ScreenJS

Download: CurseForge

The custom ContainerMenu event is a startup event.

Custom Container menus are created in a startup script. They cannot be reloaded without restarting the game. The event is not cancellable.

for block entities made with beJS:

StartupEvents.registry('menu', event => {
    event.create('example_block' /*name has to be same as BlockEntity's id*/, 'block_entity')
        .addSlot(-10, -10) // adds a slot into this x,y position on the texture
        .addSlot(10, 200)
        .loop(builder /*this builder*/=> {
            for(let x = 0; x < 9; x++) {
                for (let y = 0; y < 4; y++) {
                    builder.addSlot(x * 18 /*<- the width of a slot, remember to add this*/, y * 18)
                }
            }
        })
        .addOutputSlot(118, 118) // adds a slot you can't put an item into, but can pull an item from
        .playerInventoryY(100) // marks the start of the player's inventory on the texture
        .tintColor(0x00FF00FF) // a color to tint the whole inventory texture, in hexadecimal [r, g, b, a]
})

for any block: 

StartupEvents.registry('menu', event => {
    event.create('grass_block' /*name can be anything*/, 'block')
        /*default parameter set*/
        .setBlock('minecraft:grass_block') // the block that should open this GUI on right-click
})

for entities: 

StartupEvents.registry('menu', event => {
    event.create('snow_golem' /*name can be anything*/, 'entity')
        /*default parameter set*/
        .setEntity('minecraft:snow_golem') // the enity type that should open this GUI on right-click
})

and lastly, for completely separate 'basic' GUIs:

currently nothing can access these!

StartupEvents.registry('menu', event => {
    event.create('snow_golem' /*name can be anything*/)
        /*default parameter set*/
})

valid menu types:

• basic (this is the default)
• block_entity
• block
• entity

methods the menu builder supports:

• addSlot(x, y)
• addOutputSlot(x, y)
• loop()
• tintColor(color)
• drawable(screenX, screenY, textureX, textureY, u, v, textureLocation)
• progressDrawable(x, y, textureX, textureY, textureWidth, textureHeight, textureLocation, direction, type)
• fluidDrawable(x, y, textureX, textureY, textureWidth, textureHeight, textureLocation, direction, tankIndex)
• backroundTexture(texture, x, y, u ,v)
• quickMoveFunc((player, slotIndex, menu) => ... return item)
• validityFunc((player, pos) => ... return boolean)
• disablePlayerInventory()
  
• playerInventoryY(yPos)