Get wrong size screen and sprite when add multi resolution (win32)

cocos2d-x C++
#1

I use project-creator to create project.
And then, i test multi resolution on win 32, i read this link :
http://www.cocos2d-x.org/wiki/Multi_resolution_support
In Appdelegate:

`CCDirector* pDirector = CCDirector::sharedDirector();
CCEGLView* pEGLView = CCEGLView::sharedOpenGLView();

pDirector->setOpenGLView(pEGLView);

// turn on display FPS
pDirector->setDisplayStats(true);


// Set the design resolution
pEGLView->setDesignResolutionSize(designResolutionSize.width, designResolutionSize.height, kResolutionNoBorder);

CCSize frameSize = pEGLView->getFrameSize();

// In this demo, we select resource according to the frame's height.
// If the resource size is different from design resolution size, you need to set contentScaleFactor.
// We use the ratio of resource's height to the height of design resolution,
// this can make sure that the resource's height could fit for the height of design resolution.

// if the frame's height is larger than the height of medium resource size, select large resource.
if (frameSize.height > mediumResource.size.height)
{ 
	searchPath.push_back(largeResource.directory);
	pDirector->setContentScaleFactor(largeResource.size.height/designResolutionSize.height);
}
// if the frame's height is larger than the height of small resource size, select medium resource.
else if (frameSize.height > smallResource.size.height)
{ 
	searchPath.push_back(mediumResource.directory);
	pDirector->setContentScaleFactor(mediumResource.size.height/designResolutionSize.height);
}
// if the frame's height is smaller than the height of medium resource size, select small resource.
else
{ 
	searchPath.push_back(smallResource.directory);
	pDirector->setContentScaleFactor(smallResource.size.height/designResolutionSize.height);
}

CCFileUtils::sharedFileUtils()->setSearchPaths(searchPath);`

but in helloworldscene, when i get size of screen like:

CCSize winSize = CCDirector::sharedDirector()->getWinSize();

or get size of sprite:
m_background = CCSprite::create("background.png"); this->addChild(m_background); CCLog("size: %f",m_background->boundingBox().size.width);
it give wrong size, and if i turn off multi resolution, it give right size. i dont’ understand why!!!