cachedscrollview.cpp

《Visual C／C++图形图像与游戏编程典型实例解析》配套源代码

// CachedScrollView.cpp : implementation file
//

#include "stdafx.h"
#include "CCachedScrollViewP.h"
#include "CachedScrollView.h"

#ifdef _DEBUG
#define new DEBUG_NEW
#undef THIS_FILE
static char THIS_FILE[] = __FILE__;
#endif

/////////////////////////////////////////////////////////////////////////////
// CCachedScrollView

IMPLEMENT_DYNCREATE(CCachedScrollView, CScrollView)

CCachedScrollView::CCachedScrollView()
{	CacheValid=FALSE;
	CacheRect=new CRect;

	CacheRect.SetRectEmpty();
}

CCachedScrollView::~CCachedScrollView()
{
	
}


BEGIN_MESSAGE_MAP(CCachedScrollView, CScrollView)
	//{{AFX_MSG_MAP(CCachedScrollView)
	ON_WM_PAINT()
	//}}AFX_MSG_MAP
END_MESSAGE_MAP()

/////////////////////////////////////////////////////////////////////////////
// CCachedScrollView drawing

void CCachedScrollView::OnInitialUpdate()
{
	CScrollView::OnInitialUpdate();

	CSize sizeTotal;
	// TODO: calculate the total size of this view
	sizeTotal.cx = sizeTotal.cy = 100;
	SetScrollSizes(MM_TEXT, sizeTotal);
}

void CCachedScrollView::OnDraw(CDC* pDC)
{
	CDocument* pDoc = GetDocument();
	// TODO: add draw code here
}

/////////////////////////////////////////////////////////////////////////////
// CCachedScrollView diagnostics

#ifdef _DEBUG
void CCachedScrollView::AssertValid() const
{
	CScrollView::AssertValid();
}

void CCachedScrollView::Dump(CDumpContext& dc) const
{
	CScrollView::Dump(dc);
}
#endif //_DEBUG

/////////////////////////////////////////////////////////////////////////////
// CCachedScrollView message handlers

void CCachedScrollView::OnPaint() 
{
	
	CPaintDC dc(this); // device context for painting
	OnPrepareDC(&dc);
	
	//无缓冲
	if (CacheRect.IsRectNull()) 
	{
		OnDraw(&dc);
		return;
	}
	
	//创建缓冲位图
	if (CacheBitmap.m_hObject==NULL) 
		CacheBitmap.CreateCompatibleBitmap(&dc,CacheRect.Width(),CacheRect.Height());
	
	CRect ClientRect;
	GetClientRect(ClientRect);
	
	CPoint org=dc.GetViewportOrg();
	ClientRect.OffsetRect(-org.x,-org.y);
	
	if (!CacheRect.PtInRect(ClientRect.TopLeft()) ||
		!CacheRect.PtInRect(ClientRect.BottomRight()))
	{
		CacheRect.OffsetRect(
			ClientRect.CenterPoint()-CacheRect.CenterPoint());
		CacheValid=FALSE;
	}
	
	CDC mdc;
	mdc.CreateCompatibleDC(&dc);
	mdc.SelectObject(&CacheBitmap);
	
	if (!CacheValid) {
		mdc.SelectStockObject(WHITE_BRUSH);
		mdc.SelectStockObject(NULL_PEN);
		mdc.Rectangle(0,0,CacheRect.Width(),CacheRect.Height());
		mdc.SelectStockObject(BLACK_PEN);
		mdc.SetViewportOrg(-CacheRect.left,-CacheRect.top);
		OnDraw(&mdc);
		mdc.SetViewportOrg(0,0);
		CacheValid=TRUE;
	}
	
	dc.SelectClipRgn(NULL);
	dc.BitBlt(CacheRect.left,CacheRect.top,
		CacheRect.Width(),CacheRect.Height(),&mdc,0,0,SRCCOPY);
	
	
}