WTL界面重画问题

sghcpt 2013-04-09 10:24:50

大家好，我的问题如下的。我需要实现一个截图的程序，当我点击鼠标开始截图时，可以成功画出截图的边框来，但当我需要拖拉右边框时，需要实现向右拖拉来增大截图的范围，就像qq截图可以拖拉右边框一样的功能。但是我面的代码，在拖拉右边框时，背景好像没有重新画出来，但我调试的时候，代码是有进入OnEraseBkgnd函数的，坐标也正确，请问那可能是什么问题引起的了？在此先谢谢帮忙的人。代码如下：

LRESULT CCatchScreenDlg::OnEraseBkgnd(UINT uMsg, WPARAM wParam, LPARAM lParam, BOOL& bHandled)

{

	CPaintDC dc(m_hWnd);



	CGuiRect rect;

	::GetClientRect(m_hWnd, &rect);

	HDC dcCompatible = ::CreateCompatibleDC(dc);

	HBITMAP hBmp = ::CreateCompatibleBitmap(dc, rect.GetWidth(), rect.GetHeight());

	HGDIOBJ tmp = ::SelectObject(dcCompatible, hBmp);

	if (m_pImgScreen)	//CxImage类的指针对象，保存了整个界面的图片

		m_pImgScreen->Draw(dcCompatible, rect.left, rect.top, rect.GetWidth(), rect.GetHeight(), NULL, TRUE);



	CMemoryDC memDC(dc, rect);   //WTL提供的双缓存，析构时自动绘制

	BLENDFUNCTION bf;

	bf.AlphaFormat = 0;

	bf.BlendFlags = 0;

	bf.BlendOp = AC_SRC_OVER;

	bf.SourceConstantAlpha = 100;

	memDC.AlphaBlend(0, 0, rect.GetWidth(), rect.GetHeight(), dcCompatible, 0, 0, rect.GetWidth(), rect.GetHeight(), bf);

	if (m_catchPicStatus == CATCHPICING)	//开始截图，就是刚开始点击鼠标拖拉时截图

	{

		RECT rc_catch;

		rc_catch.left = m_ptStart.x;

		rc_catch.top = m_ptStart.y;

		rc_catch.right = m_ptEnd.x;

		rc_catch.bottom = m_ptEnd.y;

		memDC.BitBlt(rc_catch.left, rc_catch.top,rc_catch.right-rc_catch.left,rc_catch.bottom-rc_catch.top,dcCompatible,rc_catch.left,rc_catch.top,SRCCOPY);

	}

	

	if (CATCHPICFINISH == m_catchPicStatus && m_bTrackPic) //结束截图，而且点击截图右边框时实现拖拉。

	{

		RECT rc_catch;

		rc_catch.left = m_ptStart.x;

		rc_catch.top = m_ptStart.y;

		rc_catch.right = m_ptEnd.x;

		rc_catch.bottom = m_ptEnd.y;

		TCHAR tszPos[100] = {0};

		wsprintf(tszPos, _T("left=%d,top=%d,right=%d,bottom=%d\n"), rc_catch.left, rc_catch.top, rc_catch.right, rc_catch.bottom);

		OutputDebugString(tszPos);



		memDC.BitBlt(rc_catch.left, rc_catch.top,rc_catch.right-rc_catch.left,rc_catch.bottom-rc_catch.top,dcCompatible,rc_catch.left,rc_catch.top,SRCCOPY);

	

	}

	::SelectObject(dcCompatible, tmp);

	::DeleteObject(hBmp);

	::DeleteDC(dcCompatible);

	return S_FALSE;

}

LRESULT CCatchScreenDlg::OnPaint(UINT uMsg, WPARAM wParam, LPARAM lParam, BOOL& bHandled)

{

	PAINTSTRUCT ps;

	HDC hdc = ::BeginPaint(m_hWnd, &ps);

	if (m_catchPicStatus == CATCHPICING || CATCHPICFINISH == m_catchPicStatus)

	{

		m_rectTracker.Draw(hdc);	//这个是画边框线

	}

	::EndPaint(m_hWnd, &ps);

	return 0;

}