练习GDI画图函数

参考《windows程序设计》第五章，5-3 LINEDEMO.C， 此程序仅作为练习使用。
先看一下运行结果：

程序源代码：

/*
 * 这个程序是作为练习windows GDI画图函数而用的， by netrookie
 * 请参考《windows程序设计》第五章，图形基础
 */
#include <windows.h>

LRESULT CALLBACK WndProc(HWND, UINT, WPARAM, LPARAM);
int WINAPI WinMain(HINSTANCE hInstance,
                 HINSTANCE hPrevInstance,
                 PSTR szCmdLine,
                 int iCmdShow) {
    static TCHAR szAppName[] = TEXT("draw");
    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 = GetStockObject(WHITE_BRUSH);
    wndclass.lpszMenuName = NULL;
    wndclass.lpszClassName = szAppName;

    if(!RegisterClass(&wndclass)) {
        MessageBox(NULL, TEXT("Register failure..."),
            szAppName, MB_ICONERROR);
        return 0;
    }

    hwnd = CreateWindow(szAppName,
        szAppName,
        WS_OVERLAPPEDWINDOW,
        CW_USEDEFAULT,
        CW_USEDEFAULT,
        CW_USEDEFAULT,
        CW_USEDEFAULT,
        NULL,
        NULL,
        hInstance,
        NULL);

    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) {
    static int cxClient, cyClient;
    PAINTSTRUCT ps;
    HDC hdc;
    POINT pt[5];

    switch(message) {
    case WM_SIZE:
        cxClient = LOWORD(lParam);
        cyClient = HIWORD(lParam);
        return 0;

    case WM_PAINT:
        hdc = BeginPaint(hwnd, &ps);

        // 画横线

        MoveToEx(hdc, 0, cyClient / 2, NULL);
        LineTo(hdc, cxClient, cyClient / 2);

        // 画竖线

        MoveToEx(hdc, cxClient / 2, 0, NULL);
        LineTo(hdc, cxClient / 2, cyClient);

        // 画平行四边形

        pt[0].x = cxClient / 4;
        pt[0].y = 0;
        pt[1].x = cxClient / 2;
        pt[1].y = cyClient / 4;
        pt[2].x = cxClient / 4;
        pt[2].y = cyClient / 2;
        pt[3].x = 0;
        pt[3].y = cyClient / 4;
        pt[4].x = cxClient / 4;
        pt[4].y = 0;
    
        Polyline(hdc, pt, 5);

        // 画椭圆

        Ellipse(hdc, cxClient / 2, 0, cxClient, cyClient / 2);

        // 画圆矩形

        RoundRect(hdc, cxClient / 8, 5 * cyClient / 8,
            cxClient / 2 - cxClient / 8, cyClient - cyClient / 8,
            cxClient / 16, cyClient / 16);

        // 画弦

        Chord(hdc, cxClient / 2, cyClient / 2, 3 * cxClient / 2, 3* cyClient / 2,
            cxClient, cyClient / 2, cxClient / 2, cyClient);

        EndPaint(hwnd, &ps);
        return 0;

    case WM_DESTROY:
        PostQuitMessage(0);
        return 0;
    }
    return DefWindowProc(hwnd, message, wParam, lParam);
}