实现三角形沿一条斜线下滑，并在下滑的过程中逆时钟旋转三角形

Question

从窗口客户区的左上角向右下角下滑，在下滑过程中，三角形做逆时钟旋转，到达右下角时，正好以一条底边和客户区边框重合并停止，在改变窗口大小时，停止三角形的下落，重新从左上角开始下落。

Answer 1

#include <windows.h>
#include <math.h>#define   PI   3.1415926
#define   ID_TIMER   1000LRESULT CALLBACK WndProc(HWND,UINT,WPARAM,LPARAM);
void DrawTriangle(HDC hdc,int r,int angle);int WINAPI WinMain(HINSTANCE hInstance,HINSTANCE hPrevInstance,LPSTR szCmdLine,int iCmdShow)
{
static TCHAR szAppName[] = TEXT("Triangle");
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(BLACK_BRUSH);
wndclass.lpszMenuName = NULL;
wndclass.lpszClassName = szAppName; if (!RegisterClass (&wndclass))
{
MessageBox(NULL,TEXT("窗口类注册失败!"),szAppName,MB_ICONERROR);
return 0;
} hWnd = CreateWindow(szAppName,TEXT("旋转的三角形"),
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)
{
HDC hdc,hMem;
HBITMAP     hBitmap;
PAINTSTRUCT ps;
RECT        rect;
BOOL        back;
static  int    r,angle;
static  POINT  pos;
static  int    width,height;
static  double grade;      
switch ( message )
{
case WM_SIZE:
GetClientRect(hWnd,&rect);
width  = rect.right  - rect.left;
height = rect.bottom - rect.top;
r      = (int)(sqrt(pow((double)width,2.0) + pow((double)height,2.0)) / 20.0);
angle  = 0;
grade  = atan((double)height / width);
pos.x  = pos.y = r;
return 0;
case WM_CREATE:
SetTimer(hWnd,ID_TIMER,100,NULL);
return 0;
case WM_TIMER:
angle = (angle + 20) % 360;
pos.x += r * 0.5 * cos(grade);
pos.y += r * 0.5 * sin(grade);
InvalidateRect(hWnd,NULL,FALSE);
return 0; case WM_PAINT:
hdc = BeginPaint(hWnd,&ps);
GetClientRect(hWnd,&rect);

hBitmap = CreateCompatibleBitmap(hdc,width,height);
hMem    = CreateCompatibleDC(hdc);
SelectObject(hMem,hBitmap); SelectObject(hMem,GetStockObject(BLACK_BRUSH));
Rectangle(hMem,rect.left,rect.top,rect.right,rect.bottom); SetMapMode(hMem,MM_ANISOTROPIC);
SetViewportExtEx(hMem,width,height,NULL);
SetWindowExtEx(hMem,width,-height,NULL); back = FALSE;
if (pos.x + r * 0.866 > width || pos.y + r * 0.5 > height) 
{
//pos.x = width - r * 0.866;
//pos.y = height - r * 0.5;
angle = 0;
back  = TRUE;
}
SetViewportOrgEx(hMem,pos.x,pos.y,NULL); DrawTriangle(hMem,r,angle); SetMapMode(hMem,MM_TEXT);
SetViewportOrgEx(hMem,0,0,NULL); BitBlt(hdc,0,0,width,height,hMem,0,0,SRCCOPY); DeleteDC(hMem);
DeleteObject(hBitmap);
EndPaint(hWnd,&ps);
if (back)
{
pos.x = pos.y = r;
angle = 0;
Sleep(500);
}
return 0; case WM_DESTROY :
PostQuitMessage(0);
return 0;
}
return DefWindowProc(hWnd,message,wParam,lParam);
}void DrawTriangle(HDC hdc,int r,int angle)
{
POINT   A,B,C;
HPEN    hPen;
HBRUSH  hBrush; A.x = (long)(r * cos(((90 + angle)  % 360) * PI / 180));
A.y = (long)(r * sin(((90 + angle)  % 360) * PI / 180)); B.x = (long)(r * cos(((210 + angle) % 360) * PI / 180));
B.y = (long)(r * sin(((210 + angle) % 360) * PI / 180)); C.x = (long)(r * cos(((330 + angle) % 360) * PI / 180));
C.y = (long)(r * sin(((330 + angle) % 360) * PI / 180)); hPen = CreatePen(PS_SOLID,1,RGB(255,255,0));
hBrush = CreateSolidBrush(RGB(255,255,0));
SelectObject(hdc,hPen);
SelectObject(hdc,hBrush); MoveToEx(hdc,A.x,A.y,NULL);
LineTo(hdc,B.x,B.y);
LineTo(hdc,C.x,C.y);
LineTo(hdc,A.x,A.y);
FloodFill(hdc,0,0,RGB(255,255,0)); DeleteObject(SelectObject(hdc,GetStockObject(WHITE_BRUSH)));
DeleteObject(SelectObject(hdc,GetStockObject(GRAY_BRUSH)));
}