win32 窗口 自定义坐标系 绘制表盘

win32 窗口 自定义坐标系 绘制表盘
测试环境: win7 64 位 vs2013

建立一个 win32 应用程序 ，空项目，名称是 HelloDrawClockFace,
在项目中添加源文件 HelloDrawClockFace.cpp :

内容如下:

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

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

int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance,
    PSTR szCmdLine, int iCmdShow)
{
    static TCHAR szAppName[] = TEXT("HelloWin");
    HWND         hwnd;
    MSG          msg;
    WNDCLASS     wndclass;

    wndclass.style = CS_HREDRAW | CS_VREDRAW;
    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 = (HBRUSH)GetStockObject(WHITE_BRUSH);
    wndclass.lpszMenuName = NULL;
    wndclass.lpszClassName = szAppName;

    if (!RegisterClass(&wndclass))
    {
        MessageBox(NULL, TEXT("This program requires Windows NT!"),
            szAppName, MB_ICONERROR);
        return 0;
    }

    hwnd = CreateWindow(szAppName,                  // window class name
        TEXT("The Hello Program"), // window caption
        WS_OVERLAPPEDWINDOW,        // window style
        CW_USEDEFAULT,              // initial x position
        CW_USEDEFAULT,              // initial y position
        CW_USEDEFAULT,              // initial x size
        CW_USEDEFAULT,              // initial y size
        NULL,                       // parent window handle
        NULL,                       // window menu handle
        hInstance,                  // program instance handle
        NULL);                     // creation parameters

    ShowWindow(hwnd, iCmdShow);
    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;

    switch (message)
    {
    case WM_CLOSE:

        DestroyWindow(hwnd);

        break;

    case WM_DESTROY:

        PostQuitMessage(0);

        break;

    case WM_PAINT:{                                             //1

        hdc = BeginPaint(hwnd, &ps);                            //2

        RECT rect;                                              //3

        GetClientRect(hwnd, &rect);                             //4

        int cx = rect.right - rect.left;                        //5

        int cy = rect.bottom - rect.top;                        //6


        SetMapMode(hdc, MM_ISOTROPIC);                          //7

        SetWindowExtEx(hdc, 1000, 1000, NULL);                  //8

        SetViewportExtEx(hdc, cx, -cy, NULL);                   //9

        SetViewportOrgEx(hdc, cx/2, cy/2, NULL);                //10


        static POINT pt[] = {                                   //11
            0,300,                                              //12
            300,0,                                              //13            
            0, -300,                                            //14
            -300, 0,                                            //15
        };                                                      //16

        for (int i = 0; i < 4; i++){                            //17

            Ellipse(hdc, pt[i].x - 20,                          //18
                         pt[i].y + 20,                          //19
                         pt[i].x + 20,                          //20
                         pt[i].y - 20 );                        //21
        }                                                       //22


        EndPaint(hwnd, &ps);                                    //23

        break;                                                  //24
    }                                                           //25

    default:

        return DefWindowProc(hwnd, message, wParam, lParam);

    }

    return 0;
}

运行效果如下:

设置之后的坐标系:

重点看:

1.坐标原点位置的修改

2.x轴与y轴方向的修改

3.逻辑尺寸与实际尺寸的映射

4.MM_ISOTROPIC 模式 图形的形状不会变化，只是放大和缩小，不会拉伸变形

如下图: