#include<windows.h>
#include<string.h>
#include<stdlib.h>
#include<stdio.h>

 LRESULT CALLBACK WndProc (HWND,UINT, WPARAM,LPARAM);

 int WINAPI WinMain (HINSTANCE hInstance,
                     HINSTANCE hPrevlnst,
                    LPSTR lpszCmdLine,int nCmdShow)
{
    HWND hwnd;
    MSG Msg;
    WNDCLASS wndclass;
    char lpszClassName[]="映射模式";
    char lpszTitle[]="映射模式";
    wndclass.style=0;
    wndclass.lpfnWndProc=WndProc;
    wndclass.cbClsExtra=0;
    wndclass.cbWndExtra=0;
    wndclass.hInstance=hInstance;
    wndclass.hIcon=LoadIcon(NULL,IDI_APPLICATION);
    wndclass.hCursor=LoadCursor(NULL,IDC_ARROW);
    wndclass.hbrBackground= GetStockObject(WHITE_BRUSH);
    wndclass.lpszMenuName=NULL;
    wndclass.lpszClassName=lpszClassName;

    if(!RegisterClass(&wndclass))
    {
        MessageBeep(0);
        return FALSE;
    }
    hwnd=CreateWindow ( lpszClassName,
                        lpszTitle,
                        WS_OVERLAPPEDWINDOW,
                        CW_USEDEFAULT,
                        CW_USEDEFAULT,
                        CW_USEDEFAULT,
                        CW_USEDEFAULT,
                        NULL,
                        NULL,
                        hInstance,
                        NULL
                        );

    ShowWindow(hwnd,nCmdShow);
    UpdateWindow(hwnd);

    while (GetMessage(&Msg,NULL,0,0))
        {
            TranslateMessage(&Msg);
            DispatchMessage(&Msg);
        }
        return Msg.wParam;
    }

    LRESULT CALLBACK WndProc ( HWND hwnd,
                               UINT message,
                               WPARAM wParam,
                               LPARAM lParam
                            )
    {
        HDC hdc;
        PAINTSTRUCT ps;
        //HPEN hP;
        HBRUSH hB1,hB2;
        int nMode;
        switch(message)
        {
            case WM_CREATE:
                nMode=MM_TEXT;
            case WM_LBUTTONDOWN:
                nMode=MM_ISOTROPIC;
                //nMode=MM_LOMETRIC;
                InvalidateRect(hwnd,NULL,1);
                break;
            case WM_RBUTTONDOWN:
                nMode=MM_ANISOTROPIC;
                InvalidateRect(hwnd,NULL,1);
                break;
            case WM_PAINT:
                //hP=CreatePen(PS_DASHDOT,1,RGB(0,0,255));
                //hB=CreateHatchBrush(HS_CROSS,RGB(0,255,0));
                hdc=BeginPaint(hwnd,&ps);
                SetMapMode(hdc,nMode);
                SetWindowExtEx(hdc,150,150,NULL);
                SetViewportExtEx(hdc,150,100,NULL);
                //SetViewportOrgEx(hdc,150,60,NULL);


                hB1=GetStockObject(BLACK_BRUSH);
                hB2=GetStockObject(WHITE_BRUSH);
                SelectObject(hdc,hB1);
                Rectangle(hdc,0,0,150,150);
                SelectObject(hdc,hB2);
                Ellipse(hdc,0,0,150,150);
                EndPaint(hwnd,&ps);
                break;
            case WM_DESTROY:
                DeleteObject(hB1);
                DeleteObject(hB2);
                PostQuitMessage(0);
                break;
            default:
                return DefWindowProc(hwnd,message,wParam,lParam);
        }
        return 0;
    }

初学win32编程，上面程序是通过左击和右击改变映射模式的，可是运行后发现没改变，不知道问题在哪？求大神帮忙看看

[ 本帖最后由 zcl2013c 于 2014-3-4 16:41 编辑 ]

WM_CREATE 后面丢了 break;

另外 你的 nMode 是局部变量

谢谢指教
还麻烦请教
1、nMode不是只在wndproc函数下需要么，为何要改为全局变量？
2、WM_CREATE,WM_LBUTTONDOWN,WM_RBUTTONDOWN消息后为何一定要加break？例如createwindow函数产生WM_CREATE消息，映射模式为MM_TEXT,不加break继续判断消息，因为未进行WM_LBUTTONDOWN和WM_RBUTTONDOWN操作，所以等待updatewindow产生WM_PAINT消息，进行MM_TEXT映射。可是程序结果是变为MM_ANISOTROPIC映射？不知我的理解哪里错误，还请指导下

系统根据你的操作调用WinProc函数，并发送相应消息

每次发的消息都会调用一次WinProc，简单说就是，WinProc被多次调用。

你的nMode是局部变量，每次执行WinProc ，这多个 nMode 间没有联系

所以要设为 静态变量，当然全局变量也是可以的

至于为何加 break ？  给你这段代码

int a = 0；
switch (a)
{
case 0:
  a = 0;
case 1:
  a = 1;
  break;
case 2;
  a = 2;
  break;
default:
}

谢谢，是我理解错了switch