From f6fb8ad6499f00390505f16071aefc16a833377b Mon Sep 17 00:00:00 2001
From: Reuh <fildadut@reuh.eu>
Date: Fri, 27 Dec 2019 18:54:30 +0100
Subject: [PATCH] uqt.signal

---
 backend/ctrulua.lua       |  38 ++++++++-----
 backend/love.lua          |  33 ++++++++---
 init.lua                  |  22 ++------
 input/backend/ctrulua.lua |   8 +++
 input/backend/love.lua    |  50 +++++++++-------
 input/input.lua           |  55 +++++++++++-------
 scene/scene.lua           |  21 ++++++-
 signal/backend/love.lua   |  43 ++++++++++++++
 signal/init.lua           |  14 +++++
 signal/signal.can         | 116 ++++++++++++++++++++++++++++++++++++++
 timer/timer.lua           |  11 +++-
 11 files changed, 331 insertions(+), 80 deletions(-)
 create mode 100644 signal/backend/love.lua
 create mode 100644 signal/init.lua
 create mode 100644 signal/signal.can

diff --git a/backend/ctrulua.lua b/backend/ctrulua.lua
index 3ca8e6b..f24aaa5 100644
--- a/backend/ctrulua.lua
+++ b/backend/ctrulua.lua
@@ -2,18 +2,30 @@ local uqt = require((...):match("^(.-ubiquitousse)%."))
 local ctr = require("ctr")
 local gfx = require("ctr.gfx")
 
-local function checkCompat(stuffName, expectedVersion, actualVersion)
-	if actualVersion ~= expectedVersion then
-		local txt = ("Ubiquitousse ctrµLua backend was made for %s %s but %s is used!\nThings may not work as expected.")
-		            :format(stuffName, expectedVersion, actualVersion)
-		print(txt)
-		for _=0,300 do
-			gfx.start(gfx.TOP)
-				gfx.wrappedText(0, 0, txt, gfx.TOP_WIDTH)
-			gfx.stop()
-			gfx.render()
-		end
+local madeForCtr = "v1.0"
+local madeForUqt = "0.0.1"
+
+-- Check versions
+local txt = ""
+
+if ctr.version ~= madeForCtr then
+	txt = txt .. ("Ubiquitousse ctrµLua backend was made for ctrµLua %s but %s is used!\n")
+		:format(madeForCtr, uqt.version)
+end
+
+if uqt.version ~= madeForUqt then
+	txt = txt .. ("Ubiquitousse ctrµLua backend was made for Ubiquitousse %s but %s is used!\n")
+		:format(madeForUqt, uqt.version)
+end
+
+-- Show warnings
+if txt ~= "" then
+	txt = txt .. "Things may not work as expected.\n"
+	print(txt)
+	for _=0,300 do
+		gfx.start(gfx.TOP)
+			gfx.wrappedText(0, 0, txt, gfx.TOP_WIDTH)
+		gfx.stop()
+		gfx.render()
 	end
 end
-checkCompat("ctrµLua", "v1.0", ctr.version) -- not really a version, just get the latest build
-checkCompat("Ubiquitousse", "0.0.1", uqt.version)
diff --git a/backend/love.lua b/backend/love.lua
index 8754772..ef320cc 100644
--- a/backend/love.lua
+++ b/backend/love.lua
@@ -1,11 +1,30 @@
 local uqt = require((...):match("^(.-ubiquitousse)%."))
 
-local function checkCompat(stuffName, expectedVersion, actualVersion)
-	if actualVersion ~= expectedVersion then
-		local txt = ("Ubiquitousse Löve backend was made for %s %s but %s is used!\nThings may not work as expected.")
-		            :format(stuffName, expectedVersion, actualVersion)
-		print(txt)
+local madeForLove = { 11, "x", "x" }
+local madeForUqt = "0.0.1"
+
+-- Check versions
+local txt = ""
+
+local actualLove = { love.getVersion() }
+for i, v in ipairs(madeForLove) do
+	if v ~= "x" then
+		if actualLove[i] ~= v then
+			txt = txt .. ("Ubiquitousse Löve backend was made for LÖVE %s.%s.%s but %s.%s.%s is used!\n")
+				:format(madeForLove[1], madeForLove[2], madeForLove[3], actualLove[1], actualLove[2], actualLove[3])
+			break
+		end
 	end
 end
-checkCompat("Löve", "11.3.0", ("%s.%s.%s"):format(love.getVersion()))
-checkCompat("Ubiquitousse", "0.0.1", uqt.version)
+
+if uqt.version ~= madeForUqt then
+	txt = txt .. ("Ubiquitousse Löve backend was made for Ubiquitousse %s but %s is used!\n")
+		:format(madeForUqt, uqt.version)
+end
+
+-- Show warnings
+if txt ~= "" then
+	txt = txt .. "Things may not work as expected.\n"
+	print(txt)
+	love.window.showMessageBox("Compatibility warning", txt, "warning")
+end
diff --git a/init.lua b/init.lua
index 8f48c2b..6f5a7d1 100644
--- a/init.lua
+++ b/init.lua
@@ -64,33 +64,19 @@ local ubiquitousse
 ubiquitousse = {
 	--- Ubiquitousse version.
 	-- @impl ubiquitousse
-	version = "0.0.1",
-
-	--- Should be called each time the game loop is ran; will update every loaded Ubiquitousse module that needs it.
-	-- @tparam number dt time since last call, in miliseconds
-	-- @impl mixed
-	update = function(dt)
-		if ubiquitousse.timer then ubiquitousse.timer.update(dt) end
-		if ubiquitousse.scene then ubiquitousse.scene.update(dt) end
-		if ubiquitousse.input then ubiquitousse.input.update(dt) end
-	end,
-
-	--- Should be called each time the game expect a new frame to be drawn; will draw every loaded Ubiquitousse module that needs it
-	-- The screen is expected to be cleared since last frame.
-	-- @impl mixed
-	draw = function()
-		if ubiquitousse.scene then ubiquitousse.scene.draw() end
-	end
+	version = "0.0.1"
 }
 
 -- We're going to require modules requiring Ubiquitousse, so to avoid stack overflows we already register the ubiquitousse package
 package.loaded[p] = ubiquitousse
 
 -- Require external submodules
-for _, m in ipairs{"asset", "ecs", "input", "scene", "timer", "util"} do
+for _, m in ipairs{"signal", "asset", "ecs", "input", "scene", "timer", "util"} do
 	local s, t = pcall(require, p.."."..m)
 	if s then
 		ubiquitousse[m] = t
+	elseif not t:match("^module [^n]+ not found") then
+		error(t)
 	end
 end
 
diff --git a/input/backend/ctrulua.lua b/input/backend/ctrulua.lua
index 6829663..cccb8d9 100644
--- a/input/backend/ctrulua.lua
+++ b/input/backend/ctrulua.lua
@@ -1,5 +1,8 @@
 local input = require((...):match("^(.-%.)backend").."input")
 
+local loaded, signal = pcall(require, (...):match("^(.-)input").."signal")
+if not loaded then signal = nil end
+
 local gfx = require("ctr.gfx")
 local hid = require("ctr.hid")
 
@@ -266,4 +269,9 @@ input.default.pointer:bind(
 input.default.confirm:bind("key.a")
 input.default.cancel:bind("key.b")
 
+--- Register signals
+if signal then
+	signal.event:replace("update", oUpdate, input.update)
+end
+
 return input
diff --git a/input/backend/love.lua b/input/backend/love.lua
index 158547e..833f151 100644
--- a/input/backend/love.lua
+++ b/input/backend/love.lua
@@ -1,5 +1,8 @@
 local input = require((...):match("^(.-%.)backend").."input")
 
+local loaded, signal = pcall(require, (...):match("^(.-)input").."signal")
+if not loaded then signal = nil end
+
 -- Config --
 
 -- Use ScanCodes (layout independant input) instead of KeyConstants (layout dependant) for keyboard input
@@ -13,24 +16,23 @@ local displayKeyConstant = true
 love.mouse.setVisible(false)
 
 -- Button detection
--- FIXME  love callbacks do something cleaner
 local buttonsInUse = {}
 local axesInUse = {}
-function love.keypressed(key, scancode, isrepeat)
+function input.keypressed(key, scancode, isrepeat)
 	if useScancodes then key = scancode end
 	buttonsInUse["keyboard."..key] = true
 end
-function love.keyreleased(key, scancode)
+function input.keyreleased(key, scancode)
 	if useScancodes then key = scancode end
 	buttonsInUse["keyboard."..key] = nil
 end
-function love.mousepressed(x, y, button, istouch)
+function input.mousepressed(x, y, button, istouch)
 	buttonsInUse["mouse."..button] = true
 end
-function love.mousereleased(x, y, button, istouch)
+function input.mousereleased(x, y, button, istouch)
 	buttonsInUse["mouse."..button] = nil
 end
-function love.wheelmoved(x, y)
+function input.wheelmoved(x, y)
 	if y > 0 then
 		buttonsInUse["mouse.wheel.up"] = true
 	elseif y < 0 then
@@ -42,17 +44,17 @@ function love.wheelmoved(x, y)
 		buttonsInUse["mouse.wheel.left"] = true
 	end
 end
-function love.mousemoved(x, y, dx, dy)
+function input.mousemoved(x, y, dx, dy)
 	if dx ~= 0 then axesInUse["mouse.move.x"] = dx/love.graphics.getWidth() end
 	if dy ~= 0 then axesInUse["mouse.move.y"] = dy/love.graphics.getHeight() end
 end
-function love.gamepadpressed(joystick, button)
+function input.gamepadpressed(joystick, button)
 	buttonsInUse["gamepad.button."..joystick:getID().."."..button] = true
 end
-function love.gamepadreleased(joystick, button)
+function input.gamepadreleased(joystick, button)
 	buttonsInUse["gamepad.button."..joystick:getID().."."..button] = nil
 end
-function love.gamepadaxis(joystick, axis, value)
+function input.gamepadaxis(joystick, axis, value)
 	if value ~= 0 then
 		axesInUse["gamepad.axis."..joystick:getID().."."..axis] = value
 	else
@@ -61,11 +63,7 @@ function love.gamepadaxis(joystick, axis, value)
 end
 
 -- Windows size
-input.drawWidth, input.drawHeight = love.graphics.getWidth(), love.graphics.getHeight()
-function love.resize(width, height)
-	input.drawWidth = width
-	input.drawHeight = height
-end
+input.getDrawWidth, input.getDrawHeight = love.graphics.getWidth, love.graphics.getHeight
 
 -- Update
 local oUpdate = input.update
@@ -190,7 +188,7 @@ input.basicAxisDetector = function(id)
 	end
 end
 
-input.buttonsInUse = function(threshold)
+input.buttonUsed = function(threshold)
 	local r = {}
 	threshold = threshold or 0.5
 	for b in pairs(buttonsInUse) do
@@ -201,10 +199,10 @@ input.buttonsInUse = function(threshold)
 			table.insert(r, b.."%"..(v < 0 and -threshold or threshold))
 		end
 	end
-	return r
+	return unpack(r)
 end
 
-input.axesInUse = function(threshold)
+input.axisUsed = function(threshold)
 	local r = {}
 	threshold = threshold or 0.5
 	for b,v in pairs(axesInUse) do
@@ -212,7 +210,7 @@ input.axesInUse = function(threshold)
 			table.insert(r, b.."%"..threshold)
 		end
 	end
-	return r
+	return unpack(r)
 end
 
 input.buttonName = function(...)
@@ -316,4 +314,18 @@ input.default.cancel:bind(
 	"gamepad.button.1.b"
 )
 
+--- Register signals
+if signal then
+	signal.event:bind("keypressed", input.keypressed)
+	signal.event:bind("keyreleased", input.keyreleased)
+	signal.event:bind("mousepressed", input.mousepressed)
+	signal.event:bind("mousereleased", input.mousereleased)
+	signal.event:bind("wheelmoved", input.wheelmoved)
+	signal.event:bind("mousemoved", input.mousemoved)
+	signal.event:bind("gamepadpressed", input.gamepadpressed)
+	signal.event:bind("gamepadreleased", input.gamepadreleased)
+	signal.event:bind("gamepadaxis", input.gamepadaxis)
+	signal.event:replace("update", oUpdate, input.update)
+end
+
 return input
diff --git a/input/input.lua b/input/input.lua
index 0d8a988..403cc19 100644
--- a/input/input.lua
+++ b/input/input.lua
@@ -1,5 +1,8 @@
 --- ubiquitousse.input
 -- Depends on a backend.
+-- Optional dependencies: ubiquitousse.signal (to bind to update signal in signal.event)
+local loaded, signal = pcall(require, (...):match("^(.-)input").."signal")
+if not loaded then signal = nil end
 
 -- TODO: some key selection helper? Will be backend-implemented, to account for all the possible input methods.
 -- TODO: some way to list all possible input / outputs, or make the *inUse make some separation between inputs indiscutitably in use and those who are incertain.
@@ -40,8 +43,8 @@ local button_mt = {
 	-- @treturn ButtonInput this ButtonInput object
 	unbind = function(self, ...)
 		for _, d in ipairs({...}) do
-			for i, detector in ipairs(self.detectors) do
-				if detector == d then
+			for i=#self.detectors, 1, -1 do
+				if self.detectors[i] == d then
 					table.remove(self.detectors, i)
 					break
 				end
@@ -270,7 +273,9 @@ local axis_mt = {
 			self.val, self.raw, self.max = val, raw, max
 			updated[self] = true
 		end
-	end
+	end,
+
+	--- LÖVE note: other callbacks that are defined in backend/love.lua and need to be called in the associated LÖVE callbacks.
 }
 axis_mt.__index = axis_mt
 
@@ -382,9 +387,9 @@ local pointer_mt = {
 	x = function(self)
 		if self.grabbing == self then
 			self:update()
-			return self.valX + (self.offsetX or self.width or input.drawWidth/2)
+			return self.valX + (self.offsetX or self.width or input.getDrawWidth()/2)
 		else
-			return self.offsetX or self.width or input.drawWidth/2
+			return self.offsetX or self.width or input.getDrawWidth()/2
 		end
 	end,
 	--- Returns the current Y value of the pointer.
@@ -392,9 +397,9 @@ local pointer_mt = {
 	y = function(self)
 		if self.grabbing == self then
 			self:update()
-			return self.valY + (self.offsetY or self.height or input.drawHeight/2)
+			return self.valY + (self.offsetY or self.height or input.getDrawHeight()/2)
 		else
-			return self.offsetY or self.height or input.drawHeight/2
+			return self.offsetY or self.height or input.getDrawHeight()/2
 		end
 	end,
 
@@ -418,9 +423,9 @@ local pointer_mt = {
 				local magnitude = sqrt(x*x + y*y)
 				cx, cy = cx / magnitude * width, cy / magnitude * height
 			end
-			return cx + (self.offsetX or width or input.drawWidth/2), cy + (self.offsetY or height or input.drawHeight/2)
+			return cx + (self.offsetX or width or input.getDrawWidth()/2), cy + (self.offsetY or height or input.getDrawHeight()/2)
 		else
-			return self.offsetX or width or input.drawWidth/2, self.offsetY or height or input.drawHeight/2
+			return self.offsetX or width or input.getDrawWidth()/2, self.offsetY or height or input.getDrawHeight()/2
 		end
 	end,
 
@@ -445,7 +450,7 @@ local pointer_mt = {
 		if not updated[self] then
 			local x, y = self.valX, self.valY
 			local xSpeed, ySpeed = self.xSpeed, self.ySpeed
-			local width, height = self.width or input.drawWidth/2, self.height or input.drawHeight/2
+			local width, height = self.width or input.getDrawWidth()/2, self.height or input.getDrawHeight()/2
 			local newX, newY = x, y
 			local maxMovX, maxMovY = 0, 0 -- the maxium axis movement in a direction (used to determine which axes have the priority) (absolute value)
 			for _, pointer in ipairs(self.detectors) do
@@ -642,16 +647,16 @@ input = {
 
 	--- Returns a list of the buttons currently in use, identified by their string button identifier.
 	-- This may also returns "axis threshold" buttons if an axis passes the threshold.
-	-- @treturn table<string> buttons identifiers list
-	-- @treturn[opt=0.5] number threshold the threshold to detect axes as button
+	-- @tparam[opt=0.5] number threshold the threshold to detect axes as button
+	-- @treturn string,... buttons identifiers list
 	-- @impl backend
-	buttonsInUse = function(threshold) end,
+	buttonUsed = function(threshold) end,
 
 	--- Returns a list of the axes currently in use, identified by their string axis identifier
-	-- @treturn table<string> axes identifiers list
-	-- @treturn[opt=0.5] number threshold the threshold to detect axes
+	-- @tparam[opt=0.5] number threshold the threshold to detect axes
+	-- @treturn string,... axes identifiers list
 	-- @impl backend
-	axesInUse = function(threshold) end,
+	axisUsed = function(threshold) end,
 
 	--- Returns a nice name for the button identifier.
 	-- Can be locale-depedant and stuff, it's only for display.
@@ -686,14 +691,14 @@ input = {
 		cancel = nil -- Button: used to cancel something. Example binds: Escape, B button.
 	},
 
-	--- Draw area dimensions.
+	--- Get draw area dimensions.
 	-- Used for pointers.
 	-- @impl backend
-	drawWidth = 1,
-	drawHeight = 1,
+	getDrawWidth = function() return 1 end,
+	getDrawHeight = function() return 1 end,
 
 	--- Update all the Inputs.
-	-- Should be called at every game update; called by ubiquitousse.update.
+	-- Should be called at every game update. If ubiquitousse.signal is available, will be bound to the "update" signal in signal.event.
 	-- The backend can hook into this function to to its input-related updates.
 	-- @tparam numder dt the delta-time
 	-- @impl ubiquitousse
@@ -701,6 +706,11 @@ input = {
 		dt = newDt
 		updated = {}
 	end
+
+	--- If you use LÖVE, note that in order to provide every feature (especially key detection), several callbacks functions will
+	-- need to be called on LÖVE events. See backend/love.lua.
+	-- If ubiquitousse.signal is available, these callbacks will be bound to signals in signal.event (with the same name as the LÖVE
+	-- callbacks, minux the "love.").
 }
 
 -- Create default inputs
@@ -708,4 +718,9 @@ input.default.pointer = input.pointer()
 input.default.confirm = input.button()
 input.default.cancel = input.button()
 
+-- Bind signals
+if signal then
+	signal.event:bind("update", input.update)
+end
+
 return input
diff --git a/scene/scene.lua b/scene/scene.lua
index 5db7095..de6525e 100644
--- a/scene/scene.lua
+++ b/scene/scene.lua
@@ -1,5 +1,8 @@
 --- ubiquitousse.scene
 -- Optional dependencies: ubiquitousse.timer (to provide each scene a timer registry)
+-- Optional dependencies: ubiquitousse.signal (to bind to update and draw signal in signal.event)
+local loaded, signal = pcall(require, (...):match("^(.-)scene").."signal")
+if not loaded then signal = nil end
 local loaded, timer = pcall(require, (...):match("^(.-)scene").."timer")
 if not loaded then timer = nil end
 
@@ -134,8 +137,16 @@ scene = setmetatable({
 		table.remove(scene.stack)
 	end,
 
+	--- Pop all scenes.
+	-- @impl ubiquitousse
+	popAll = function()
+		while scene.current do
+			scene.pop()
+		end
+	end,
+
 	--- Update the current scene.
-	-- Should be called at every game update; called by ubiquitousse.update.
+	-- Should be called at every game update. If ubiquitousse.signal is available, will be bound to the "update" signal in signal.event.
 	-- @tparam number dt the delta-time (milisecond)
 	-- @param ... arguments to pass to the scene's update function after dt
 	-- @impl ubiquitousse
@@ -147,7 +158,7 @@ scene = setmetatable({
 	end,
 
 	--- Draw the current scene.
-	-- Should be called every time the game is draw; called by ubiquitousse.draw.
+	-- Should be called every time the game is draw. If ubiquitousse.signal is available, will be bound to the "draw" signal in signal.event.
 	-- @param ... arguments to pass to the scene's draw function
 	-- @impl ubiquitousse
 	draw = function(...)
@@ -160,4 +171,10 @@ scene = setmetatable({
 	end
 })
 
+-- Bind signals
+if signal then
+	signal.event:bind("update", scene.update)
+	signal.event:bind("draw", scene.draw)
+end
+
 return scene
diff --git a/signal/backend/love.lua b/signal/backend/love.lua
new file mode 100644
index 0000000..b93570c
--- /dev/null
+++ b/signal/backend/love.lua
@@ -0,0 +1,43 @@
+local signal = require((...):match("^(.-%.)backend").."signal")
+
+function signal.registerEvents()
+	local callbacks = { -- everything except run, errorhandler, threaderror
+		"displayrotated", "draw", "load", "lowmemory", "quit", "update",
+		"directorydropped", "filedropped", "focus", "mousefocus", "resize", "visible",
+		"keypressed", "keyreleased", "textedited", "textinput",
+		"mousemoved", "mousepressed", "mousereleased", "wheelmoved",
+		"gamepadaxis", "gamepadpressed", "gamepadreleased",
+		"joystickadded", "joystickaxis", "joystickhat", "joystickpressed", "joystickreleased", "joystickremoved",
+		"touchmoved", "touchpressed", "touchreleased"
+	}
+	local event = signal.event
+	for _, callback in ipairs(callbacks) do
+		if callback == "update" then
+			if love[callback] then
+				local old = love[callback]
+				love[callback] = function(dt)
+					old(dt)
+					event:emit(callback, dt*1000)
+				end
+			else
+				love[callback] = function(dt)
+					event:emit(callback, dt*1000)
+				end
+			end
+		else
+			if love[callback] then
+				local old = love[callback]
+				love[callback] = function(...)
+					old(...)
+					event:emit(callback, ...)
+				end
+			else
+				love[callback] = function(...)
+					event:emit(callback, ...)
+				end
+			end
+		end
+	end
+end
+
+return signal
diff --git a/signal/init.lua b/signal/init.lua
new file mode 100644
index 0000000..827b528
--- /dev/null
+++ b/signal/init.lua
@@ -0,0 +1,14 @@
+local signal
+
+local p = ...
+if love then
+	signal = require(p..".backend.love")
+elseif package.loaded["ctr"] then
+	error("NYI")
+elseif package.loaded["libretro"] then
+	error("NYI")
+else
+	error("no backend for ubiquitousse.signal")
+end
+
+return signal
\ No newline at end of file
diff --git a/signal/signal.can b/signal/signal.can
new file mode 100644
index 0000000..004160f
--- /dev/null
+++ b/signal/signal.can
@@ -0,0 +1,116 @@
+--- ubiquitousse.signal
+
+let registry_mt = {
+	--- Map of signals to list of listeners.
+	-- @impl ubiquitousse
+	signals = {},
+
+	--- Bind one or several functions to a signal name.
+	-- @impl ubiquitousse
+	bind = :(name, fn, ...)
+		if not @signals[name] then
+			@signals[name] = {}
+		end
+		table.insert(@signals[name], fn)
+		if ... then
+			return @bind(name, ...)
+		end
+	end,
+
+	--- Unbind one or several functions to a signal name.
+	-- @impl ubiquitousse
+	unbind = :(name, fn, ...)
+		if not @signals[name] then
+			return
+		end
+		for i=#@signals[name], 1, -1 do
+			if @signals[name] == fn then
+				table.remove(@signals[name], i)
+			end
+		end
+		if ... then
+			return @unbind(name, ...)
+		end
+	end,
+
+	--- Remove every bound function to a signal name.
+	-- @impl ubiquitousse
+	unbindAll = :(name)
+		@signals[name] = nil
+	end,
+
+	--- Replace a bound function with another function.
+	-- @impl ubiquitousse
+	replace = :(name, sourceFn, destFn)
+		if not @signals[name] then
+			@signals[name] = {}
+		end
+		for i, fn in ipairs(@signals[name]) do
+			if fn == sourceFn then
+				@signals[name][i] = destFn
+				break
+			end
+		end
+	end,
+
+	--- Remove every bound function to every signal.
+	-- @impl ubiquitousse
+	clear = :()
+		@signals = {}
+	end,
+
+	--- Emit a signal, i.e. call every function bound to it, with the given arguments.
+	-- @impl ubiquitousse
+	emit = :(name, ...)
+		if @signals[name] then
+			for _, fn in ipairs(@signals[name]) do
+				fn(...)
+			end
+		end
+	end
+}
+registry_mt.__index = registry_mt
+
+let signal = {
+	--- Creates and return a new SignalRegistry.
+	-- A SignalRegistry is a separate ubiquitousse.signal instance: its signals will be independant from other registries.
+	-- @impl ubiquitousse
+	new = ()
+		return setmetatable({ signals = {} }, registry_mt)
+	end,
+	
+	--- Global SignalRegistry.
+	-- @impl ubiquitousse
+	signals = {},
+	bind = (...)
+		return registry_mt.bind(signal, ...)
+	end,
+	unbind = (...)
+		return registry_mt.unbind(signal, ...)
+	end,
+	clear = (...)
+		return registry_mt.clear(signal, ...)
+	end,
+	emit = (...)
+		return registry_mt.emit(signal, ...)
+	end,
+
+	--- SignalRegistry which will be used to bind signals that need to be called on game engine event.
+	-- For example, every ubiquitousse module with a "update" function will bind it to the "update" signal in the registry;
+	-- you can then call this signal on each game update to update every ubiquitousse module easily.
+	-- Provided signals:
+	-- * update, should be called on every game update
+	-- * draw, should be called on every game draw
+	-- * for LÖVE, there are callbacks for every LÖVE callback function that need to be called on their corresponding LÖVE callback
+	-- @impl mixed
+	event = nil,
+
+	--- Call this function to hook signal.event signals to the current backend.
+	-- For LÖVE, this means overriding every existing LÖVE callback. If a callback is already defined, the new one will call the old function along with the signal:emit.
+	-- @impl backend
+	registerEvents = () end
+}
+
+signal.event = signal.new()
+
+return signal
diff --git a/timer/timer.lua b/timer/timer.lua
index 3f2840b..a17ef44 100644
--- a/timer/timer.lua
+++ b/timer/timer.lua
@@ -1,5 +1,9 @@
 --- ubiquitousse.timer
 -- Depends on a backend.
+-- Optional dependencies: ubiquitousse.signal (to bind to update signal in signal.event)
+local loaded, signal = pcall(require, (...):match("^(.-)timer").."signal")
+if not loaded then signal = nil end
+
 local ease = require((...):match("^.-timer")..".easing")
 local timer
 
@@ -332,7 +336,7 @@ timer = {
 	-- @impl ubiquitousse
 	delayed = {},
 	lastTime = 0,
-	update = function(...)
+	update = function(...) -- If ubiquitousse.signal is available, will be bound to the "update" signal in signal.event.
 		return registry_mt.update(timer, ...)
 	end,
 	run = function(...)
@@ -346,4 +350,9 @@ timer = {
 	end
 }
 
+-- Bind signals
+if signal then
+	signal.event:bind("update", timer.update)
+end
+
 return timer