AGG && SDL_Lock_texture

#include "SDL.h"
#include "agg_renderer_base.h"
#include "agg_pixfmt_rgba.h"
#include "agg_scanline_u.h"
#include "agg_rasterizer_scanline_aa.h"
#include "agg_renderer_scanline.h"
#include "agg_path_storage.h"

enum
{
    frame_width = 800,
    frame_height = 600
};

int main(int argc, char * argv[])
{
    //initialize SDL
    //--------------
    atexit(SDL_Quit);
    SDL_Init(SDL_INIT_VIDEO);
    SDL_Window* win = SDL_CreateWindow
    (
        "SDL&AGG",
        SDL_WINDOWPOS_CENTERED,
        SDL_WINDOWPOS_CENTERED,
        frame_width,
        frame_height,
        0
    );
    SDL_Renderer* ren = SDL_CreateRenderer
    (
        win,
        -1,
        0
    );

    //initialize AGG with memory allocated by SDL
    Uint32 rmask, gmask, bmask, amask;

    #if SDL_BYTEORDER == SDL_BIG_ENDIAN
    rmask = 0xff000000;
    gmask = 0x00ff0000;
    bmask = 0x0000ff00;
    amask = 0x000000ff;
    #else
    rmask = 0x000000ff;
    gmask = 0x0000ff00;
    bmask = 0x00ff0000;
    amask = 0xff000000;
    #endif

    SDL_Surface* surf = SDL_CreateRGBSurface
    (
        0,
        frame_width,
        frame_height,
        32,
        rmask,
        gmask,
        bmask,
        amask
    );

    SDL_LockSurface(surf);

    agg::rendering_buffer rbuf //rendering buffer object
    (
        (unsigned char*)surf->pixels,
        frame_width,
        frame_height,
        frame_width * 4
    );

    agg::pixfmt_rgba32 pixf(rbuf);
    agg::renderer_base<agg::pixfmt_rgba32> rbase(pixf);
        //clear surf->pixels
    rbase.clear(agg::rgba8(0, 0, 255, 255));

    agg::scanline_u8 scanline;
    agg::rasterizer_scanline_aa<> ras;

    agg::renderer_scanline_aa_solid
    <
        agg::renderer_base
        <
            agg::pixfmt_rgba32
        >
    > rscan(rbase);

    //create agg paths
    agg::path_storage path;
    path.move_to(10, 10);
    path.line_to(frame_width-10, frame_height-10);
    path.line_to(frame_width-10, 10);
    path.line_to(10, frame_height-10);

    ras.add_path(path);
    rscan.color(agg::rgba8(0, 255, 0, 255));

    //draw paths to surf->pixels
    agg::render_scanlines(ras, scanline, rscan);

    SDL_UnlockSurface(surf); //finished drawing

    //convert pixel format and display image

    SDL_PixelFormat* sdl_pixfmt = new SDL_PixelFormat;
    sdl_pixfmt->format = SDL_GetWindowPixelFormat(win);

    SDL_Surface* conv_surf = SDL_ConvertSurface
    (
        surf,
        sdl_pixfmt,
        0
    );

    SDL_Surface* surf_to_tex = SDL_CreateRGBSurface
    (
        0,
        frame_width,
        frame_height,
        32,
        rmask,
        gmask,
        bmask,
        amask
    );

    SDL_Texture* tex = SDL_CreateTexture
    (
        ren,
        SDL_PIXELFORMAT_RGBA8888,
        SDL_TEXTUREACCESS_STREAMING,
        frame_width,
        frame_height
    );

    SDL_LockTexture
    (
        tex,
        NULL,
        &surf_to_tex->pixels,
        &surf_to_tex->pitch
    );

    SDL_BlitSurface
    (
        conv_surf,
        NULL,
        surf_to_tex,
        NULL
    );


    SDL_UnlockTexture(tex);

    SDL_RenderCopy
    (
        ren,
        tex,
        NULL,
        NULL
    );
    SDL_RenderPresent(ren);
/*
    SDL_Texture* tex2 = SDL_CreateTextureFromSurface(ren, surf);
    SDL_RenderCopy
    (
        ren,
        tex2,
        NULL,
        NULL
    );
    SDL_RenderPresent(ren);
*/
    //main event loop
    //---------------
    SDL_Event e;

    while(1) //loop until user quits
    {
        if(SDL_PollEvent(&e))
        {
            switch(e.type)
            {
                case SDL_QUIT:
                    return 0;

                case SDL_KEYDOWN:
                    if(e.key.keysym.sym == SDLK_ESCAPE)
                        return(0);
            }
        }
        SDL_Delay(1); //speedbump, share the processor
    }

    return 0;
}