/*========================================================================================

Name:   ARB_multisample.cpp
Author: Colt "MainRoach" McAnlis
Date:   4/29/04
Desc:   This file contains the context to load a WGL extension from a string
As well as collect the sample format available based upon the graphics card.

 ========================================================================================*/

#include <windows.h>
#include <gl/gl.h>
#include <gl/glu.h>

#include "ARB_Multisample.h"
#include "gamemain.h"

// Declairations We'll Use
#define WGL_SAMPLE_BUFFERS_ARB		 0x2041
#define WGL_SAMPLES_ARB			     0x2042

bool	arbMultisampleSupported	= false;
int		arbMultisampleFormat	= 0;

// WGLisExtensionSupported: This Is A Form Of The Extension For WGL
bool WGLisExtensionSupported(const char *extension)
{
  const size_t extlen = strlen(extension);
  const char *supported = NULL;
  
  // Try To Use wglGetExtensionStringARB On Current DC, If Possible
  PROC wglGetExtString = wglGetProcAddress("wglGetExtensionsStringARB");
  
  if (wglGetExtString)
    supported = ((char*(__stdcall*)(HDC))wglGetExtString)(wglGetCurrentDC());
  
  // If That Failed, Try Standard Opengl Extensions String
  if (supported == NULL)
    supported = (char*)glGetString(GL_EXTENSIONS);
  
  // If That Failed Too, Must Be No Extensions Supported
  if (supported == NULL)
    return false;
  
  // Begin Examination At Start Of String, Increment By 1 On False Match
  for (const char* p = supported; ; p++)
  {
    // Advance p Up To The Next Possible Match
    p = strstr(p, extension);
    
    if (p == NULL)
      return false;															// No Match
    
    // Make Sure That Match Is At The Start Of The String Or That
    // The Previous Char Is A Space, Or Else We Could Accidentally
    // Match "wglFunkywglExtension" With "wglExtension"
    
    // Also, Make Sure That The Following Character Is Space Or NULL
    // Or Else "wglExtensionTwo" Might Match "wglExtension"
    if ((p==supported || p[-1]==' ') && (p[extlen]=='\0' || p[extlen]==' '))
      return true;															// Match
  }
}

// InitMultisample: Used To Query The Multisample Frequencies
bool InitMultisample(HINSTANCE hInstance,HWND hWnd,PIXELFORMATDESCRIPTOR pfd)
{
  // See If The String Exists In WGL!
  if (!WGLisExtensionSupported("WGL_ARB_multisample"))
  {
    arbMultisampleSupported=false;
    return false;
  }
  
  // Get Our Pixel Format
  PFNWGLCHOOSEPIXELFORMATARBPROC wglChoosePixelFormatARB = (PFNWGLCHOOSEPIXELFORMATARBPROC)wglGetProcAddress("wglChoosePixelFormatARB");
  if (!wglChoosePixelFormatARB)
  {
    arbMultisampleSupported=false;
    return false;
  }
  
  // Get Our Current Device Context
  HDC hDC = GetDC(hWnd);
  
  int		pixelFormat;
  int		valid;
  UINT	numFormats;
  float	fAttributes[] = {0,0};
  
  // These Attributes Are The Bits We Want To Test For In Our Sample
  // Everything Is Pretty Standard, The Only One We Want To
  // Really Focus On Is The SAMPLE BUFFERS ARB And WGL SAMPLES
  // These Two Are Going To Do The Main Testing For Whether Or Not
  // We Support Multisampling On This Hardware.
  int iAttributes[] =
  {
    WGL_DRAW_TO_WINDOW_ARB,GL_TRUE,
    WGL_SUPPORT_OPENGL_ARB,GL_TRUE,
    WGL_ACCELERATION_ARB,WGL_FULL_ACCELERATION_ARB,
    WGL_COLOR_BITS_ARB,32,
    WGL_ALPHA_BITS_ARB,8,
    WGL_DEPTH_BITS_ARB,16,
    WGL_STENCIL_BITS_ARB,1,
    WGL_DOUBLE_BUFFER_ARB,GL_TRUE,
    WGL_SAMPLE_BUFFERS_ARB,GL_TRUE,
    WGL_SAMPLES_ARB, FGameOptions.FSamples,
    0,0
  };
  
  valid = wglChoosePixelFormatARB(hDC,iAttributes,fAttributes,1,&pixelFormat,&numFormats);
  
  // If We Returned True, And Our Format Count Is Greater Than 1
  if (valid && numFormats >= 1)
  {
    arbMultisampleSupported = true;
    arbMultisampleFormat = pixelFormat;
    return arbMultisampleSupported;
  }
  
  // Our Pixel Format With The Chosen Samples Failed, Test For 2 Samples
  iAttributes[19] = 0;
  valid = wglChoosePixelFormatARB(hDC,iAttributes,fAttributes,1,&pixelFormat,&numFormats);
  if (valid && numFormats >= 1)
  {
    arbMultisampleSupported = true;
    arbMultisampleFormat = pixelFormat;
    return arbMultisampleSupported;
  }
  
  // Return The Valid Format
  return  arbMultisampleSupported;
}