//This is a drawing program

void DrawIt()
{
  ClearWindowText;
}

void Doodle()
{
  I8 cmd,x1,y1,x2,y2,p1,p2,color=GR_BLACK;
  U4 old_update_window=Fs->update_window;
  U4 old_ip_double=Bts(&Fs->crt_flags,CRTf_NO_DOUBLE_CLICK);
  U4 old_inhibit=ip_inhibit_win_operations;
  GrBitMap *base=GrNew(grbase);
  base->color=ROP_XOR+(color ^ GR_WHITE);
  ip_inhibit_win_operations=TRUE;
  MaximizeWindow;
  Fs->update_window=&DrawIt;
  GrClear;
  PutS("$$CL$$");
  while (TRUE) {
    cmd=GetMsg(&p1,&p2,
      (1<<MSG_KEY_DOWN)+(1<<MSG_IP_L_DOWN)+
      (1<<MSG_IP_R_UP));
    if (cmd==MSG_KEY_DOWN) {
      Fs->update_window=old_update_window;
      GrClear;
      AssignBit(&Fs->crt_flags,CRTf_NO_DOUBLE_CLICK,old_ip_double);
      ip_inhibit_win_operations=old_inhibit;
      GrDel(base);
      return;
    } else if (cmd==MSG_IP_R_UP) {
      ip_inhibit_win_operations=FALSE;
      color=PopUpColor;
      base->color=ROP_XOR+(color ^ GR_WHITE);
      ip_inhibit_win_operations=TRUE;
    } else {
      x1=p1; y1=p2;
      x2=p1; y2=p2;
      while (cmd!=MSG_IP_L_UP) {
	GrLine3(base,x1,y1,0,x2,y2,0);
	cmd=GetMsg(&p1,&p2,
  	  (1<<MSG_IP_L_UP)+(1<<MSG_IP_MOVE));
	GrLine3(base,x1,y1,0,x2,y2,0);
	x2=p1; y2=p2;
      }
      GrLine3(base,x1,y1,0,x2,y2,0);
    }
  }
}

Doodle;  //Execute when #included
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