# Defold Druid UI Library

# Creating custom components

## Overview

Druid allows you to create your custom components from druid basic components or other custom components.

Every component is the children of Basic Druid component. Read the [basic component API here].(https://insality.github.io/druid/modules/component.html), Methods of basic components you can call via self:{method_name}

## Custom components

Basic custom component template looks like this:

    local const = require("druid.const")
    local component = require("druid.component")

    local M = component.create("my_component")

    -- Component constructor
    function M.init(self, ...)
    end

    -- Call only if exist interest: const.ON_UPDATE
    function M.update(self, dt)
    end

    -- Call only if exist interest: const.ON_INPUT or const.ON_INPUT_HIGH
    function M.on_input(self, action_id, action)
    end

    -- Call on component creation and on component:set_style() function
    function M.on_style_change(self, style)
    end

    -- Call only if exist interest: const.ON_MESSAGE
    function M.on_message(self, message_id, message, sender)
    end

    -- Call only if component with ON_ANGUAGECHANinterest
    function M.on_anguagechanself)
    end

    -- Call only if component with ON_LAYOUT_CHANGE interest
    function M.on_layout_change(self)
    end

    -- Call, if input was capturing before this component
    -- Example: scroll is start scrolling, so you need unhover button
    function M.on_input_interrupt(self)
    end

    -- Call, if game lost focus. Need ON_FOCUS_LOST intereset
    function M.on_focus_lost(self)
    end

    -- Call, if game gained focus. Need ON_FOCUS_GAINED intereset
    function M.on_focus_gained(self)
    end

    -- Call on component remove or on druid:final
    function M.on_remove(self)
    end

    return M

Add your custom component to druid via druid.register

    local druid = require("druid.druid")
    local my_component = require("my.amazing.component")

    function init(self)
        druid.register("my_component", my_component)
    end

Registering make new function with "new{componentname}". In our example it will be: `druid:new_my_component()`.

Or you can create component without registering with `druid:create(my_component_module)`

As component registered, you can create your component with next code:

    local druid = require("druid.druid")
    local my_component = require("my.amazing.component")

    function init(self)
        self.druid = druid.new(self)

        local my_component = self.druid:new_my_component(...)
        -- or --
     local my_component = self.druid:create(my_component, ...)
    end

### Interest

Interest - is a way to indicate what events your component will respond to. There is next interests in druid: - ON_MESSAGE - component will receive messages from on_message

- ON_UPDATE - component will be updated from update

- ONINPUTHIGH - component will receive input from oninput, before other components with ONINPUT

- ON_INPUT - component will receive input from oninput, after other components with ONINPUT_HIGH

- ONLANGUAGECHANGE - will call onlanguagechange function on language change trigger

- ONLAYOUTCHANGE will call onlayoutchange function on layout change trigger

- ONFOCUSLOST will call onfocustlost function in on focus lost event. You need to pass window_callback to global druid:on_window_callback

- ONFOCUSGAINED will call onfocustgained function in on focus gained event. You need to pass window_callback to global druid:on_window_callback

## Best practice on custom components

On each component recommended describe component scheme in next way:

    -- Component module
    local component = require("druid.component")

    local M = component.create("your_component")

    local SCHEME = {
        ROOT = "root",
        ITEM = "item",
        TITLE = "title"
    }

    function M.init(self, template_name, node_table)
        -- If component use template, setup it:
     self:set_template(template_name)

        -- If component was cloned with gui.clone_tree, pass his nodes
     self:set_nodes(node_table)

        -- helper can get node from gui/template/table
     local root = self:get_node(SCHEME.ROOT)

        -- This component can spawn another druid components:
     local druid = self:get_druid()

        -- Button self on callback is self of _this_ component
     local button = druid:new_button(...)
    end

## Power of using templates

You can use one component, but creating and customizing templates for them. Templates only requires to match the component scheme.

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