#include "sdl.h"
#include "GL_Functions.h"

int SDL_main(int argc, char* argv[])
{
	//Used in the main loop
	bool Done = false;

	//Used to store SDL events
	SDL_Event event;

	//Lets open the window and initialise opengl
	InitGL(1024,768);

	while(!Done)
	{
		//Clear the screen
		glClear(GL_COLOR_BUFFER_BIT);


		glBegin(GL_QUADS);

		glColor3f(1,0,0);
		glVertex2i(256, 128);

		glColor3f(0,1,0);
		glVertex2i(768, 128);

		glColor3f(0,0,1);
		glVertex2i(768, 640);

		glColor3f(1,1,1);
		glVertex2i(256, 640);

		glEnd();

		//Present that freshly drawn scene to the screen
		SDL_GL_SwapBuffers();


		//While we have events (keyboard, mouse, window etc)
		while( SDL_PollEvent(&event) )
		{
			// if the window X was clicked on, ALT_F4 etc
			if ( event.type == SDL_QUIT )
				Done = true;

			//If we have had a key press
			if ( event.type == SDL_KEYDOWN )
			{
				//And the key was escape
				if ( event.key.keysym.sym == SDLK_ESCAPE )
					Done = true;

			}

		}
	}

	SDL_Quit();

	return 0;
}

#ifndef _GL_FUNCTIONS_H_
#define _GL_FUNCTIONS_H_

//Includes for sdl, opengl, sdl_image
#include "sdl_opengl.h"
#include "sdl.h"
#include "sdl_image.h"

//Used to initialise SDL and OpenGL
int InitGL(int Width, int Height, bool fullscreen = false);

#endif

#include "GL_Functions.h"

int InitGL(int Width, int Height, bool fullscreen)
{
	int error;

	//Initialise SDL, with everything
	error = SDL_Init(SDL_INIT_EVERYTHING);

	//The following 6 lines setup the openGL settings
	//Setting up 32bit colour for the window
	//And to use Double buffering
	SDL_GL_SetAttribute(SDL_GL_DOUBLEBUFFER, 1);
	SDL_GL_SetAttribute(SDL_GL_DEPTH_SIZE, 32);
	SDL_GL_SetAttribute(SDL_GL_RED_SIZE, 8);
	SDL_GL_SetAttribute(SDL_GL_GREEN_SIZE, 8);
	SDL_GL_SetAttribute(SDL_GL_BLUE_SIZE, 8);
	SDL_GL_SetAttribute(SDL_GL_ALPHA_SIZE, 8);



	//This stores the information we want to initialise our display window with
	//We want OpenGL and a Hardware surface so it will use the graphics card acceleration
	//Binary OR is used to add all of the flags together
	unsigned int flags = SDL_OPENGL | SDL_HWSURFACE | (fullscreen ? SDL_FULLSCREEN : 0);

	//Set the Video mode, with the correct Width, Height, bitdepth (32bit) to match our
	//OpenGL attributes we setup above.
	SDL_SetVideoMode(Width, Height, 32, flags);


	//Set the Clear Colour, this is the colour the window is cleared to as black
	glClearColor(0.0, 0.0, 0.0, 0.0);

	//Set the draw colour, to white.
	glColor4f( 1,1,1,1);

	//This is to setup an Ortho graphic projection. An ortho graphic projection has no perspective
	//It setups the projection so its Width and height matches the screen.
	//So 1 unit in world coordinates is 1 pixel on the screen.
	glMatrixMode(GL_PROJECTION);	
	glLoadIdentity();
	glOrtho(0.0, Width, Height, 0.0, 0.0, 10.0);

	//Enable 2 dimensional textures
	glEnable(GL_TEXTURE_2D);


	//Enable blending (transparencies) and setup the blend function correctly.
	glEnable(GL_BLEND);
	glBlendFunc( GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA );

	//This complex horrid mess disables V-Sync.
	typedef void (APIENTRY * WGLSWAPINTERVALEXT) (int);
	WGLSWAPINTERVALEXT wglSwapIntervalEXT = (WGLSWAPINTERVALEXT) 
		wglGetProcAddress("wglSwapIntervalEXT");
	if (wglSwapIntervalEXT) {
		wglSwapIntervalEXT(0); // disable vertical synchronisation
	}

	return error;
}