CLOVER程式发表评论(0)编辑词条

    要用常规的方法画出这个图形，就必须根据椭圆的边线公式计算出每条直线的端点。利用复杂的剪裁区域，可以直接画出这些线条，而让Windows确定其端点。CLOVER如程式5-8所示。

CLOVER程式-说明    程式5-8  CLOVER
CLOVER.C
/*--------------------------------------------------------------------------
        CLOVER.C --        Clover Drawing Program Using Regions
                        (c) Charles Petzold, 1998
----------------------------------------------------------------------*/
#include <windows.h>
#include <math.h>

#define TWO_PI (2.0 * 3.14159)
LRESULT CALLBACK WndProc (HWND, UINT, WPARAM, LPARAM) ;
int WINAPI WinMain (HINSTANCE hInstance, HINSTANCE hPrevInstance,
                          PSTR szCmdLine, int iCmdShow)
{
        static TCHAR szAppName【】 = TEXT ("Clover") ;
        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, TEXT ("Draw a Clover"),
                                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 iMsg, WPARAM wParam, LPARAM lParam)
{
        static HRGN hRgnClip ;
        static int        cxClient, cyClient ;
        double        fAngle, fRadius ;
        HCURSOR        hCursor ;
        HDC                 hdc ;
        HRGN                 hRgnTemp【6】 ;
        int                i ;
        PAINTSTRUCT ps ;
        switch (iMsg)
        {
        case        WM_SIZE:
                cxClient        = LOWORD (lParam) ;
                cyClient        = HIWORD (lParam) ;
                hCursor        = SetCursor (LoadCursor (NULL, IDC_WAIT)) ;
                ShowCursor (TRUE) ;
         
                if (hRgnClip)
                        DeleteObject (hRgnClip) ;
         
                hRgnTemp【0】        = CreateEllipticRgn (0, cyClient / 3,
                                                cxClient / 2, 2 * cyClient / 3) ;
                hRgnTemp【1】        = CreateEllipticRgn (cxClient / 2, cyClient / 3,
                                                cxClient, 2 * cyClient / 3) ;
                hRgnTemp【2】        = CreateEllipticRgn (cxClient / 3, 0,
                                                2 * cxClient / 3, cyClient / 2) ;
                hRgnTemp【3】        = CreateEllipticRgn (cxClient / 3, cyClient / 2,
2 * cxClient / 3, cyClient) ;
                hRgnTemp【4】        = CreateRectRgn (0, 0, 1, 1) ;
                hRgnTemp【5】        = CreateRectRgn (0, 0, 1, 1) ;
                hRgnClip        = CreateRectRgn (0, 0, 1, 1) ;

                CombineRgn (hRgnTemp【4】, hRgnTemp【0】, hRgnTemp【1】, RGN_OR) ;
                CombineRgn (hRgnTemp【5】, hRgnTemp【2】, hRgnTemp【3】, RGN_OR) ;
                CombineRgn (hRgnClip,    hRgnTemp【4】, hRgnTemp【5】, RGN_XOR) ;
         
                for (i = 0 ; i < 6 ; i++)
                        DeleteObject (hRgnTemp) ;
         
                SetCursor (hCursor) ;
                ShowCursor (FALSE) ;
                return 0 ;
         
        case        WM_PAINT:
                hdc = BeginPaint (hwnd, &ps) ;
         
                SetViewportOrgEx (hdc, cxClient / 2, cyClient / 2, NULL) ;
          SelectClipRgn (hdc, hRgnClip) ;
                fRadius = _hypot (cxClient / 2.0, cyClient / 2.0) ;
                for (fAngle = 0.0 ; fAngle < TWO_PI ; fAngle += TWO_PI / 360)
                {
                        MoveToEx (hdc, 0, 0, NULL) ;
                        LineTo (hdc,        (int) ( fRadius * cos (fAngle) + 0.5),
                                (int) (-fRadius * sin (fAngle) + 0.5)) ;
                }
                EndPaint (hwnd, &ps) ;
                return 0 ;
        case WM_DESTROY:
                DeleteObject (hRgnClip) ;
                PostQuitMessage (0) ;
                return 0 ;
        }
        return DefWindowProc (hwnd, iMsg, wParam, lParam) ;
}