一个风车程序里的难处
//源程序如下
#include <windows.h>
#include <stdlib.h>
#include <string.h>
#include <math.h>
#define PI 3.1415926
int nNum=0,nMaxNum=20;//我不知道，为什么有这两个变量
LRESULT CALLBACK WindowProc(
HWND hwnd,
// handle to window
UINT uMsg,
// message identifier
WPARAM wParam,
// first message parameter
LPARAM lParam
// second message parameter
);
int WINAPI WinMain(
HINSTANCE hInstance,
// handle to current instance
HINSTANCE hPrevInstance,
// handle to previous instance
LPSTR lpCmdLine,
// command line
int nCmdShow
// show state
)
{
HWND hwnd;
MSG Msg;
WNDCLASS wndclass;
wndclass.cbClsExtra=0;
wndclass.cbWndExtra=0;
wndclass.hbrBackground=(HBRUSH)GetStockObject(WHITE_BRUSH);
wndclass.hCursor=LoadCursor(NULL,IDC_ARROW);
wndclass.hIcon=LoadIcon(NULL,IDI_APPLICATION);
wndclass.hInstance=hInstance;
wndclass.lpfnWndProc=WindowProc;
wndclass.lpszClassName="abc";
wndclass.lpszMenuName=NULL;
wndclass.style=0;
RegisterClass(&wndclass);
hwnd=CreateWindow("abc","旋转的风车",WS_OVERLAPPEDWINDOW,CW_USEDEFAULT,0,600,450,NULL,NULL,hInstance,NULL);
ShowWindow(hwnd,SW_SHOWNORMAL);
UpdateWindow(hwnd);
while(GetMessage(&Msg,hwnd,NULL,0))
{
TranslateMessage(&Msg);
DispatchMessage(&Msg);
}
return 0;
}
LRESULT CALLBACK WindowProc(
HWND hwnd,
// handle to window
UINT uMsg,
// message identifier
WPARAM wParam,
// first message parameter
LPARAM lParam
// second message parameter
)
{
HDC hdc;
HBRUSH hBrush;
HPEN hp;
PAINTSTRUCT ps;
int nCenterX,nCenterY;
double fAngle;
switch(uMsg)
{
case WM_PAINT:
hdc=BeginPaint(hwnd,&ps);
SetMapMode(hdc,MM_ANISOTROPIC);
SetWindowExtEx(hdc,400,300,NULL);
SetViewportExtEx(hdc,600,450,NULL);
SetViewportOrgEx(hdc,300,200,NULL);
//
绘制外圆
hp=CreatePen(PS_SOLID,1,RGB(255,0,255));
SelectObject(hdc,hp);
Ellipse(hdc,-100,-100,100,100);
//
绘制风车的叶片
//
绘制红色的叶片
hBrush=CreateSolidBrush(RGB(255,0,0));
SelectObject(hdc,hBrush);
fAngle=2*PI/nMaxNum*nNum;//这里也看不懂
，fangle，实现了什么功能？
nCenterX=(int)(50*cos(fAngle));
nCenterY=(int)(50*sin(fAngle));
Pie(hdc,nCenterX-50,nCenterY-50,nCenterX+50,nCenterY+50,(int)(nCenterX+50*cos(fAngle)),(int)(nCenterY+50*sin(fAngle)),(int)(nCenterX+50*cos(fAngle+PI)),(int)(nCenterY+50*sin(fAngle+PI)));//上面的pie画图函数的参数，用正弦，余弦，为什么要用这两个函数，实现了什么功能呢？
//
绘制蓝色的叶片
hBrush=CreateSolidBrush(RGB(255,255,0));
SelectObject(hdc,hBrush);
nCenterX=(int)(50*cos(fAngle+2*PI/3));
nCenterY=(int)(50*sin(fAngle+2*PI/3));
Pie(hdc,nCenterX-50,nCenterY-50,nCenterX+50,nCenterY+50,(int)(nCenterX+50*cos(fAngle+2*PI/3)),(int)(nCenterY+50*sin(fAngle+2*PI/3)),(int)(nCenterX+50*cos(fAngle+PI+2*PI/3)),(int)(nCenterY+50*sin(fAngle+PI+2*PI/3)));
//
绘制黄色的叶片
hBrush=CreateSolidBrush(RGB(0,255,255));
SelectObject(hdc,hBrush);
nCenterX=(int)(50*cos(fAngle+4*PI/3));
nCenterY=(int)(50*sin(fAngle+4*PI/3));
Pie(hdc,nCenterX-50,nCenterY-50,nCenterX+50,nCenterY+50,(int)(nCenterX+50*cos(fAngle+4*PI/3)),(int)(nCenterY+50*sin(fAngle+4*PI/3)),(int)(nCenterX+50*cos(fAngle+PI+4*PI/3)),(int)(nCenterY+50*sin(fAngle+PI+4*PI/3)));
nNum++;//这个实现了什么？
Sleep(100);//这个实现了什么？
InvalidateRect(hwnd,NULL,1);
EndPaint(hwnd,&ps);
return 0;
case WM_CLOSE:
PostQuitMessage(0);
break;
default:
return DefWindowProc(hwnd,uMsg,wParam,lParam);
}
return 0;
}
这个程序实现了，旋转的风车，但是有的看不懂，请大侠帮忙看一下，谢拉
