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local lgi = require("lgi")
local GObject = lgi.require("GObject", "2.0")
---@class Binding
---@field emitter table | Variable | userdata
---@field property? string
---@field transform_fn function
---@overload fun(emitter: table | userdata, property?: string): Binding
local Binding = {}
Binding.__index = Binding
---@param emitter table | Variable | userdata
---@param property? string
---@return Binding
function Binding.new(emitter, property)
return setmetatable({
emitter = emitter,
property = property,
transform_fn = function(v)
return v
end,
}, Binding)
end
function Binding:__tostring()
local str = "Binding<" .. tostring(self.emitter)
if self.property ~= nil then
str = str .. ", " .. self.property
end
return str .. ">"
end
---@return any
function Binding:get()
if self.property ~= nil and GObject.Object:is_type_of(self.emitter) then
return self.transform_fn(self.emitter[self.property])
elseif type(self.emitter.get) == "function" then
return self.transform_fn(self.emitter:get())
else
error("can not get: Not a GObject or a Variable " + self)
end
end
---@param transform fun(value: any): any
---@return Binding
function Binding:as(transform)
local b = Binding.new(self.emitter, self.property)
b.transform_fn = function(v)
return transform(self.transform_fn(v))
end
return b
end
---@param callback fun(value: any)
---@return function
function Binding:subscribe(callback)
if self.property ~= nil and GObject.Object:is_type_of(self.emitter) then
local id = self.emitter.on_notify:connect(function()
callback(self:get())
end, self.property, false)
return function()
GObject.signal_handler_disconnect(self.emitter, id)
end
elseif type(self.emitter.subscribe) == "function" then
return self.emitter:subscribe(function()
callback(self:get())
end)
else
error("can not subscribe: Not a GObject or a Variable " + self)
end
end
return setmetatable(Binding, {
__call = function(_, emitter, prop)
return Binding.new(emitter, prop)
end,
})
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