memdc.h

工控软件图形界面-控件实现（温度计控件） 可用于工业控制系统开发使用的控件

class CMemDC : public CDC
{
public:
	CMemDC(CDC* pDC, LPRECT pRect = NULL, BOOL fCopyOld = FALSE, BOOL fUsePalette = FALSE) : CDC()
	{
		ASSERT(pDC != NULL);

		m_pDC = pDC;
		m_pOldBitmap = NULL;
		m_bMemDC = !pDC->IsPrinting();
		m_fUsePalette = fUsePalette;

		if (m_bMemDC) 
		{
			if(pRect)
				m_rect = *pRect;
			else
				pDC->GetClipBox(&m_rect);
			CreateCompatibleDC(pDC);
			m_bitmap.CreateCompatibleBitmap(pDC, m_rect.Width(), m_rect.Height());
			m_pOldBitmap = SelectObject(&m_bitmap);
			SetWindowOrg(m_rect.left, m_rect.top);
			if(fCopyOld)
				BitBlt(m_rect.left, m_rect.top, m_rect.Width(), m_rect.Height(),
				       m_pDC, m_rect.left, m_rect.top, SRCCOPY);
		}
		else  
		{
			m_bPrinting = pDC->m_bPrinting;
			m_hDC = pDC->m_hDC;
			m_hAttribDC = pDC->m_hAttribDC;
		}
	}
	
	~CMemDC()
	{
		if (m_bMemDC) 
		{	 
			CPalette pal, *pOldPal=NULL;
			if(m_fUsePalette && CreatePalette(pal))
			{
				pOldPal = m_pDC->SelectPalette(&pal, FALSE);
				m_pDC->RealizePalette();
			}
			m_pDC->BitBlt(m_rect.left, m_rect.top, m_rect.Width(), m_rect.Height(),
			              this, m_rect.left, m_rect.top, SRCCOPY);

			if(pOldPal)
				m_pDC->SelectPalette(pOldPal, TRUE);
			SelectObject(m_pOldBitmap);
		} 
		else 
		{
			m_hDC = m_hAttribDC = NULL;
		}
	}

	BOOL CreatePalette(CPalette& pal, CDC* pDC = NULL)
	{
		if(!pDC) pDC = this;
		if(!(pDC->GetDeviceCaps(RASTERCAPS) & RC_PALETTE))
			return FALSE;

		const int nColors = 236;
		RGBQUAD rgb[nColors];
		::GetDIBColorTable(pDC->m_hDC, 0, nColors, rgb);

		LPLOGPALETTE lpPal = (LPLOGPALETTE) new BYTE[sizeof(LOGPALETTE) + (nColors*sizeof(PALETTEENTRY))];
		lpPal->palVersion = 0x300;       
		lpPal->palNumEntries = nColors;

		for (int i = 0; i < nColors; i++)       
		{
			lpPal->palPalEntry[i].peRed = rgb[i].rgbRed;
			lpPal->palPalEntry[i].peGreen = rgb[i].rgbGreen;
			lpPal->palPalEntry[i].peBlue = rgb[i].rgbBlue;
			lpPal->palPalEntry[i].peFlags = 0;
		}
		VERIFY(pal.CreatePalette(lpPal));
  
		delete lpPal;
		return TRUE;
	}

	CMemDC* operator->() {return this;}
		
	operator CMemDC*() {return this;}

private:
	CBitmap  m_bitmap;      
	CBitmap* m_pOldBitmap;  
	CDC*     m_pDC;         
	CRect    m_rect;        
	BOOL     m_bMemDC;      
	BOOL     m_fUsePalette;
};