First demo commit.

lib/gamestate.lua

@@ -0,0 +1,93 @@
+--[[
+Copyright (c) 2010-2013 Matthias Richter
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+The above copyright notice and this permission notice shall be included in
+all copies or substantial portions of the Software.
+Except as contained in this notice, the name(s) of the above copyright holders
+shall not be used in advertising or otherwise to promote the sale, use or
+other dealings in this Software without prior written authorization.
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+THE SOFTWARE.
+]]--
+
+local function __NULL__() end
+
+ -- default gamestate produces error on every callback
+local state_init = setmetatable({leave = __NULL__},
+		{__index = function() error("Gamestate not initialized. Use Gamestate.switch()") end})
+local stack = {state_init}
+
+local GS = {}
+function GS.new(t) return t or {} end -- constructor - deprecated!
+
+function GS.switch(to, ...)
+	assert(to, "Missing argument: Gamestate to switch to")
+	assert(to ~= GS, "Can't call switch with colon operator")
+	local pre = stack[#stack]
+	;(pre.leave or __NULL__)(pre)
+	;(to.load or __NULL__)(to)
+	to.load = nil
+	stack[#stack] = to
+	return (to.enter or __NULL__)(to, pre, ...)
+end
+
+function GS.push(to, ...)
+	assert(to, "Missing argument: Gamestate to switch to")
+	assert(to ~= GS, "Can't call push with colon operator")
+	local pre = stack[#stack]
+	;(to.load or __NULL__)(to)
+	to.load = nil
+	stack[#stack+1] = to
+	return (to.enter or __NULL__)(to, pre, ...)
+end
+
+function GS.pop(...)
+	assert(#stack > 1, "No more states to pop!")
+	local pre, to = stack[#stack], stack[#stack-1] 
+	stack[#stack] = nil
+	;(pre.leave or __NULL__)(pre)
+	return (to.resume or __NULL__)(to, pre, ...)
+end
+
+function GS.current()
+	return stack[#stack]
+end
+
+local all_callbacks = {
+	'draw', 'errhand', 'focus', 'keypressed', 'keyreleased', 'mousefocus',
+	'mousemoved', 'mousepressed', 'mousereleased', 'quit', 'resize',
+	'textinput', 'threaderror', 'update', 'visible', 'gamepadaxis',
+	'gamepadpressed', 'gamepadreleased', 'joystickadded', 'joystickaxis',
+	'joystickhat', 'joystickpressed', 'joystickreleased', 'joystickremoved'
+}
+
+function GS.registerEvents(callbacks)
+	local registry = {}
+	callbacks = callbacks or all_callbacks
+	for _, f in ipairs(callbacks) do
+		registry[f] = love[f] or __NULL__
+		love[f] = function(...)
+			registry[f](...)
+			return GS[f](...)
+		end
+	end
+end
+
+-- forward any undefined functions
+setmetatable(GS, {__index = function(_, func)
+	return function(...)
+		return (stack[#stack][func] or __NULL__)(stack[#stack], ...)
+	end
+end})
+
+return GS