/* Filename:  Math3.cpp

   Programmers:  Brian LaSitis, Br. David Carlson, Br. Isidore Minerd

   Date:  March 5, 2003; August 15, 2009

   This Win32 program illustrates simple graphics by graphing a mathematical function, in
   this case a rational function.

   Although much of the Windows code in the program is not understandable to beginning
   students, the WM_PAINT section in the WndProc function is fairly easy to follow.
   Students who have a basic understanding of calling class functions can read this
   section of code and modify it to draw something of their choosing.

   Tested with:
      Microsoft Visual Studio 2005
      Microsoft Visual Studio 2008

   To compile this program in Visual C++ 6.0, create a new project of type "Win32 Application"
   (not Win32 Console application) and then make sure that "empty project" is selected.
   Do not select Console application.  You can then create a new C++ source file for this project
   and paste in this code.

   To compile this program in Visual C++ .NET, create a Visual C++ project of type "Win32 project"
   (not Console application) and under Application settings be sure that Windows application and
   Empty project are checked.  You can then create a new C++ file for this project and
   paste in this code.
*/

#include <windows.h>
#include <cmath>

// Global constant for pi:
const double pi = 3.1415926535;


// Function prototypes:

int g(int x);

LRESULT CALLBACK WndProc(HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam);


// For a Win32 app, there is a WinMain function, not a main function.  Ignore the gory Windows details.
INT WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPSTR szCmdLine, INT iCmdShow)
   {
   LPCWSTR szAppName = L"WinApp";
   LPCWSTR szWndName = L"Simple Drawing";

   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(WHITE_BRUSH);
   wndclass.lpszMenuName = NULL;
   wndclass.lpszClassName = szAppName;

   if (! RegisterClass(&wndclass))
      {
      MessageBox(NULL, L"Could not create window.", L"Error", 0);
      return 0;
      }

   hWnd = CreateWindow(szAppName, szWndName, WS_OVERLAPPEDWINDOW,
      CW_USEDEFAULT,   CW_USEDEFAULT, 800, 600, NULL, NULL, hInstance, NULL);

   ShowWindow(hWnd, iCmdShow);
   UpdateWindow(hWnd);

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

   return (int) msg.wParam;
   }


// This function processes the various messages for the window.
LRESULT CALLBACK WndProc(HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam)
   {
   int x;

   switch (message)
      {
      case WM_CREATE:
         return 0;

      case WM_PAINT:
         HDC hDC;
         PAINTSTRUCT ps;
         HPEN hOldPen, hNewPen;

         hDC = BeginPaint(hWnd, &ps);
         hNewPen = CreatePen(PS_SOLID, 1, RGB(0, 180, 180));   // aqua color (mixes green and blue)
         hOldPen = (HPEN)SelectObject(hDC, hNewPen);

         //*** Students: try changing the section between this comment line and the one marked below. ***

         // Print a message:
         TextOut(hDC, 50, 50, L"Graph", 5);

         // Draw the axes:
         MoveToEx(hDC, 100, 300, NULL);
         LineTo(hDC, 500, 300);
         MoveToEx(hDC, 300, 50, NULL);
         LineTo(hDC, 300, 550);

         // Draw the graph of the function g:
         for (x = -200; x <= 200; x++)
            SetPixel(hDC, 300 + x, 300 + g(x), RGB(0, 0, 255));   // blue color

         //*** Students: this is the end of the section that you might try to change. ***

         EndPaint(hWnd, &ps);
         return 0;

      case WM_DESTROY:
         PostQuitMessage(0);
         return 0;
      }

   return DefWindowProc(hWnd, message, wParam, lParam);
   }


/* Given:   x    An integer value.
   Task:    To compute the nearest integer to the value of g at x where g is a rational function.
   Return:  In the function name we return this integer approximation to the value of g at x.
*/
int g(int x)
   {
   return (50.0 * x - 1000.0) / (x + 20);
   }