main.lua

local app = sheets.Application()

local button1 = app.screen + sheets.Button( 0, 0, 20, 5, "Hello world!" )
local right = app.screen + sheets.Button( 0, 1, 7, 3, "Right" )

local old = { [button1] = {}, [right] = {} }

right:set_ID "right"

old[button1].width = button1.set_width
old[button1].x = button1.set_x
old[right].width = right.set_width
old[right].x = right.set_x

local function parse_val( self, value )
	local refs = {}
	local props = {}

	if type( value ) == "number" then
		return function() return value end, refs, props
	end

	for a, b in value:gmatch "(%w+)%.(%w+)" do
		if a == "self" then
			refs[#refs + 1] = self
		else
			refs[#refs + 1] = app:query( a )[1]
		end
		props[#props + 1] = b
	end

	local s = value:gsub( "(%w+)%.(%w+)", function( a, b )
		if a == "self" then
			return "self." .. b
		else
			return ("app:query '#%s' [1].%s"):format( a, b )
		end
	end )

	return assert( loadstring( "local app, self = ... return function() return " .. s .. " end", "script" ) )( app, self ), refs, props
end

local function setter( prop )
	return function( self, value )
		self.values:respawn( prop )

		local f, refs, props = parse_val( self, value )

		for i = 1, #refs do
			local object = refs[i]
			local property = props[i]

			object.values:subscribe( property, self.values.lifetimes[prop], function()
				old[self][prop]( self, f() )
				self.values:trigger( prop )
			end )
		end

		self["raw_" .. prop] = value
		old[self][prop]( self, f() )
		self.values:trigger( prop )
	end
end

button1.values:add( "width", "integer", 0, setter "width" )
button1.values:add( "x", "integer", 0, setter "x" )
right.values:add( "width", "integer", 0, setter "width" )
right.values:add( "x", "integer", 0, setter "x" )

right:set_x "51 - self.width + 1"
right:set_width "#self.text + 2"

button1:set_x "5"
button1:set_width "right.x - self.x"

local b = false

function button1:on_click()
	if not b then
		self:animate_x( 20, 0.4 )
		b = true
	else
		app:stop()
	end
end

function right:on_click()
	self:animate_width( 15, 0.4 )
end

app:run()