->
        {model with Counter = model.Counter - 1}, Cmd.none
    | Reset ->
        {model with Counter = 0}, Cmd.none
    | StartSpin ->
        {model with IsSpinning = true}, Commands.startSpinning true
    | StopSpin ->
        {model with IsSpinning = false}, Cmd.none
    | Spinned ->
        model, Commands.startSpinning model.IsSpinning
        


let view (model:Model) (dispatch:Msg->unit) =
    View.page [
        page.menuBar [
            menubar.menus [
                menu.menuBarItem [
                    menu.prop.title "Menu 1"
                    menu.prop.children [
                        menu.submenuItem [
                            menu.prop.title "Sub Menu 1"
                            menu.prop.children [
                                menu.menuItem ("Sub Item 1", (fun () -> System.Diagnostics.Debug.WriteLine($"Sub menu 1 triggered")))
                                menu.menuItem [
                                    menu.prop.title "Sub Item 2"
                                    menu.item.action (fun () -> System.Diagnostics.Debug.WriteLine($"Sub menu 2 triggered"))
                                    menu.item.itemstyle.check
                                    menu.item.isChecked true
                                ]
                            ]
                        ]
                    ]
                ]
            ]
        ]
        prop.children [
            View.label [
                prop.position.x.center
                prop.position.y.at 1
                prop.textAlignment.centered
                prop.color (Color.BrightYellow, Color.Green)
                label.text "'F#ncy' Counter!"
            ] 

            View.button [
                prop.position.x.center
                prop.position.y.at 5
                label.text "Up"
                button.onClick (fun () -> dispatch Increment)
            ] 

            View.label [
                let c = (model.Counter |> float) / 100.0
                let x = (16.0 * Math.Cos(c)) |> int 
                let y = (8.0 * Math.Sin(c)) |> int

                prop.position.x.at (x + 20)
                prop.position.y.at (y + 10)
                prop.textAlignment.centered
                prop.color (Color.Magenta, Color.BrightYellow)
                label.text $"The Count of 'Fancyness' is {model.Counter}"
            ] 


            View.button [
                prop.position.x.center
                prop.position.y.at 7
                label.text "Down"
                button.onClick (fun () -> dispatch Decrement)
            ] 

            View.button [
                prop.position.x.center
                prop.position.y.at 9
                label.text "Start Spinning"
                button.onClick (fun () -> dispatch StartSpin)
            ] 

            View.button [
                prop.position.x.center
                prop.position.y.at 11
                label.text "Stop Spinning"
                button.onClick (fun () -> dispatch StopSpin)
            ] 

            View.button [
                prop.position.x.center
                prop.position.y.at 13
                label.text "Reset"
                button.onClick (fun () -> dispatch Reset)
            ]
        ]
    ]

Install via Nuget:

https://www.nuget.org/packages/Terminal.Gui.Elmish

dotnet add package Terminal.Gui.Elmish

Referencing the underlying Element

You can reference the underlying element. Also use this to influcence further setting when the element is created!

use prop.ref (fun view -> ...)

View.button [
    prop.position.x.center
    prop.position.y.at 13
    label.text "Reset"
    button.onClick (fun () -> dispatch Reset)
    prop.ref (fun view -> myButtonRef <- (view :?> Terminal.Gui.Button).xxxx // do your stuff here)
]

A lot of Thanks to Miguel de Icaza. Nice Project!.