Step 3 : Scrolling background
Ok, let's show some graphics. Let's begin with a classic scrolling background. In practice, nothing is ever scrolled, what is happening is just that we draw a bitmap image at different vertical offsets many times each second, to give the illusion that it is moving.
Our scrolling background tile.
Download the file back2.png and save it to your Breakout\Common\res folder. If you instead would like a brighter background you can download back1.png instead. Add the file to your Visual Studio project as a PNG image and name it IDB_BACKGROUND.
Add the following code to myapplication.h:
class CMyApplication : public CGapiApplication { ... int m_nBackScrollIndex; CGapiSurface* m_pBackground; ... }
Add the following code to myapplication.cpp:
CMyApplication::CMyApplication(const GDAPPCONFIG& config) : CGapiApplication(config) { ... m_nBackScrollIndex = 0; m_pBackground = new CGapiSurface(GetGlobal()); ... } CMyApplication::~CMyApplication() { ... delete m_pBackground; ... } HRESULT CMyApplication::CreateVidMemSurfaces(CGapiSurface* pBackBuffer, HINSTANCE hInstance) { ... m_pBackground->CreateSurface(0, hInstance, IDB_BACKGROUND, _T("PNG")); ... } HRESULT CMyApplication::GameDrawBackgrund(CGapiSurface* pBackBuffer) { int nScreenWidth = pBackBuffer->GetWidth(); int nScreenHeight = pBackBuffer->GetHeight(); // Draw scrolling bitmap int nBackWidth = m_pBackground->GetWidth(); int nBackHeight = m_pBackground->GetHeight(); int nNumXBlits = pBackBuffer->GetWidth() / nBackWidth + 1; int nNumYBlits = pBackBuffer->GetHeight() / nBackHeight + 2; // One extra due to scrolling int nX, nY; for (nY=0; nY < nNumYBlits; nY++) { for (nX=0; nX < nNumXBlits; nX++) { pBackBuffer->BltFast(nX*nBackWidth, -nBackHeight+nY*nBackHeight+m_nBackScrollIndex, m_pBackground, NULL, 0, NULL); } } if (m_nBackScrollIndex++ == nBackWidth) { m_nBackScrollIndex = 0; } return S_OK; }
Yes, we have a scrolling bitmap on the display!
Now on to adding some nice border graphics!
