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init_handler (short: ini)

The handler receives self as its implicit parameter (object-oriented style). This handler is available on all element types and runs once when the element or page is initialized.

Purpose

The init handler is used to:

  • Set up initial element state
  • Configure default values
  • Initialize custom variables on self
  • Set up LED colors for the initial state
  • Register callbacks (e.g., midirx_cb, eventrx_cb)

Available Methods via self

The init handler has access to all methods of its parent element type:

  • For encoders: all encoder parameters (eva, emo, etc.) and button parameters
  • For buttons: all button parameters (bva, bst, etc.)
  • For potmeters: all potmeter parameters (pva, pmo, etc.)
  • For endless: all endless parameters (epva, epmo, etc.) and button parameters
  • For system: page functions (gpn, gpc, gpl, etc.)
  • For LCD: screen parameters and drawing functions

General functions (always available)

Short Human Name Description
ind element_index Element index
glc led_color LED color
glp led_phase LED phase
gms midi_send MIDI send
gtt timer_start Timer start
gtp timer_stop Timer stop
get event_trigger Event trigger
gen element_name Get element name
gsen element_name_set Set element name

Default Action Strings

The default init handlers are placeholder comments for user code:

Element Default Action String
Encoder --[[Encoder Init]]
Button --[[Button Init]]
Potmeter --[[Potmeter Init]]
Endless --[[Endless Init]]
System --[[page init]]
LCD Complex initialization (see below)

LCD Init Example

The LCD init handler sets up display variables and callbacks:

glsb(255)  -- set backlight
pi,s,c = math.pi, 64, {{0,0,0},{255,255,255},{glr(),glg(),glb()}}
self.f = 1  -- frame flag
self.v = {27,0,100}  -- value array
self.id = 'VSN1'  -- element ID string

-- Element type names
d = {[1]='Linear',[2]='Encoder',[3]='Button',[7]='Endless'}

-- Screen center and padding
xc,yc,p = 160,120,s*5/8

-- Event receive callback
self.eventrx_cb = function(self,hdr,e,v,n)
  self.v = v
  if #n==0 then n=d[e[3]]..e[2] end
  self.id = string.sub(n,1,(self:lsw()/(s/2)-1)//1)
  self.f = 1
end

-- Draw initial frame
self:ldaf(0,0,319,239,c[1])
self:ldrr(3,3,317,237,10,c[2])

Common Use Cases

Setting initial LED color

self:glc(1, {{255, 0, 0, 1}})  -- Red LED

Starting a timer

self:gtt(100)  -- Start 100ms timer

Initializing custom state

self.counter = 0
self.mode = 1

Registering MIDI receive callback

self.midirx_cb = function(self, event, header)
  -- Handle incoming MIDI
end

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