难题，在一背景图片上放一个CSliderCtrl控件，如何让此控件透明？

djhdu 2003-02-12 01:41:48

也就是如何实现一个透明的CSliderCtrl控件！

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Gargamel 2003-02-13

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留个邮箱，发给你一个demo

kingzai 2003-02-13

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in your CSliderCtrl derived class, in your OnPaint message handler,
first let the control draw itself into a memory dc, then draw it
transparently on the screen using COLOR_BTNFACE as tranparent color.

See http://www.codeguru.com/treeview/background_image.shtml for an
example on how to implement it.

djhdu 2003-02-13

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怎么没有人帮助我啊？

chenzhou35 2003-02-13

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// MySliderControl.cpp : implementation file
//
//
// Copyright (C) 2001 by Nic Wilsonk
// All rights reserved
//
// This is free software.
// This code may be used in compiled form in any way you desire. This
// file may be redistributed unmodified by any means PROVIDING it is
// not sold for profit without the authors written consent, and
// providing that this notice and the authors name and all copyright
// notices remains intact. If the source code in this file is used in
// any commercial application then a statement along the lines of
// "Portions Copyright ?2001 Nic Wilson" must be included in
// the startup banner, "About" box and printed documentation. An email
// letting me know that you are using it would be nice.
//
// No warrantee of any kind, expressed or implied, is included with this
// software; use at your own risk, responsibility for damages (if any) to
// anyone resulting from the use of this software rests entirely with the
// user.
//
// Version: 1.0
// Release: 1 (www.codeguru.com)
// -----------------------------------------------------------------------
/////////////////////////////////////////////////////////////////////////////
#include "stdafx.h"
#include "MySliderControl.h"
#include "windows.h"

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

/////////////////////////////////////////////////////////////////////////////
// CMySliderControl

CMySliderControl::CMySliderControl()
{
m_dcBk.m_hDC = NULL;
}

CMySliderControl::~CMySliderControl()
{
DeleteObject(m_dcBk.SelectObject(&m_bmpBkOld));
DeleteDC(m_dcBk);
}

BEGIN_MESSAGE_MAP(CMySliderControl, CSliderCtrl)
//{{AFX_MSG_MAP(CMySliderControl)
ON_NOTIFY_REFLECT(NM_CUSTOMDRAW, OnCustomDraw)
ON_WM_ERASEBKGND()
//}}AFX_MSG_MAP
END_MESSAGE_MAP()

/////////////////////////////////////////////////////////////////////////////
// CMySliderControl message handlers
//-------------------------------------------------------------------
//
void CMySliderControl::OnCustomDraw(NMHDR* pNMHDR, LRESULT* pResult)
//
// Description : Sent by the slider control to notify the parent window
// about drawing operations. This notification is sent in
// the form of a WM_NOTIFY message.
// Parameters : pNMHDR - a pointer to a NM_CUSTOMDRAW structure.
// pResult - value depends on the current drawing state.
{
LPNMCUSTOMDRAW lpcd = (LPNMCUSTOMDRAW)pNMHDR;
CDC *pDC = CDC::FromHandle(lpcd->hdc);
switch(lpcd->dwDrawStage)
{
case CDDS_PREPAINT:
*pResult = CDRF_NOTIFYITEMDRAW ;
TRACE("CDDS_PREPAINT\n");
break;
//return;
case CDDS_ITEMPREPAINT:
TRACE("CDDS_ITEMPREPAINT\n");
if (lpcd->dwItemSpec == TBCD_THUMB)
{
*pResult = CDRF_DODEFAULT;
TRACE("TBCD_THUMB\n");
break;
}
if(lpcd->dwItemSpec == TBCD_TICS )
{
TRACE("TBCD_TICS\n");
break;
}
if (lpcd->dwItemSpec == TBCD_CHANNEL)
{
TRACE("TBCD_CHANNEL\n");
CClientDC clientDC(GetParent());
CRect crect;
CRect wrect;
GetClientRect(crect);
GetWindowRect(wrect);
GetParent()->ScreenToClient(wrect);
if (m_dcBk.m_hDC == NULL)
{
m_dcBk.CreateCompatibleDC(&clientDC);
m_bmpBk.CreateCompatibleBitmap(&clientDC, crect.Width(), crect.Height());
m_bmpBkOld = m_dcBk.SelectObject(&m_bmpBk);
m_dcBk.BitBlt(0, 0, crect.Width(), crect.Height(), &clientDC, wrect.left, wrect.top, SRCCOPY);
}
//This bit does the tics marks transparently.
//create a memory dc to hold a copy of the oldbitmap data that includes the tics,
//because when we add the background in we will lose the tic marks
CDC SaveCDC;
CBitmap SaveCBmp, maskBitmap;
//set the colours for the monochrome mask bitmap
COLORREF crOldBack = pDC->SetBkColor(RGB(0,0,0));
COLORREF crOldText = pDC->SetTextColor(RGB(255,255,255));
CDC maskDC;
int iWidth = crect.Width();
int iHeight = crect.Height();
SaveCDC.CreateCompatibleDC(pDC);
SaveCBmp.CreateCompatibleBitmap(&SaveCDC, iWidth, iHeight);
CBitmap* SaveCBmpOld = (CBitmap *)SaveCDC.SelectObject(SaveCBmp);
//fill in the memory dc for the mask
maskDC.CreateCompatibleDC(&SaveCDC);
//create a monochrome bitmap
maskBitmap.CreateBitmap(iWidth, iHeight, 1, 1, NULL);
//select the mask bitmap into the dc
CBitmap* OldmaskBitmap = maskDC.SelectObject(&maskBitmap);
//copy the oldbitmap data into the bitmap, this includes the tics.
SaveCDC.BitBlt(0, 0, iWidth, iHeight, pDC, crect.left, crect.top, SRCCOPY);
//now copy the background into the slider
BitBlt(lpcd->hdc, 0, 0, iWidth, iHeight, m_dcBk.m_hDC, 0, 0, SRCCOPY);
// Blit the mask based on background colour
maskDC.BitBlt(0, 0, iWidth, iHeight, &SaveCDC, 0, 0, SRCCOPY);
// Blit the image using the mask
pDC->BitBlt(0, 0, iWidth, iHeight, &SaveCDC, 0, 0, SRCINVERT);
pDC->BitBlt(0, 0, iWidth, iHeight, &maskDC, 0, 0, SRCAND);
pDC->BitBlt(0, 0, iWidth, iHeight, &SaveCDC, 0, 0, SRCINVERT);
//restore and clean up
pDC->SetBkColor(crOldBack);
pDC->SetTextColor(crOldText);
DeleteObject(SelectObject(SaveCDC, SaveCBmpOld));
DeleteDC(SaveCDC);
DeleteObject(maskDC.SelectObject(OldmaskBitmap));
DeleteDC(maskDC);
*pResult = 0;
break;
}
}
}

BOOL CMySliderControl::OnEraseBkgnd(CDC* pDC)
{
return FALSE;
}

djhdu 2003-02-13