/**************************************************************
*       Draw a real function F(x) by giving its equation      *
* ----------------------------------------------------------- *
* Ref.: Analyse numérique en C By Alain Reverchon and         *
*       Marc Ducamp, Armand Colin Editor, Paris, 1990".       *
*       (for files armath.h, fonction.cpp) [BIBLI 14].        *
* ----------------------------------------------------------- *
* SAMPLE RUN:                                                 *
*                                                             *
*                                                             *
*  Equation of Function f(x): "sin(x)/x"                      *
*                                                             *
*  Begin x: -16                                               *
*  End x  : 16                                                *
*  Number of points: 100                                      *
*                                                             *
*                                                             *
*  (A graph of the function f(x) is displayed).               *
*                                                             *
*                           C++ version by J-P Moreau, Paris. *
*                                  (www.jpmoreau.fr)          *
* ----------------------------------------------------------- *
* Note: this program demonstrates the capability of the module*
*       Fonction.cpp to compile a user defined real function  *
*       F(x), given by its equation, and to evaluate a current*
*       point.                                                *
*                                                             *
* Accepted signs and operators:                               *
* ----------------------------                                *
* 0,1,2,3,4,5,6,7,8,9,(,),-,+,*,/,^,SIN,COS,TAN,ARCSIN,ARCCOS,*
* ARCTAN,SH,CH,TH,ARGSH,ARGCH,ARGTH,ABS,INT,FRAC,FACT,EXP,LN, *
* SQR (^ for power, SQRT for square root).                    *
***************************************************************
uses functions ar_anal_fonction, ar_eval_f of fonction.cpp.  
     here no use is made of optional type ar_nombre.         
---------------------------------------------------------------
Used files: 
  grfunct1.mak,
  armath.h, fonction.cpp, graph2d.cpp, graph2d.h.
-------------------------------------------------------------*/
#include "armath.h"
#include <windows.h>

#define  REAL  double
#define  SQRT  sqrt

HDC  hdc;
RECT rect;
HPEN hpen, hpenOld;

//Functions used here of graph2D.cpp
void CourbeXY(int,int,float *,REAL,REAL);
void Legendes (int,char *,char *,char *,int,int,char *,int,int,char *);


//"home made" graphic commands for hdc environment used by above functions
void DrawPixel(int ix,int iy) {
  //sorry, no other available command found
  Rectangle(hdc,rect.left+ix,rect.top+iy,
	            rect.left+ix+2,rect.top+iy+1);
}

void Swap(int *i1,int *i2) {
  int it;
  it=*i1; *i1=*i2; *i2=it;
}

void DrawLine(int ix1,int iy1,int ix2,int iy2) {
  int i,il,ix,iy;
  REAL dx,dy;
  if (ix2<ix1) {
	Swap(&ix1,&ix2); Swap(&iy1,&iy2);
  }
  il=(int) SQRT((ix2-ix1)*(ix2-ix1)+(iy2-iy1)*(iy2-iy1));
  dx=(REAL) (ix2-ix1)/il; 
  dy=(REAL) (iy2-iy1)/il;
  ix=ix1; iy=iy1;
  for (i=1;i<il+1; i++) {
	DrawPixel(ix,iy);
	ix=(int) (ix1+i*dx); 
	iy=(int) (iy1+i*dy);
  }
}

void OutText(int ix,int iy,char *s) {
  RECT rct;
  rct.left=ix; rct.right=ix+10*strlen(s);
  rct.top=iy-5; rct.bottom=iy+15;
  DrawText(hdc, s, -1, &rct,
                DT_SINGLELINE | DT_CENTER | DT_VCENTER);
}



//calculate and draw discreet primitive of given function F(x)
void Exec_grfunct() {
  extern MaxX, MaxY;
  REAL  x1,x2;
  float Y[160];
  float dx,x;
  int i, ndata=160;
  char text[80];
  x1=-16; x2=16;
  //compile function f(x)
  strcpy(text,"sin(x)/x");
  ar_anal_fonction (text, (ar_fonction *) &ar_glob_f);
  //Evaluate ndata ordinates and put in table Y
  dx=(float) ((x2-x1)/(ndata-1));
  x=(float) x1 - dx;
  for (i=0; i<ndata; i++) {
    x += dx;
    Y[i]=(float) ar_eval_f(x);
  }
  //draw function F(x)
  MaxX=(rect.right-rect.left);   //drawing zone in pixels
  MaxY=(rect.bottom-rect.top);
  CourbeXY(ndata,10,Y,x1,x2);
  Legendes(10,"  SIN(X) / X ","X","Y",MaxX-220,50,"Curve: 160 points",
	                                       MaxX-220,80,"from x1=-16 to x2=16");
}

//Handle window Paint and Destroy messages
long FAR PASCAL /*_export*/ WndProc(HWND hwnd,
    UINT message, UINT wParam, LONG lParam) 
{
   
    PAINTSTRUCT ps;

    switch (message) {
        case WM_PAINT:
	    hdc = BeginPaint(hwnd, &ps);
	    GetClientRect(hwnd, &rect);
            hpen = CreatePen(PS_SOLID, 1, RGB(0, 0, 255));
            hpenOld = SelectObject(hdc,hpen);

            Exec_grfunct();
               
            SelectObject(hdc,hpenOld);
            DeleteObject(hpen);
            EndPaint(hwnd, &ps);
            return 0;
        case WM_DESTROY:
            PostQuitMessage(0);
            return 0;
    }
    return DefWindowProc(hwnd, message, wParam, lParam);
}

// main program
int PASCAL WinMain(HANDLE hInstance, HANDLE hPrevInstance,
    LPSTR lpszCmdParam, int nCmdShow)
{
    static char szAppName[] = "Grfunct";
    HWND        hwnd;
    MSG         msg;
    WNDCLASS    wndclass;

    if (!hPrevInstance) {
        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 = GetStockObject(WHITE_BRUSH);
        wndclass.lpszMenuName  = NULL;
        wndclass.lpszClassName = szAppName;

        RegisterClass(&wndclass);
    }

    hwnd = CreateWindow(szAppName,  // window class name
        " Drax a function defined by its equation",    // window caption
        WS_OVERLAPPEDWINDOW,        // window style                       
        CW_USEDEFAULT,              // initial x position
        CW_USEDEFAULT,              // initial y position
        CW_USEDEFAULT,              // initial x size
        CW_USEDEFAULT,              // initial y size
        NULL,                       // parent window handle
        NULL,                       // window menu handle
        hInstance,                  // program instance handle
        NULL);                      // creation parameters

   ShowWindow(hwnd, nCmdShow);
   UpdateWindow(hwnd);

   while (GetMessage(&msg, NULL, 0, 0)) {
       TranslateMessage(&msg);
       DispatchMessage(&msg);
   }
   return msg.wParam;
}

//end of file grfunct1.cpp