// DEMO4_4.CPP  - Ellipse Animation Demo

// INCLUDES ///////////////////////////////////////////////
#define WIN32_LEAN_AND_MEAN  // just say no to MFC

#include <windows.h>   // include all the windows headers
#include <windowsx.h>  // include useful macros
#include <mmsystem.h>  // very important and include WINMM.LIB too!
#include <stdio.h>
#include <stdlib.h>
#include <math.h>

// DEFINES ////////////////////////////////////////////////

// defines for windows 
#define WINDOW_CLASS_NAME "WINCLASS1"

#define WINDOW_WIDTH  400
#define WINDOW_HEIGHT 300

// MACROS /////////////////////////////////////////////////

#define KEYDOWN(vk_code) ((GetAsyncKeyState(vk_code) & 0x8000) ? 1 : 0)
#define KEYUP(vk_code)   ((GetAsyncKeyState(vk_code) & 0x8000) ? 0 : 1)

// GLOBALS ////////////////////////////////////////////////
HWND      main_window_handle = NULL; // globally track main window

HINSTANCE hinstance_app      = NULL; // globally track hinstance
char buffer[80];                     // general printing buffer

// FUNCTIONS //////////////////////////////////////////////
LRESULT CALLBACK WindowProc(HWND hwnd, 
						    UINT msg, 
                            WPARAM wparam, 
                            LPARAM lparam)
{
// this is the main message handler of the system
PAINTSTRUCT		ps;		// used in WM_PAINT
HDC				hdc;	// handle to a device context
char buffer[80];        // used to print strings

// what is the message 
switch(msg)
	{	
	case WM_CREATE: 
        {
		// do initialization stuff here
        // return success
		return(0);
		} break;
   
	case WM_PAINT: 
		{
		// simply validate the window 
   	    hdc = BeginPaint(hwnd,&ps);	 
        
        // end painting
        EndPaint(hwnd,&ps);

        // return success
		return(0);
   		} break;

	case WM_DESTROY: 
		{

		// kill the application, this sends a WM_QUIT message 
		PostQuitMessage(0);

        // return success
		return(0);
		} break;

	default:break;

    } // end switch

// process any messages that we didn't take care of 
return (DefWindowProc(hwnd, msg, wparam, lparam));

} // end WinProc

// WINMAIN ////////////////////////////////////////////////
int WINAPI WinMain(	HINSTANCE hinstance,
					HINSTANCE hprevinstance,
					LPSTR lpcmdline,
					int ncmdshow)
{

WNDCLASSEX winclass; // this will hold the class we create
HWND	   hwnd;	 // generic window handle
MSG		   msg;		 // generic message
HDC        hdc;      // graphics device context

// first fill in the window class stucture
winclass.cbSize         = sizeof(WNDCLASSEX);
winclass.style			= CS_DBLCLKS | CS_OWNDC | 
                          CS_HREDRAW | CS_VREDRAW;
winclass.lpfnWndProc	= WindowProc;
winclass.cbClsExtra		= 0;
winclass.cbWndExtra		= 0;
winclass.hInstance		= hinstance;
winclass.hIcon			= LoadIcon(NULL, IDI_APPLICATION);
winclass.hCursor		= LoadCursor(NULL, IDC_ARROW); 
winclass.hbrBackground	= (HBRUSH)GetStockObject(BLACK_BRUSH);
winclass.lpszMenuName	= NULL;
winclass.lpszClassName	= WINDOW_CLASS_NAME;
winclass.hIconSm        = LoadIcon(NULL, IDI_APPLICATION);

// save hinstance in global
hinstance_app = hinstance;

// register the window class
if (!RegisterClassEx(&winclass))
	return(0);

// create the window
if (!(hwnd = CreateWindowEx(NULL,                // extended style
                            WINDOW_CLASS_NAME,   // class
						    "Ellipse Animation Demo", // title
						    WS_OVERLAPPEDWINDOW | WS_VISIBLE,
					 	    0,0,	  // initial x,y
						    WINDOW_WIDTH, // initial width
                            WINDOW_HEIGHT,// initial height
						    NULL,	  // handle to parent 
						    NULL,	  // handle to menu
						    hinstance,// instance of this application
						    NULL)))	// extra creation parms
return(0);

// save main window handle
main_window_handle = hwnd;

// get the graphics device context once this time and keep it
// this is possible due to the CS_OWNDC flag
hdc = GetDC(hwnd);

// seed random number generator
srand(GetTickCount());

// create the pens and brushes
HPEN   white_pen = CreatePen(PS_SOLID, 1, RGB(255,255,255));
HPEN   black_pen = CreatePen(PS_SOLID, 1, RGB(0,0,0));
HBRUSH green_brush = CreateSolidBrush(RGB(0,255,0));
HBRUSH black_brush = CreateSolidBrush(RGB(0,0,0));

// starting position of ball
int ball_x = WINDOW_WIDTH/2;
int ball_y = WINDOW_HEIGHT/2;

// initial velocity of ball
int xv = -4+rand()%8;
int yv = -4+rand()%8;

// enter main event loop, but this time we use PeekMessage()
// instead of GetMessage() to retrieve messages
while(TRUE)
	{
    // test if there is a message in queue, if so get it
	if (PeekMessage(&msg,NULL,0,0,PM_REMOVE))
	   { 
	   // test if this is a quit
       if (msg.message == WM_QUIT)
           break;
	
	   // translate any accelerator keys
	   TranslateMessage(&msg);

	   // send the message to the window proc
	   DispatchMessage(&msg);
	   } // end if


    // ERASE the last position of the ball
    
    // first select the black pen and brush into context
    SelectObject(hdc, black_pen);
    SelectObject(hdc, black_brush);

    // draw the ball
    Ellipse(hdc, ball_x, ball_y, ball_x + 32, ball_y + 32);
    
    // MOVE the ball
    ball_x+=xv;
    ball_y+=yv;

    // test for collisions, first x-axis
    if (ball_x < 0 || ball_x > WINDOW_WIDTH - 32)
       { 
       // invert x-velocity of ball
       xv=-xv;

       // push ball back
       ball_x+=xv;

       } // end if
    else
    // test for y-axis collisions
    if (ball_y < 0 || ball_y > WINDOW_HEIGHT - 32)
       { 
       // invert y-velocity of ball
       yv=-yv;

       // push ball back
       ball_y+=yv;

       } // end if

    // now select the green and white colors for brush and pen
    SelectObject(hdc, white_pen);
    SelectObject(hdc, green_brush);

    // DRAW the ball
    Ellipse(hdc, ball_x, ball_y, ball_x + 32, ball_y + 32);

    // main game processing goes here
    if (KEYDOWN(VK_ESCAPE))
       SendMessage(hwnd, WM_CLOSE, 0,0);

    // slow system down a little
    Sleep(10); 
       
	} // end while

// delete all the objects
DeleteObject(white_pen);
DeleteObject(black_pen);
DeleteObject(green_brush);
DeleteObject(black_brush);

// release the device context
ReleaseDC(hwnd,hdc);

// return to Windows like this
return(msg.wParam);

} // end WinMain

///////////////////////////////////////////////////////////