CMyView继承了CScrollView,采用双缓存显示位图。打开位图显示时不会闪烁,只有当拖动滚动条时,会闪烁,如何解决?部分代码如下,其中CMemDC是Keith Rule 02/11/02 更新的Memory DC类,代码在最后:void CMyView::OnDraw(CDC* pDC)
{
CLPCLR_TestDoc* pDoc = GetDocument();
ASSERT_VALID(pDoc); CMemDC memDC(pDC); SetDIBitsToDevice(
memDC.m_hDC, SPAN_CX, m_cyImgDisplay, // 在不为(0,0)的固定位置显示图像
pDoc->m_Image.cx,
pDoc->m_Image.cy,
0, 0, 0,
pDoc->m_Image.cy,
pDoc->m_Image.data,
(BITMAPINFO*) &(pDoc->m_Image.bi),
DIB_RGB_COLORS
);
}BOOL CMyView::OnEraseBkgnd(CDC* pDC)
{
// TODO: Add your message handler code here and/or call default
return TRUE;
}////////////////////////////////////////////////////////////////////////
class CMemDC : public CDC
{
private:
CBitmap m_bitmap; // Offscreen bitmap
CBitmap* m_oldBitmap; // bitmap originally found in CMemDC
CDC* m_pDC; // Saves CDC passed in constructor
CRect m_rect; // Rectangle of drawing area.
BOOL m_bMemDC; // TRUE if CDC really is a Memory DC.public:
CMemDC(CDC* pDC, const CRect* pRect = NULL)
: CDC()
, m_oldBitmap(NULL)
, m_pDC(pDC)
{
ASSERT(pDC != NULL);
// Some initialization
m_bMemDC = !pDC->IsPrinting();
// Get the rectangle to draw
if (pRect == NULL)
{
pDC->GetClipBox(&m_rect);
}
else
{
m_rect = *pRect;
}
if (m_bMemDC)
{
// Create a Memory DC
CreateCompatibleDC(pDC);
pDC->LPtoDP(&m_rect);
m_bitmap.CreateCompatibleBitmap(pDC, m_rect.Width(), m_rect.Height()); m_oldBitmap = SelectObject(&m_bitmap);
SetMapMode(pDC->GetMapMode());
SetWindowExt(pDC->GetWindowExt());
SetViewportExt(pDC->GetViewportExt());
pDC->DPtoLP(&m_rect);
SetWindowOrg(m_rect.left, m_rect.top);
}
else
{
// Make a copy of the relevent parts of the current
// DC for printing
m_bPrinting = pDC->m_bPrinting;
m_hDC = pDC->m_hDC;
m_hAttribDC = pDC->m_hAttribDC;
}
// Fill background
FillSolidRect(m_rect, pDC->GetBkColor());
}
~CMemDC()
{
if (m_bMemDC)
{
// Copy the offscreen bitmap onto the screen.
m_pDC->BitBlt(m_rect.left, m_rect.top,
m_rect.Width(), m_rect.Height(),
this, m_rect.left, m_rect.top, SRCCOPY);
//Swap back the original bitmap.
SelectObject(m_oldBitmap);
}
else
{
// All we need to do is replace the DC with an illegal
// value, this keeps us from accidentally deleting the
// handles associated with the CDC that was passed to
// the constructor.
m_hDC = m_hAttribDC = NULL;
}
}
// Allow usage as a pointer
CMemDC* operator->()
{
return this;
}
// Allow usage as a pointer
operator CMemDC*()
{
return this;
}
};
{
CLPCLR_TestDoc* pDoc = GetDocument();
ASSERT_VALID(pDoc); CMemDC memDC(pDC); SetDIBitsToDevice(
memDC.m_hDC, SPAN_CX, m_cyImgDisplay, // 在不为(0,0)的固定位置显示图像
pDoc->m_Image.cx,
pDoc->m_Image.cy,
0, 0, 0,
pDoc->m_Image.cy,
pDoc->m_Image.data,
(BITMAPINFO*) &(pDoc->m_Image.bi),
DIB_RGB_COLORS
);
}BOOL CMyView::OnEraseBkgnd(CDC* pDC)
{
// TODO: Add your message handler code here and/or call default
return TRUE;
}////////////////////////////////////////////////////////////////////////
class CMemDC : public CDC
{
private:
CBitmap m_bitmap; // Offscreen bitmap
CBitmap* m_oldBitmap; // bitmap originally found in CMemDC
CDC* m_pDC; // Saves CDC passed in constructor
CRect m_rect; // Rectangle of drawing area.
BOOL m_bMemDC; // TRUE if CDC really is a Memory DC.public:
CMemDC(CDC* pDC, const CRect* pRect = NULL)
: CDC()
, m_oldBitmap(NULL)
, m_pDC(pDC)
{
ASSERT(pDC != NULL);
// Some initialization
m_bMemDC = !pDC->IsPrinting();
// Get the rectangle to draw
if (pRect == NULL)
{
pDC->GetClipBox(&m_rect);
}
else
{
m_rect = *pRect;
}
if (m_bMemDC)
{
// Create a Memory DC
CreateCompatibleDC(pDC);
pDC->LPtoDP(&m_rect);
m_bitmap.CreateCompatibleBitmap(pDC, m_rect.Width(), m_rect.Height()); m_oldBitmap = SelectObject(&m_bitmap);
SetMapMode(pDC->GetMapMode());
SetWindowExt(pDC->GetWindowExt());
SetViewportExt(pDC->GetViewportExt());
pDC->DPtoLP(&m_rect);
SetWindowOrg(m_rect.left, m_rect.top);
}
else
{
// Make a copy of the relevent parts of the current
// DC for printing
m_bPrinting = pDC->m_bPrinting;
m_hDC = pDC->m_hDC;
m_hAttribDC = pDC->m_hAttribDC;
}
// Fill background
FillSolidRect(m_rect, pDC->GetBkColor());
}
~CMemDC()
{
if (m_bMemDC)
{
// Copy the offscreen bitmap onto the screen.
m_pDC->BitBlt(m_rect.left, m_rect.top,
m_rect.Width(), m_rect.Height(),
this, m_rect.left, m_rect.top, SRCCOPY);
//Swap back the original bitmap.
SelectObject(m_oldBitmap);
}
else
{
// All we need to do is replace the DC with an illegal
// value, this keeps us from accidentally deleting the
// handles associated with the CDC that was passed to
// the constructor.
m_hDC = m_hAttribDC = NULL;
}
}
// Allow usage as a pointer
CMemDC* operator->()
{
return this;
}
// Allow usage as a pointer
operator CMemDC*()
{
return this;
}
};
CFEDoc* pDoc = GetDocument();
ASSERT_VALID(pDoc);
CSize size = pDoc->m_ImageSize; // 要显示的图片的大小 int x=0, y=0;
CRect rt;
GetClientRect(&rt);
if (rt.Width() > size.cx) { //窗口宽度大于画布宽度
x = rt.Width() - size.cx;
x /= 2;
}
if (rt.Height() > size.cy) { //窗口高度大于画布高度
y = rt.Height() - size.cy;
y /= 2;
}
// 裁减区域...
pDC->ExcludeClipRect(0, 0, rt.Width(), y);
pDC->ExcludeClipRect(0, 0, x, rt.Height());
pDC->ExcludeClipRect(rt.Width()-x, 0, rt.Width(), rt.Height());
pDC->ExcludeClipRect(0, rt.Height()-y, rt.Width(), rt.Height()); // 设置原点和视口
pDC->SetViewportOrg(pDC->GetViewportOrg().x+x, pDC->GetViewportOrg().y+y);
pDC->SetViewportExt(size);
pDC->BitBlt(***); // ...将内存dc放到视图上
//... 其他代码另外OnSize中也要做类似转换:
CScrollView::OnSize(nType, cx, cy);
if ((HDC)m_DC == NULL) return;
CSize size = GetDocument()->m_ImageSize; // 图片大小
int x=0, y=0;
CRect rt;
GetClientRect(&rt);
if (rt.Width() > size.cx) { //窗口宽度大于画布宽度
x = rt.Width() - size.cx;
x /= 2;
}
if (rt.Height() > size.cy) { //窗口高度大于画布高度
y = rt.Height() - size.cy;
y /= 2;
} m_DC.SelectClipRgn(NULL, RGN_COPY);
if ((HRGN)(m_clipRgn) != NULL) {
m_clipRgn.DeleteObject();
}
CPoint pos = GetScrollPosition();
m_DC.SetViewportOrg(-pos.x+x, -pos.y+y);
m_clipRgn.CreateRectRgn(-pos.x+x, -pos.y+y, -pos.x+x+size.cx, -pos.y+y+size.cy);
m_DC.SelectClipRgn(&m_clipRgn, RGN_COPY);
[email protected]
or [email protected]