# Plugin development

In this guide you'll learn the fundamental bits to create your own PRESENTA Lib plugin.

# What is a PRESENTA Lib Plugin?

It's a javascript function that exploits the PRESENTA Lib APIs in order to add further capabilities. To give a glimpse, this is a valid PRESENTA Lib plugin (a Block plugin) that does nothing but a console.log:

// myPlugin.js
function myPlugin(){
  console.log('Hello empty Block!')
}

Presenta.addBlock('myplug', myPlugin)

Put the above code in a .js file and load it after the PRESENTA Lib script tag. Then, here how to use it in a PRESENTA config:

// main.js
const config = {
  scenes:[{
    blocks:[{
      type:'myplug'
    }]
  }]
}

new Presenta('#app', config)

You can see the same example in this Codepen(opens new window) , open the console to see if it works.

The equivalent ES6 version of the same plugin needs to support the module import capability of a js bundler:

// myPlugin.js
function myPlugin(){
  console.log('Hello empty Block!')
}

export default myPlugin

myPlugin.install = Presenta => {
  Presenta.addBlock('myplug', myPlugin)
}

This is because when you include PRESENTA Lib and their plugins in ES6, you need to do initialize them explicitly, such as:

// main.js
import * as Presenta from '@presenta/lib'
import MyPlugin from './myPlugin.js'

Presenta.use(MyPlugin)

# Types of Plugin

It's important to understand that PRESENTA Lib has three types of plugin:

  • Blocks
  • Modules
  • Controllers

A Block renders a content. A scene can contains one or more independent blocks. When you need to render a content in a specific way, you need a Block.

A Module adds elements and functionalities at scene level. When you need to extend a scene, causing something that happen in the scene context only, you need a Module.

A Controller adds elements and functionalities at presentation level. When you need to add something that lives in the whole presentation document, you need a Controller.

# Create your first Block

In a Block plugin you can exploit two arguments:

  • the wrapper element where you can put whatever you want
  • the config chunk of the block, provided by the end user
// add an H1 tag with a user defined content
function myH1(blockElement, blockConfig){
  const h1 = document.createElement('h1')
  const name = blockConfig.name || 'Unknown'
  h1.innerText = name
  blockElement.appendChild(h1)
}

Presenta.addBlock('myH1', myH1) // this is specific for Block init

So, the config requires:

const config = {
  scenes:[{
    blocks:[{
      type:'myH1',
      name:'John Doe'
    }]
  }]
}

new Presenta('#app', config)

Here the above example up and running in Codepen(opens new window) .

# Clean-up all-the-things

If your Block contains something that needs to be disposed when the block is removed, here the method you have to implement:

function myH1(blockElement, blockConfig){
  // ...
  
  this.destroy = () => {
    // remove, kill, stop, cleanup, then the block will be removed
  }
}

# Use a Promise if you need it

A Block can return a Promise if internally it needs to performe some async stuff. PRESENTA Lib will wait for all block resolutions before render the scene.

TIP

If you want to use the same dev setup of the official plugins, here the block starterkit(opens new window) .

# Create your first Module

In a Module plugin you can exploit three arguments:

  • the wrapper element of the scene element where you can add something overimposed on all the blocks
  • the config chunk of the module, provided by the end user
  • the config chunk of the whole scene, provided by the end user
// add a info strip that shows how many blocks there are in the current scene
function myNumBlocks(sceneElement, modConfig, sceneConfig){
  const num = sceneConfig.blocks.length
  
  const el = document.createElement('div')
  el.innerText = 'There are ' + num + ' blocks in this scene'
  el.classList.add('strip')
  
  sceneElement.appendChild(el)
}

Presenta.addModule('myNumBlocks', myNumBlocks) // this is specific for Module init

And here the config to activate the plugin:

const config = {
  modules:{
    myNumBlocks:true
  },
  scenes:[{
    blocks:[{
      type:'text',
      text:'Hello 1'
    }]
  }]
}

new Presenta('#app', config)

Here the above example up and running in Codepen(opens new window) .

# Use a Promise if you need it

A Module can return a Promise if internally it needs to performe some async stuff. PRESENTA Lib will wait for all module resolutions before render the scene.

TIP

If you want to use the same dev setup of the official plugins, here the module starterkit(opens new window) .

# Create your first Controller

In a Controller plugin you can exploit four arguments:

  • the wrapper element that holds all the controllers in a presentation
  • the Router object to listen for its events and/or call its public methods as well
  • the config chunk of the controller itself, provided by the end user
  • the whole presentation config, provided by the end user, that init the whole presentation
// add an element and move it on each scene change
function myMovingEl(routerElement, router, ctrlConfig, projectConfig){
  
  const dot = document.createElement('div')
  dot.classList.add('dot')
  routerElement.appendChild(dot)
  
  router.on('indexChanged', e => {
    
    const comp = routerElement.getBoundingClientRect()
    
    const x = Math.random() * comp.width
    const y = Math.random() * comp.height
    
    dot.style.transform = `translate(${x}%, ${y}%)`
  })
}

Presenta.addController('myMovingEl', myMovingEl) // this is specific for Controller init

And here the config to activate the plugin:

const config = {
  controllers:{
    myMovingEl:true
  },
  scenes:[{
    blocks:[{
      type:'text',
      text:'Hello 1'
    }]
  }]
}

new Presenta('#app', config)

Here the above example up and running in Codepen(opens new window) .

# Use a Promise if you need it

A Controller can return a Promise if internally it needs to performe some async stuff. PRESENTA Lib will wait for all controller resolutions before start the presentation.

TIP

If you want to use the same dev setup of the official plugins, here the controller starterkit(opens new window) .

# Not enough?

You can learn more from: