Corona Invalidation Sample 2 of 2: AutoSizeText.lua. Show's using invalidation to cache all text field changes once per frame.

AutoSizeText.lua

require "Component"
AutoSizeText = {}

function AutoSizeText:new()

  local view = Component:new()
	view._text = nil
	view.textDirty = false

	view._rgba = {255, 255, 255, 255}
	view.rgbaDirty = false

	view._fontSize = 18
	view.fontSizeDirty = false

	view._width = nil
	view._height = nil
	view._autoSize = false
	view.autoSizeDirty = false

	view._bold = false

	

	function view:createChildren()
		self:setText("")
	end

	function view:getText()
		return self._text
	end

	function view:setText(str, bypass)
		if self._text == str and bypass ~= true then
			return true
		end

		self._text = str
		self.textDirty = true
		self:invalidateProperties()
	end

	function view:commitProperties()
		if self.textDirty == true then
			self.textDirty = false
			if self.field then
				self.field:removeSelf()
				self.field = nil
			end

			local field
			local fontName
			if self._bold == false then
				fontName = native.systemFont
			else
				fontName = native.systemFontBold
			end
			
			if self._autoSize == false then
				field = display.newText(str, 0, 0, fontName, self._fontSize)
			else
				field = display.newText(str, 0, 0, self._width, self._height, fontName, self._fontSize)
			end

			field:setReferencePoint(display.TopLeftReferencePoint)
			field:setTextColor(unpack(self._rgba))
			self.field = field
			self:insert(field)
		end

		if self.rgbaDirty == true then
			self.field:setTextColor(r, g, b, alpha)
		end
	end

	function view:setTextColor(r, g, b, alpha)
		if alpha == nil then
			alpha = 255
		end
		self._rgba = {r, g, b, alpha}
		self.rgbaDirty = true
		self:invalidateProperties()
	end

	function view:setFontSize(size)
		self._fontSize = size
		self.fontSizeDirty = true
		self:invalidateProperties()
	end

	function view:setSize(w, h)
		local dirty = false
		if self._width ~= w or self._height ~= h then
			dirty = true
		end
		self._width = w
		self._height = h
		if dirty then
			self:setText(self._text, true)
		end
	end

	function view:setAutoSize(val)
		if value ~= val then
			self._autoSize = val
			self:setText(self._text, true)
		end
	end

	function view:setBold(bold)
		if value ~= val then
			self._bold = bold
			self:setText(self._text, true)
		end
	end

	view:init()

	return view

end

return AutoSizeText