Skins in a Dialog-Based Application

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Environment: VC6

Introduction

This is a very simple example to implement a skin in a dialog-based application. The code is actually written by a friend of mine (sun@codefinger.de), so thanks go to him. I am just showing you how simple it is to use. Also, thanks to Davide Calabro, who gave me permission to use his CButtonST class.

Example

In my example, I use a simple, dialog-based app called "Skin." Import a bitmap you like for your dialog. In our case it's labeled IDB_MAIN. Create the following variables and functions in your dialog's header file.

CSkinDlg : public CDialog
{
  public: CSkinDlg();
  HBITMAP m_hBmp;
  HRGN m_hWndRgn;
  HRGN DIBToRgn(HBITMAP hBmp,COLORREF BkColor,BOOL Direct);
  // Handle the Skin . . .
}

In the Constructor, do the following:

CSkinDlg::CSkintDlg(CWnd* pParent /*=NULL*/) :
    CDialog(CSkinDlg::IDD, pParent)
{
  //{{AFX_DATA_INIT(CSkinDlg)
  //}}AFX_DATA_INIT
  m_hBmp=(HBITMAP)LoadImage(AfxGetApp()->m_hInstance,
    MAKEINTRESOURCE(IDB_MAIN), 
    IMAGE_BITMAP,0,0,LR_CREATEDIBSECTION); 
  m_hWndRgn=DIBToRgn(m_hBmp,0x00ff00,FALSE); 
}

Insert the function called HRGN DIBToRgn(HBITMAP hBmp, COLORREF BkColor, BOOL Direct) into your Dialog class and paste the following code into it.

HRGN CSkinDlg ::DIBToRgn(HBITMAP hBmp, COLORREF BkColor,
                         BOOL Direct)
{
  // use to return the handle of the HGRN
    HRGN hRgn = NULL;
    #define MAX_ALLOC_RECTS  100
    //the difference of the color
    COLORREF  Tolerance=0x00101010;
    if (hBmp)
    {
      //create the dib to save the dc
      HDC hMemDC = CreateCompatibleDC(NULL);
      if (hMemDC)
      {
        BITMAP bm;
        //get the info of the bitmap
        GetObject(hBmp, sizeof(bm), &bm);

        BITMAPINFOHEADER BmpInfoh = {
          // the struct of the bitmap
        sizeof(BITMAPINFOHEADER),   // biSize
          bm.bmWidth,               // biWidth;
          bm.bmHeight,              // biHeight;
          1,                        // biPlanes;
          32,                       // biBitCount
          BI_RGB,                   // biCompression;
          0,                        // biSizeImage;
          0,                        // biXPelsPerMeter;
          0,                        // biYPelsPerMeter;
          0,                        // biClrUsed;
          0                         // biClrImportant;
          };
          //design a void point to point to the bitmap
          LPVOID pBit32; 
          //creat a DIB
          HBITMAP hDib32 = CreateDIBSection(hMemDC, 
              (BITMAPINFO *)&BmpInfoh, 
              DIB_RGB_COLORS, &pBit32, NULL, 0);
            if (hDic32)
            {
              //copy dib to DC
              HBITMAP hOldib32 = (IBITMAP)SelectObject(hMemDC,
                                                       hDib32);
              // create a DC to save orginal bitmap
              HDC hDC = CreateCompatibleDC(hMemDC);
              if (hDC)
              {
                BITMAP bm32;
                // get the new 34-bit Dib size
                GetObject(hDib32, sizeof(bm32), &bm32);
                //make sure the 32Dib's every line pilex's is 4's
                //times
                while (bm32.bmWidthBytes % 4) bm32.bmWidthBytes++;
                //copy the orginal dib to DC
                HBITMAP holdBmp = (HBITMAP)SelectObject(hDC, hBmp);
                //copy dib to memory DC
                BitBlt(hMemDC, 0, 0, bm.bmWidth, bm.bmHeight,
                    hDC, 0, 0, SRCCOPY);
                  DWORD MaxRects = MAX_ALLOC_RECTS;
                  SYSTEM_INFO  Sysinfo;
                  //get memory size
                  GetSystemInfo(&Sysinfo);
                  //make a stack that can change big
                  //allocate memory
                  HANDLE hRcData=HeapCreate(HEAP_GENERATE_EXCEPTIONS,
                      Sysinfo.dwPageSize, 0);
                  RGNDATA * pRcData=(RGNDATA*)HeapAlloc
                      (hRcData,HEAP_ZERO_MEMORY,
                      sizeof(RGNDATAHEADER)+sizeof(RECT)*MaxRects);
                      //fill the the RGNDATA struct
                  pRcData->rdh.dwSize = sizeof(RGNDATAHEADER);
                  pRcData->rdh.iType = RDH_RECTANGLES;
                  pRcData->rdh.nCount =
                      pRcData->rdh.nRgnSize = 0;
                  SetRect(&pRcData->rdh.rcBound, MAXLONG,
                      MAXLONG, 0, 0);
                        BYTE hr,hg,hb,lr,lg,lb;
                  switch(BkColor)
                  {
                  case RGB(255,255,255):  //if the bkcolor is white
                    hr = GetRValue(BkColor);
                    hg = GetGValue(BkColor);
                    hb = GetBValue(BkColor);
                    lr = min(0xff, hr - GetRValue(Tolerance));
                    lg = min(0xff, hg - GetGValue(Tolerance));
                    lb = min(0xff, hb - GetBValue(Tolerance));
                    break;
                  case RGB(0,0,0):  //if the bkcolor is black
                    lr = GetRValue(BkColor);
                    lg = GetGValue(BkColor);
                    lb = GetBValue(BkColor);
                    hr = min(0xff, lr + GetRValue(Tolerance));
                    hg = min(0xff, lg + GetGValue(Tolerance));
                    hb = min(0xff, lb + GetBValue(Tolerance));
                    break;
                  default:        //if the bkcolor is other color
                    Tolerance=0x111111;
                    lr =max(0, GetRValue(BkColor)
                       -GetRValue(Tolerance));
                    lg = max(0,GetGValue(BkColor)
                       -GetGValue(Tolerance));
                    lb = max(0,GetBValue(BkColor)
                       -GetBValue(Tolerance));
                    hr=min(0xff,GetRValue(BkColor)
                      +GetRValue(Tolerance));
                    hg=min(0xff,GetGValue(BkColor)
                      +GetGValue(Tolerance));
                    hb=min(0xff,GetBValue(BkColor)
                      +GetBValue(Tolerance));
                    break;
                  }
                  // Get the bit point and do the search
                  BYTE *pBits = (BYTE *)bm32.bmBits +
                      (bm32.bmHeight - 1) * bm32.bmWidthBytes;
                  for (int y = 0; y < bm.bmHeight; y++)
                  {
                    for (int x = 0; x < bm.bmWidth; x++)
                    {
                      int x0 = x;
                      DWORD *pColor = (DWORD *)pBits + x;
                      BYTE dr,dg,db;
                      while (x < bm.bmWidth)
                      {
                        dr=GetRValue(*pColor);
                        dg=GetGValue(*pColor);
                        db=GetBValue(*pColor);

                        if ((dr>= lr && dr<= hr) && (dg>=lg&&dg<=hg)
                             && (db>=lb&&db<=hb))
                          {
                            if(Direct)
                              break;
                              else
                              {
                                pColor++;
                                x++;
                                }
                              }
                              else if(Direct)
                              {
                                pColor++;
                                x++;
                              }
                              else
                                break;

                              }
                              if (x > x0)
                              {
                                if (pRcData->rdh.nCount >= MaxRects)
                                {
                                  MaxRects += MAX_ALLOC_RECTS;
                                  //re alloc the stack
                                  pRcData=(RGNDATA*)HeapReAlloc(
                                  hRcData,HEAP_ZERO_MEMORY,pRcData, 
                                  sizeof(RGNDATAHEADER)+sizeof(RECT)
                                     *MaxRects);
                                }
                                RECT *pr = (RECT *)&pRcData->Buffer;
                                SetRect(&pr[pRcData->rdh.nCount],
                                        x0, y, x, y+1);
                                pRcData->rdh.rcBound.left = x0;
                                pRcData->rdh.rcBound.top = y;
                                pRcData->rdh.rcBound.right = x;
                                pRcData->rdh.rcBound.bottom = y+1;
                                pRcData->rdh.nCount++;

                                if (pRcData->rdh.nCount == 3000)
                                {
                                  HRGN tmphRgn = ExtCreateRegion(NULL,
                                  sizeof(RGNDATAHEADER) +
                                        (sizeof(RECT)
                                     * MaxRects),
                                  pRcData);
                                  if (hRgn)
                                  {
                                    CombineRgn(hRgn, hRgn, tmphRgn,
                                               RGN_OR);
                                    DeleteObject(tmphRgn);
                                  }
                                  else
                                    hRgn = tmphRgn;
                                    pRcData->rdh.nCount = 0;
                                    SetRect(&pRcData->rdh.rcBound,
                                    MAXLONG, MAXLONG, 0, 0);
                              }
                            }
                        }

                        // search next line
                        pBits -= bm32.bmWidthBytes;
                    }
                    HRGN tmphRgn = ExtCreateRegion(NULL,
                        sizeof(RGNDATAHEADER) + (sizeof(RECT)
                            * MaxRects), pRcData);
                    if (hRgn)
                    {
                      CombineRgn(hRgn, hRgn, tmphRgn, RGN_OR);
                      DeleteObject(tmphRgn);
                    }
                    else
                      hRgn = tmphRgn;
                      // make a rect, use this rect xor to the
                      // BkColor then we can get the rect we want
                    if(!Direct)
                    {
                      HRGN hRect=CreateRectRgn(0,0,bm.bmWidth,
                                               bm.bmHeight);
                        if(hRect)
                        {
                          CombineRgn(hRgn,hRgn,hRect,RGN_XOR);
                          DeleteObject(hRect);
                        }
                        else
                          return NULL;
                    }
                    //release the memory
                    HeapFree(hRcData,HEAP_NO_SERIALIZE,pRcData);
                    SelectObject(hDC, holdBmp);
                    DeleteDC(hDC);
                    DeleteObject(holdBmp);
                }
                SelectObject(hMemDC,hOldib32);
                DeleteDC(hMemDC);
                DeleteObject(hOldib32);
                DeleteObject(hDib32);
            }
            else
                DeleteDC(hMemDC);
        }
    }
    return hRgn;
  }

Add a handler for the ON_WM_ERASEBKND message to erase the dialog's background:

BOOL CSkinDlg::OnEraseBkgnd(CDC* pDC)
{
  if(m_hBmp)
  {
    BITMAP bm;
    GetObject(m_hBmp,sizeof(bm),&bm);
    HDC hMemdc=CreateCompatibleDC(pDC->m_hDC);
    if(hMemdc)
    {
      HBITMAP hOldBmp=(HBITMAP)SelectObject(hMemdc,m_hBmp);
        if(hOldBmp)
        {
          BitBlt(pDC->m_hDC,
                 0,0,
                 bm.bmWidth,
                 bm.bmHeight,
                 hMemdc,
                 0,0,
                 SRCCOPY);
          SelectObject(hMemdc,hOldBmp);
          DeleteDC(hMemdc);
          DeleteObject(hOldBmp);
          return TRUE;
        }
        else
          DeleteDC(hMemdc);
      }
  }
  return CDialog::OnEraseBkgnd(pDC);
}

In your OnInitDialog, enter the following code:

BOOL CSkinDlg::OnInitDialog()
{
  .
  .
  .
  // Show the Skin
  if(m_hWndRgn)
    SetWindowRgn(m_hWndRgn,TRUE);

  return TRUE;  // return TRUE unless you set the focus to a control
}

The Minimise and Close boxes on the dialog are implemented using Davide Calabro's CButtonST class.

That's it! Run your app and you will see your great skin. This article is provided by www.codefinger.de.

Downloads

Download demo project - 52 Kb