客户区贴图的问题

/ 对话框位图背景  - WM_CTLCOLORDLG中使用StretchBlt贴图
//By MoreWindows-(http://blog.)
#include <windows.h>
#include "resource.h"

const char szDlgTitle[] = "位图背景 使用StretchBlt贴图 MoreWindows-(http://blog.)";

// 对话框消息处理函数
BOOL CALLBACK DlgProc(HWND hDlg, UINT message, WPARAM wParam, LPARAM lParam);
         
int APIENTRY WinMain(HINSTANCE hInstance,
                     HINSTANCE hPrevInstance,
                     LPSTR     lpCmdLine,
                     int       nCmdShow)
{
    DialogBox(hInstance, MAKEINTRESOURCE(IDD_DIALOG1), NULL, DlgProc);
    return 0;
}


BOOL CALLBACK DlgProc(HWND hDlg, UINT message, WPARAM wParam, LPARAM lParam)
{
    RECT       rcDialog;
    HBITMAP    hBitmap;
    static BITMAP s_bm;
    static HDC    s_hdcMem;

    switch (message)
    {
    case WM_INITDIALOG:
        // 设置对话框标题
        SetWindowText(hDlg, szDlgTitle);
        // 设置对话框大小可调节
        SetWindowLong(hDlg, GWL_STYLE, GetWindowLong(hDlg, GWL_STYLE) | WS_SIZEBOX);

        // 加载背影图片
        hBitmap = (HBITMAP)LoadImage(NULL, "005.bmp", IMAGE_BITMAP, 0, 0, LR_LOADFROMFILE | LR_CREATEDIBSECTION);
        if (hBitmap == NULL)
        {
            MessageBox(hDlg, "LoadImage failed", "Error", MB_ICONERROR);
            exit(0);
        }      
        else
        {
            // 将背影图片放入HDC - s_hdcMem
            HDC        hdc;
            hdc = GetDC(hDlg);
            s_hdcMem = CreateCompatibleDC(hdc);
            SelectObject(s_hdcMem, hBitmap);   
            ReleaseDC(hDlg, hdc);

            // 得到位图信息
            GetObject(hBitmap, sizeof(s_bm), &s_bm);
        }

        return 0;

    case WM_COMMAND:
        switch (LOWORD(wParam))
        {
        case IDCANCEL:
            DeleteDC(s_hdcMem);
            EndDialog(hDlg, LOWORD(wParam));
            return TRUE;
        }
        break;


    case WM_SIZE:
        InvalidateRect(hDlg, NULL, TRUE);
        return TRUE;

    case WM_CTLCOLORDLG:
        GetClientRect(hDlg, &rcDialog);
        //通过SetStretchBltMode的设置能使StretchBlt在缩放图像更加清晰
        SetStretchBltMode((HDC)wParam, COLORONCOLOR);
        StretchBlt((HDC)wParam, 0, 0, rcDialog.right, rcDialog.bottom, s_hdcMem, 0, 0, s_bm.bmWidth, s_bm.bmHeight, SRCCOPY);   
        return (BOOL)((HBRUSH)GetStockObject(NULL_BRUSH));
    }
    return FALSE;
}

.386
.model flat, stdcall  ;32 bit memory model
option casemap :none  ;case sensitive

include test.inc

.code

start:
    invoke    GetModuleHandle,NULL
    mov    hInstance,eax
    invoke    InitCommonControls
    invoke    DialogBoxParam,hInstance,IDD_MAIN,NULL,addr DlgProc,NULL
    invoke    ExitProcess,0

;########################################################################

DlgProc    proc    hWin:HWND,uMsg:UINT,wParam:WPARAM,lParam:LPARAM
    LOCAL hdc:HDC
    LOCAL hdcSrc:HDC
    LOCAL PicH:DWORD
    LOCAL PicW:DWORD
    LOCAL rect:RECT
    LOCAL hRgn:HRGN
    LOCAL hbitmap:HBITMAP
    LOCAL sbmp:BITMAP
    LOCAL hpaint:PAINTSTRUCT
   
    mov    eax,uMsg
    .if    eax==WM_INITDIALOG
        invoke GetWindowLong,hWin, GWL_STYLE
        or eax,WS_SIZEBOX
        invoke SetWindowLong,hWin,GWL_STYLE,eax
        invoke LoadBitmap,hInstance,logo
        mov hbitmap,eax
        invoke GetDC,hWin
        mov hdc,eax
        invoke CreateCompatibleDC,hdc
        mov hdcSrc,eax
        invoke SelectObject,hdcSrc,hbitmap
        invoke GetObject,hbitmap,sizeof sbmp,addr sbmp
        invoke ReleaseDC,hWin,hdc
        ;initialization here
    .elseif eax==WM_CTLCOLORDLG
        invoke GetClientRect,hWin,addr rect
        invoke SetStretchBltMode,wParam,COLORONCOLOR
        invoke StretchBlt,wParam,0,0,rect.right,rect.bottom,hdcSrc,0,0,sbmp.bmWidth,sbmp.bmHeight,SRCCOPY
        invoke GetStockObject,NULL_BRUSH
;        ret
    .elseif    eax==WM_SIZE
        invoke InvalidateRect,hWin,NULL,TRUE
;        mov eax,TRUE
;        ret
    .elseif    eax==WM_COMMAND
        mov edx,wParam
        movzx eax,dx
        shr edx,16
        .if edx==BN_CLICKED
            .if eax==IDOK

            .elseif eax==IDCANCEL
                invoke    SendMessage,hWin,WM_CLOSE,NULL,NULL
            .endif
        .endif
    .elseif    eax==WM_CLOSE
        invoke    EndDialog,hWin,0
    .else
        mov    eax,FALSE
        ret
    .endif
    mov    eax,TRUE
    ret
DlgProc endp

end start