HookUI

HookUI is some sort of UI framework/loader for Cities: Skylines 2 (C:S2). It replaces the default UI with a UI that provides hooks for mod-authors to inject their own UI components, makes it fit in with the existing game UI easily.

Warning: This is a early version of the loader/framework, expect dragons

The framework/loadah gives you the ability of writing little pieces of UI that you can use just as UI mods, or integrate with your own mod so you don't have to focus too much on UI code.

It consists of a few parts:

• Ingame UI
  • HookUILoader - Loads actual components into the UI somehow
  • HookUIAPI - Exposes a JS API that mod authors use to "register" various UI components.
  • HookUIMenu - Shows a menu to activate/deactivate panels made by mod authors.
• Injected into game at runtime
  • HookUIMod - C# mod made for C:S2
  • HookUILib - C# library for mod authors to use to directly embed UIs with their own C# mods

Requirements

• Cities: Skylines 2 (duh)
• BepInEx-Unity.Mono-win-x64-6.0.0-be.674+82077ec

Installation (For players)

• Make sure BepInEx 6.0.0 is installed
• Download latest release from GitHub - https://github.com/Captain-Of-Coit/hookui/releases
• Extract the ZIP archive
• Place HookUI directory in BepInEx\plugins directory, within your game directory

Usage (For mod authors)

UI only (React)

UI only means you'll only provide UI on top of already existing data/methods available in the UI. No C# code can be added in this mode. Useful if you want to add your own visualizations or similar. You can access any of the data you see in the default UI, on any panel, and also trigger the same events as the built-in UI can trigger.

The example UI and built-in City Monitor is a UI Only mod.

Write your React UI component:

import React from 'react';

const HelloWorld = () => {
    const style = {
        position: "absolute",
        top: 100,
        left: 100,
        color: "white"
    }
    return <div style={style}>
        Hello World
    </div>
}

window._$hookui.registerPanel({
    id: "example.hello-world",
    name: "Hello World",
    icon: "Media/Game/Icons/Trash.svg",
    component: HelloWorld
})

Then you need to compile the code from JSX to JS, and bundle the code. This shouldn't be news to you if you've ever dealt with React + JSX before :)

npx esbuild helloworld.jsx --bundle --outfile=helloworld.transpiled.js

Then finally you need to put the file in the Cities2_Data\StreamingAssets\~UI~\HookUI\Extensions directory in your game directory and it'll get picked up automatically, as long as it ends with .js

With C# Mod

WARNING: Not implemented yet.

Follow the same steps as with a UI-only mod, except the last step of putting the transpiled file into the game directory.

Instead, you should reference the transpiled file inside your mod with the HookLib C# API, and it'll automatically be used when the mod is loaded.

HookUIFramework

Warning: Not implemented yet. Pending seeing how people use the existing native API.

The loader exposes a small API to help you do some common things, so not every UI author needs to write so much code.

• Menu Button (Toggles a MovableModal between hidden/visible)
• MovableModal
• SubscribeData
• TriggerEvent

Misc / Notes

"Scrape" list of events in the frontend

var allEvents = {}
var clear = engine.on('*', (a,b,c) => {
    if (['climate.temperature.update',
         'cityInfo.residentialLowDemand.update',
         'cityInfo.residentialMediumDemand.update',
         'cityInfo.residentialHighDemand.update',
         'cityInfo.industrialDemand.update',
         'cityInfo.commercialDemand.update',
         // Other common but annoying events that happen, that we already know about
         "time.ticks.update",
         "input.setActionPriority",
         "cityInfo.happinessFactors.update"

    ].includes(a)) {
        return
    }
    allEvents[a] = a
    console.log(a,b,c)
})

Click around in the UI after running this to trigger calls to capture, then finally execute copy(JSON.stringify(Object.keys(allEvents), null, 2)) to get a JS array of all found events copied into your clipboard.

"Scrape" interactive triggers

function newEngineTrigger() {
    const args = arguments
    if (!["input.setActionPriority"].includes(args[0])) {
        console.log('trigger', args)
    }
    window.engine._oldTrigger.apply(this, args)
}
window.engine._oldTrigger = window.engine.trigger
window.engine.trigger = newEngineTrigger
// To undo:
window.engine.trigger = window.engine._oldTrigger

Basic vanilla example

var myElement = document.createElement('div')
myElement.style.left = "300px"
myElement.style.top = "300px"
myElement.style.position = "relative"
myElement.style.color = "white"

var myLabel = document.createElement('span')
var myValue = document.createElement('span')

myLabel.innerHTML = 'Electricity'
myValue.innerHTML = 'N/A'

myElement.appendChild(myLabel)
myElement.appendChild(myValue)

document.body.appendChild(myElement)

// Subscription
var clear = engine.on('electricityInfo.electricityAvailability.update', (data) => {
    console.log(data)
    myValue.innerHTML = data.current.toString()
})
engine.trigger('electricityInfo.electricityAvailability.subscribe')
// later, unsubscribe
engine.trigger('electricityInfo.electricityAvailability.unsubscribe')