#include "TLines.h"


static const int vRange = 12;    //速度變化范圍
static const int scrwth=GetSystemMetrics(SM_CXFULLSCREEN);   //窗口寬度
static const int scrhgt=GetSystemMetrics(SM_CYFULLSCREEN)+40;//窗口高度


void TLines::Draw(HWND hwnd)  //畫線,整個程序寫的最關鍵函數(shù)
{
   int i,j;   //定義兩個計數(shù)器
   HDC hdc;   //Windows系統(tǒng)類型,窗口的設備環(huán)境
   HPEN oldpen,newpen,ReverseNewPen;  //Windows系統(tǒng)類型,畫筆   

   //獲取該窗口的設備環(huán)境
   hdc=GetDC(hwnd);

   newpen=CreatePen(PS_SOLID,1,RGB(color.nRed,color.nGreen,color.nBlue));
   oldpen = (HPEN)SelectObject(hdc,newpen);

   //先保存原來的點,畫出后NumOfPolygan組線時才擦畫
   for (i=0;i<NumOfPoint;i++) {
	  for (j=NumOfPolygan-1;j>0;j--) {
	     pt[i].Oldx[j]=pt[i].Oldx[j-1];
	     pt[i].Oldy[j]=pt[i].Oldy[j-1];
	  }
	  pt[i].Oldx[0]=pt[i].x;
	  pt[i].Oldy[0]=pt[i].y;
   }

   //是否跑到屏幕外,反彈
   for (i=0;i<NumOfPoint;i++) {
	  if (pt[i].x>=scrwth)
         { pt[i].vx=-rand()*vRange/RAND_MAX-1; ChangeColor(); }
	  else if (pt[i].x<=0)
         { pt[i].vx=rand()*vRange/RAND_MAX+1;  ChangeColor(); }

	  if (pt[i].y>=scrhgt)
         { pt[i].vy=-rand()*vRange/RAND_MAX-1; ChangeColor(); }
	  else if (pt[i].y<=0)
         { pt[i].vy=rand()*vRange/RAND_MAX+1;  ChangeColor(); }

      pt[i].x=pt[i].x+pt[i].vx;
      pt[i].y=pt[i].y+pt[i].vy;
   }

   //畫線
   MoveToEx(hdc,pt[0].x,pt[0].y,NULL);
   for (j=0;j<NumOfPoint-1;j++)
       LineTo(hdc,pt[j+1].x,pt[j+1].y);
   LineTo(hdc,pt[0].x,pt[0].y);

   Sleep(7);   //延遲0.007秒,控制速度!!!!

   //擦去前NumOfPolygan的那條線
   ReverseNewPen=CreatePen(PS_SOLID,1,RGB(0,0,0));
   SelectObject(hdc,ReverseNewPen);
   MoveToEx(hdc,pt[0].Oldx[NumOfPolygan-1],pt[0].Oldy[NumOfPolygan-1],NULL);
   for (j=0;j<NumOfPoint-1;j++)
	  LineTo(hdc,pt[j+1].Oldx[NumOfPolygan-1],pt[j+1].Oldy[NumOfPolygan-1]);
   LineTo(hdc,pt[0].Oldx[NumOfPolygan-1],pt[0].Oldy[NumOfPolygan-1]);

   SelectObject(hdc,oldpen);
   DeleteObject(newpen);
   DeleteObject(ReverseNewPen);
   ReleaseDC(hwnd,hdc);       //釋放窗口的設備環(huán)境

}

void TLines::ChangeColor()  //改變顏色
{
	if (rand()*10/RAND_MAX == 5) { //平均頂點撞擊墻壁10次改變一次顏色   
       color.nRed   = rand()*255/RAND_MAX;
       color.nGreen = rand()*255/RAND_MAX;
       color.nBlue  = rand()*255/RAND_MAX;
	}
}