读coco2d-x里的hellolua

里面自带的C++代码很简单。

但是里面有一句：

    std::string path = CCFileUtils::sharedFileUtils()->fullPathForFilename("hello.lua");
    pEngine->addSearchPath(path.substr(0, path.find_last_of("/")).c_str());
    pEngine->executeScriptFile(path.c_str());

就是从文件读lua文件bing执行。

好嘛，我们看下这个hello.lua代码是怎么样的：

（PS：我注释了一处非常滑稽的代码）

-- for CCLuaEngine traceback
function __G__TRACKBACK__(msg)
    print("----------------------------------------")
    print("LUA ERROR: " .. tostring(msg) .. "\n")
    print(debug.traceback())
    print("----------------------------------------")
end

function myadd(x, y)
    return x + y
end

local function main()
    -- avoid memory leak
    collectgarbage("setpause", 100)
    collectgarbage("setstepmul", 5000)

    local cclog = function(...)
        print(string.format(...))
    end

    --require "hello2"
    --cclog("result is " .. myadd(3, 5))

    ---------------

    local visibleSize = CCDirector:sharedDirector():getVisibleSize()
    local origin = CCDirector:sharedDirector():getVisibleOrigin()

    -- add the moving dog
    local function creatDog()
        local frameWidth = 105
        local frameHeight = 95

        -- create dog animate
        local textureDog = CCTextureCache:sharedTextureCache():addImage("dog.png")
        local rect = CCRectMake(0, 0, frameWidth, frameHeight)
        local frame0 = CCSpriteFrame:createWithTexture(textureDog, rect)
        rect = CCRectMake(frameWidth, 0, frameWidth, frameHeight)
        local frame1 = CCSpriteFrame:createWithTexture(textureDog, rect)

        local spriteDog = CCSprite:createWithSpriteFrame(frame0)
        spriteDog.isPaused = false
        spriteDog:setPosition(origin.x, origin.y + visibleSize.height / 4 * 3)

        local animFrames = CCArray:create()

        animFrames:addObject(frame0)
        animFrames:addObject(frame1)

        local animation = CCAnimation:createWithSpriteFrames(animFrames, 0.5)
        local animate = CCAnimate:create(animation);
        spriteDog:runAction(CCRepeatForever:create(animate))

        -- moving dog at every frame
        local function tick()
            if spriteDog.isPaused then return end
            local x, y = spriteDog:getPosition()
            if x > origin.x + visibleSize.width then
                x = origin.x
            else
                x = x + 1
            end

            spriteDog:setPositionX(x)
        end

        CCDirector:sharedDirector():getScheduler():scheduleScriptFunc(tick, 0, false)

        return spriteDog
    end

    -- create farm
    local function createLayerFarm()
        local layerFarm = CCLayer:create()

        -- add in farm background
        local bg = CCSprite:create("farm.jpg")
        bg:setPosition(origin.x + visibleSize.width / 2 + 80, origin.y + visibleSize.height / 2)
        layerFarm:addChild(bg)

        -- add land sprite
        for i = 0, 3 do
            for j = 0, 1 do
                local spriteLand = CCSprite:create("land.png")
                spriteLand:setPosition(200 + j * 180 - i % 2 * 90, 10 + i * 95 / 2)
                layerFarm:addChild(spriteLand)
            end
        end

        -- add crop
        local frameCrop = CCSpriteFrame:create("crop.png", CCRectMake(0, 0, 105, 95))
        for i = 0, 3 do
            for j = 0, 1 do
                local spriteCrop = CCSprite:createWithSpriteFrame(frameCrop);
                spriteCrop:setPosition(10 + 200 + j * 180 - i % 2 * 90, 30 + 10 + i * 95 / 2)
                layerFarm:addChild(spriteCrop)
            end
        end

        -- add moving dog
        local spriteDog = creatDog()
        layerFarm:addChild(spriteDog)

        -- handing touch events
        local touchBeginPoint = nil

        local function onTouchBegan(x, y)
            cclog("onTouchBegan: %0.2f, %0.2f", x, y)
            touchBeginPoint = {x = x, y = y}
            spriteDog.isPaused = true
            -- CCTOUCHBEGAN event must return true
            return true
        end

        local function onTouchMoved(x, y)
            cclog("onTouchMoved: %0.2f, %0.2f", x, y)
            if touchBeginPoint then
                local cx, cy = layerFarm:getPosition()
                layerFarm:setPosition(cx + x - touchBeginPoint.x,
                                      cy + y - touchBeginPoint.y)
                touchBeginPoint = {x = x, y = y}
            end
        end

        local function onTouchEnded(x, y)
            cclog("onTouchEnded: %0.2f, %0.2f", x, y)
            touchBeginPoint = nil
            spriteDog.isPaused = false
        end

        local function onTouch(eventType, x, y)
            if eventType == "began" then   
                return onTouchBegan(x, y)
            elseif eventType == "moved" then
                return onTouchMoved(x, y)
            else
                return onTouchEnded(x, y)
            end
        end

        layerFarm:registerScriptTouchHandler(onTouch)
        layerFarm:setTouchEnabled(true)

        return layerFarm
    end


    -- create menu
    local function createLayerMenu()
        local layerMenu = CCLayer:create()

        local menuPopup, menuTools, effectID

        local function menuCallbackClosePopup()
            -- stop test sound effect
            SimpleAudioEngine:sharedEngine():stopEffect(effectID)
            menuPopup:setVisible(false)
        end

        local function menuCallbackOpenPopup()
            -- loop test sound effect
            local effectPath = CCFileUtils:sharedFileUtils():fullPathForFilename("effect1.wav")
            effectID = SimpleAudioEngine:sharedEngine():playEffect(effectPath)
            menuPopup:setVisible(true)
        end

        -- add a popup menu
        local menuPopupItem = CCMenuItemImage:create("menu2.png", "menu2.png")
        menuPopupItem:setPosition(0, 0)
        menuPopupItem:registerScriptTapHandler(menuCallbackClosePopup)
        menuPopup = CCMenu:createWithItem(menuPopupItem)
        menuPopup:setPosition(origin.x + visibleSize.width / 2, origin.y + visibleSize.height / 2)
        menuPopup:setVisible(false)
        layerMenu:addChild(menuPopup)

        -- add the left-bottom "tools" menu to invoke menuPopup
        local menuToolsItem = CCMenuItemImage:create("menu1.png", "menu1.png")
        menuToolsItem:setPosition(0, 0)
        menuToolsItem:registerScriptTapHandler(menuCallbackOpenPopup)
        menuTools = CCMenu:createWithItem(menuToolsItem)
        local itemWidth = menuToolsItem:getContentSize().width
        local itemHeight = menuToolsItem:getContentSize().height
        menuTools:setPosition(origin.x + itemWidth/2, origin.y + itemHeight/2)
        layerMenu:addChild(menuTools)

        return layerMenu
    end

    -- play background music, preload effect

    -- uncomment below for the BlackBerry version
    -- local bgMusicPath = CCFileUtils:sharedFileUtils():fullPathForFilename("background.ogg")
    local bgMusicPath = CCFileUtils:sharedFileUtils():fullPathForFilename("background.mp3")
    SimpleAudioEngine:sharedEngine():playBackgroundMusic(bgMusicPath, true)
    local effectPath = CCFileUtils:sharedFileUtils():fullPathForFilename("effect1.wav")
    SimpleAudioEngine:sharedEngine():preloadEffect(effectPath)

    -- run
    local sceneGame = CCScene:create()
    sceneGame:addChild(createLayerFarm())
    sceneGame:addChild(createLayerMenu())
    CCDirector:sharedDirector():runWithScene(sceneGame)
end

xpcall(main, __G__TRACKBACK__)

那么我看看最上面提到的c++代码是如何调用lua的：

pEngine->executeScriptFile(path.c_str());

然后调用m_stack->executeScriptFile(filename);

这个m_strack是神马玩意呢？ 

其实在生成strack做了一些初始化工作：

    m_state = lua_open();
    luaL_openlibs(m_state);
    tolua_Cocos2d_open(m_state);
    toluafix_open(m_state);

啊啊，里面还用到了tolua库，就是把C++代码转成lua。关于tolua可以参考 http://www.codenix.com/~tolua/tolua++.html

tolua is a tool that greatly simplifies the integration of C/C++ code with Lua. Based on a cleaned header file (or extracts from real header files), toluaautomatically generates the binding code to access C/C++ features from Lua. Using Lua API and tag method facilities, tolua maps C/C++ constants, external variables, functions, classes, and methods to Lua.

关于cocod-2x里面的关于tolua可以直接看源码，有注释。

主要就是tolua_Cocos2d_open里完成了一些重要工作：

举个例子，上面的lua调用到CCTextureCache:sharedTextureCache():addImage("dog.png")，然后这里面就写得有：

比如将一个类加到luastate就可以这样：

  tolua_beginmodule(tolua_S,"CCTextureCache");
   tolua_function(tolua_S,"addImage",tolua_Cocos2d_CCTextureCache_addImage00);

   tolua_function(tolua_S,"sharedTextureCache",tolua_Cocos2d_CCTextureCache_sharedTextureCache00);
  tolua_endmodule(tolua_S);

这样就知道，为毛这个hello.lua可以这么轻松地调用coco2d-x里的API了。