/*
    SDL - Simple DirectMedia Layer
    Copyright (C) 1997-2009 Sam Lantinga

    This library is free software; you can redistribute it and/or
    modify it under the terms of the GNU Lesser General Public
    License as published by the Free Software Foundation; either
    version 2.1 of the License, or (at your option) any later version.

    This library is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
    Lesser General Public License for more details.

    You should have received a copy of the GNU Lesser General Public
    License along with this library; if not, write to the Free Software
    Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA

    Sam Lantinga
    slouken@libsdl.org
*/
#include "SDL_config.h"

#if SDL_VIDEO_RENDER_OGL_ES

#include "SDL_video.h"
#include "SDL_opengles.h"
#include "SDL_sysvideo.h"
#include "SDL_pixels_c.h"
#include "SDL_rect_c.h"
#include "SDL_yuv_sw_c.h"

/* OpenGL ES 1.1 renderer implementation, based on the OpenGL renderer */

static const float inv255f = 1.0f / 255.0f;

static SDL_Renderer *GLES_CreateRenderer(SDL_Window * window, Uint32 flags);
static int GLES_ActivateRenderer(SDL_Renderer * renderer);
static int GLES_DisplayModeChanged(SDL_Renderer * renderer);
static int GLES_CreateTexture(SDL_Renderer * renderer, SDL_Texture * texture);
static int GLES_QueryTexturePixels(SDL_Renderer * renderer,
                                   SDL_Texture * texture, void **pixels,
                                   int *pitch);
static int GLES_SetTexturePalette(SDL_Renderer * renderer,
                                  SDL_Texture * texture,
                                  const SDL_Color * colors, int firstcolor,
                                  int ncolors);
static int GLES_GetTexturePalette(SDL_Renderer * renderer,
                                  SDL_Texture * texture, SDL_Color * colors,
                                  int firstcolor, int ncolors);
static int GLES_SetTextureColorMod(SDL_Renderer * renderer,
                                   SDL_Texture * texture);
static int GLES_SetTextureAlphaMod(SDL_Renderer * renderer,
                                   SDL_Texture * texture);
static int GLES_SetTextureBlendMode(SDL_Renderer * renderer,
                                    SDL_Texture * texture);
static int GLES_SetTextureScaleMode(SDL_Renderer * renderer,
                                    SDL_Texture * texture);
static int GLES_UpdateTexture(SDL_Renderer * renderer, SDL_Texture * texture,
                              const SDL_Rect * rect, const void *pixels,
                              int pitch);
static int GLES_LockTexture(SDL_Renderer * renderer, SDL_Texture * texture,
                            const SDL_Rect * rect, int markDirty,
                            void **pixels, int *pitch);
static void GLES_UnlockTexture(SDL_Renderer * renderer,
                               SDL_Texture * texture);
static void GLES_DirtyTexture(SDL_Renderer * renderer, SDL_Texture * texture,
                              int numrects, const SDL_Rect * rects);
static int GLES_RenderFill(SDL_Renderer * renderer, Uint8 r, Uint8 g, Uint8 b,
                           Uint8 a, const SDL_Rect * rect);
static int GLES_RenderCopy(SDL_Renderer * renderer, SDL_Texture * texture,
                           const SDL_Rect * srcrect,
                           const SDL_Rect * dstrect);
static void GLES_RenderPresent(SDL_Renderer * renderer);
static void GLES_DestroyTexture(SDL_Renderer * renderer,
                                SDL_Texture * texture);
static void GLES_DestroyRenderer(SDL_Renderer * renderer);


SDL_RenderDriver GL_ES_RenderDriver = {
    GLES_CreateRenderer,
    {
     "opengl_es",
     (SDL_RENDERER_SINGLEBUFFER | SDL_RENDERER_PRESENTDISCARD |
      SDL_RENDERER_PRESENTVSYNC | SDL_RENDERER_ACCELERATED),
     (SDL_TEXTUREMODULATE_NONE | SDL_TEXTUREMODULATE_COLOR |
      SDL_TEXTUREMODULATE_ALPHA),
     (SDL_TEXTUREBLENDMODE_NONE | SDL_TEXTUREBLENDMODE_MASK |
      SDL_TEXTUREBLENDMODE_BLEND | SDL_TEXTUREBLENDMODE_ADD |
      SDL_TEXTUREBLENDMODE_MOD),
     (SDL_TEXTURESCALEMODE_NONE | SDL_TEXTURESCALEMODE_FAST |
      SDL_TEXTURESCALEMODE_SLOW), 2,
     {
      SDL_PIXELFORMAT_RGB24,
      SDL_PIXELFORMAT_ABGR8888,
      },
     0,
     0}
};

typedef struct
{
    SDL_GLContext context;
    SDL_bool updateSize;
    int blendMode;

#ifndef APIENTRY
#define APIENTRY
#endif

    SDL_bool useDrawTexture;
    SDL_bool GL_OES_draw_texture_supported;

    /* OpenGL ES functions */
#define SDL_PROC(ret,func,params) ret (APIENTRY *func) params;
#include "SDL_glesfuncs.h"
#undef SDL_PROC

} GLES_RenderData;

typedef struct
{
    GLuint texture;
    GLenum type;
    GLfloat texw;
    GLfloat texh;
    GLenum format;
    GLenum formattype;
    void *pixels;
    int pitch;
    SDL_DirtyRectList dirty;
} GLES_TextureData;

static void
GLES_SetError(const char *prefix, GLenum result)
{
    const char *error;

    switch (result) {
    case GL_NO_ERROR:
        error = "GL_NO_ERROR";
        break;
    case GL_INVALID_ENUM:
        error = "GL_INVALID_ENUM";
        break;
    case GL_INVALID_VALUE:
        error = "GL_INVALID_VALUE";
        break;
    case GL_INVALID_OPERATION:
        error = "GL_INVALID_OPERATION";
        break;
    case GL_STACK_OVERFLOW:
        error = "GL_STACK_OVERFLOW";
        break;
    case GL_STACK_UNDERFLOW:
        error = "GL_STACK_UNDERFLOW";
        break;
    case GL_OUT_OF_MEMORY:
        error = "GL_OUT_OF_MEMORY";
        break;
    default:
        error = "UNKNOWN";
        break;
    }
    SDL_SetError("%s: %s", prefix, error);
}

static int
GLES_LoadFunctions(GLES_RenderData * data)
{

#define SDL_PROC(ret,func,params) \
	data->func = func;
#include "SDL_glesfuncs.h"
#undef SDL_PROC

    return 0;
}

void
GLES_AddRenderDriver(_THIS)
{
    if (_this->GL_CreateContext) {
        SDL_AddRenderDriver(0, &GL_ES_RenderDriver);
    }
}

SDL_Renderer *
GLES_CreateRenderer(SDL_Window * window, Uint32 flags)
{

    SDL_Renderer *renderer;
    GLES_RenderData *data;
    GLint value;
    int doublebuffer;

    if (!(window->flags & SDL_WINDOW_OPENGL)) {
        if (SDL_RecreateWindow(window, window->flags | SDL_WINDOW_OPENGL) < 0) {
            return NULL;
        }
    }

    renderer = (SDL_Renderer *) SDL_calloc(1, sizeof(*renderer));
    if (!renderer) {
        SDL_OutOfMemory();
        return NULL;
    }

    data = (GLES_RenderData *) SDL_calloc(1, sizeof(*data));
    if (!data) {
        GLES_DestroyRenderer(renderer);
        SDL_OutOfMemory();
        return NULL;
    }

    renderer->ActivateRenderer = GLES_ActivateRenderer;
    renderer->DisplayModeChanged = GLES_DisplayModeChanged;
    renderer->CreateTexture = GLES_CreateTexture;
    renderer->QueryTexturePixels = GLES_QueryTexturePixels;
    renderer->SetTexturePalette = GLES_SetTexturePalette;
    renderer->GetTexturePalette = GLES_GetTexturePalette;
    renderer->SetTextureColorMod = GLES_SetTextureColorMod;
    renderer->SetTextureAlphaMod = GLES_SetTextureAlphaMod;
    renderer->SetTextureBlendMode = GLES_SetTextureBlendMode;
    renderer->SetTextureScaleMode = GLES_SetTextureScaleMode;
    renderer->UpdateTexture = GLES_UpdateTexture;
    renderer->LockTexture = GLES_LockTexture;
    renderer->UnlockTexture = GLES_UnlockTexture;
    renderer->DirtyTexture = GLES_DirtyTexture;
    renderer->RenderFill = GLES_RenderFill;
    renderer->RenderCopy = GLES_RenderCopy;
    renderer->RenderPresent = GLES_RenderPresent;
    renderer->DestroyTexture = GLES_DestroyTexture;
    renderer->DestroyRenderer = GLES_DestroyRenderer;
    renderer->info = GL_ES_RenderDriver.info;
    renderer->window = window->id;
    renderer->driverdata = data;


    renderer->info.flags =
        (SDL_RENDERER_PRESENTDISCARD | SDL_RENDERER_ACCELERATED);

    if (GLES_LoadFunctions(data) < 0) {
        GLES_DestroyRenderer(renderer);
        return NULL;
    }

    data->context = SDL_GL_CreateContext(window->id);
    if (!data->context) {
        GLES_DestroyRenderer(renderer);
        return NULL;
    }
    if (SDL_GL_MakeCurrent(window->id, data->context) < 0) {
        GLES_DestroyRenderer(renderer);
        return NULL;
    }

    if (flags & SDL_RENDERER_PRESENTVSYNC) {
        SDL_GL_SetSwapInterval(1);
    } else {
        SDL_GL_SetSwapInterval(0);
    }
    if (SDL_GL_GetSwapInterval() > 0) {
        renderer->info.flags |= SDL_RENDERER_PRESENTVSYNC;
    }

    if (SDL_GL_GetAttribute(SDL_GL_DOUBLEBUFFER, &doublebuffer) == 0) {
        if (!doublebuffer) {
            renderer->info.flags |= SDL_RENDERER_SINGLEBUFFER;
        }
    }

    if (SDL_GL_ExtensionSupported("GL_OES_draw_texture")) {
        data->GL_OES_draw_texture_supported = SDL_TRUE;
        data->useDrawTexture = SDL_TRUE;
    } else {
        data->GL_OES_draw_texture_supported = SDL_FALSE;
        data->useDrawTexture = SDL_FALSE;
    }

    data->glGetIntegerv(GL_MAX_TEXTURE_SIZE, &value);
    renderer->info.max_texture_width = value;
    data->glGetIntegerv(GL_MAX_TEXTURE_SIZE, &value);
    renderer->info.max_texture_height = value;

    /* Set up parameters for rendering */
    data->blendMode = -1;
    data->glDisable(GL_DEPTH_TEST);
    data->glDisable(GL_CULL_FACE);
    data->glEnable(GL_TEXTURE_2D);
    data->updateSize = SDL_TRUE;

    return renderer;
}

static int
GLES_ActivateRenderer(SDL_Renderer * renderer)
{

    GLES_RenderData *data = (GLES_RenderData *) renderer->driverdata;
    SDL_Window *window = SDL_GetWindowFromID(renderer->window);

    if (SDL_GL_MakeCurrent(window->id, data->context) < 0) {
        return -1;
    }
    if (data->updateSize) {
        data->glMatrixMode(GL_PROJECTION);
        data->glLoadIdentity();
        data->glMatrixMode(GL_MODELVIEW);
        data->glLoadIdentity();
        data->glViewport(0, 0, window->w, window->h);
        data->glOrthof(0.0, (GLfloat) window->w, (GLfloat) window->h, 0.0,
                       0.0, 1.0);
        data->updateSize = SDL_FALSE;
    }
    return 0;
}

static int
GLES_DisplayModeChanged(SDL_Renderer * renderer)
{
    GLES_RenderData *data = (GLES_RenderData *) renderer->driverdata;

    data->updateSize = SDL_TRUE;
    return 0;
}

static __inline__ int
power_of_2(int input)
{
    int value = 1;

    while (value < input) {
        value <<= 1;
    }
    return value;
}

static int
GLES_CreateTexture(SDL_Renderer * renderer, SDL_Texture * texture)
{
    GLES_RenderData *renderdata = (GLES_RenderData *) renderer->driverdata;
    SDL_Window *window = SDL_GetWindowFromID(renderer->window);
    GLES_TextureData *data;
    GLint internalFormat;
    GLenum format, type;
    int texture_w, texture_h;
    GLenum result;
    switch (texture->format) {
    case SDL_PIXELFORMAT_INDEX1LSB:
    case SDL_PIXELFORMAT_INDEX1MSB:
    case SDL_PIXELFORMAT_INDEX8:
    case SDL_PIXELFORMAT_RGB332:
    case SDL_PIXELFORMAT_RGB444:
    case SDL_PIXELFORMAT_RGB555:
    case SDL_PIXELFORMAT_ARGB4444:
    case SDL_PIXELFORMAT_ARGB1555:
    case SDL_PIXELFORMAT_BGR24:
    case SDL_PIXELFORMAT_BGR888:
    case SDL_PIXELFORMAT_RGB888:
    case SDL_PIXELFORMAT_RGBA8888:
    case SDL_PIXELFORMAT_ARGB2101010:
    case SDL_PIXELFORMAT_ARGB8888:
    case SDL_PIXELFORMAT_RGB24:
        internalFormat = GL_RGB;
        format = GL_RGB;
        type = GL_UNSIGNED_BYTE;
        break;
    case SDL_PIXELFORMAT_ABGR8888:
        internalFormat = GL_RGBA;
        format = GL_RGBA;
        type = GL_UNSIGNED_BYTE;
        break;
        /*
           These formats would be supported if SDL had the necessary pixel formats
           case SDL_PIXELFORMAT_BGR565:
           internalFormat = GL_RGB;
           format = GL_RGB;
           type = GL_UNSIGNED_SHORT_5_6_5;
           break;                       
           case SDL_PIXELFORMAT_ABGR5551:
           internalFormat = GL_RGBA;
           format = GL_RGBA;
           type = GL_UNSIGNED_SHORT_5_5_5_1;
           break;
           case SDL_PIXELFORMAT_ABGR4444:
           internalFormat = GL_RGBA;
           format = GL_RGBA;
           type = GL_UNSIGNED_SHORT_4_4_4_4;
           break;
         */
    default:
        SDL_SetError("Unsupported texture format");
        return -1;
    }

    data = (GLES_TextureData *) SDL_calloc(1, sizeof(*data));
    if (!data) {
        SDL_OutOfMemory();
        return -1;
    }

    if (texture->access == SDL_TEXTUREACCESS_STREAMING) {
        data->pitch = texture->w * SDL_BYTESPERPIXEL(texture->format);
        data->pixels = SDL_malloc(texture->h * data->pitch);
        if (!data->pixels) {
            SDL_OutOfMemory();
            SDL_free(data);
            return -1;
        }
    }

    texture->driverdata = data;

    renderdata->glGetError();
    renderdata->glGenTextures(1, &data->texture);

    data->type = GL_TEXTURE_2D;
    /* no NPOV textures allowed in OpenGL ES (yet) */
    texture_w = power_of_2(texture->w);
    texture_h = power_of_2(texture->h);
    data->texw = (GLfloat) texture->w / texture_w;
    data->texh = (GLfloat) texture->h / texture_h;

    data->format = format;
    data->formattype = type;
    renderdata->glBindTexture(data->type, data->texture);
    renderdata->glTexParameteri(data->type, GL_TEXTURE_MIN_FILTER,
                                GL_NEAREST);
    renderdata->glTexParameteri(data->type, GL_TEXTURE_MAG_FILTER,
                                GL_NEAREST);
    renderdata->glTexParameteri(data->type, GL_TEXTURE_WRAP_S,
                                GL_CLAMP_TO_EDGE);
    renderdata->glTexParameteri(data->type, GL_TEXTURE_WRAP_T,
                                GL_CLAMP_TO_EDGE);

    renderdata->glTexImage2D(data->type, 0, internalFormat, texture_w,
                             texture_h, 0, format, type, NULL);

    result = renderdata->glGetError();
    if (result != GL_NO_ERROR) {
        GLES_SetError("glTexImage2D()", result);
        return -1;
    }
    return 0;
}

static int
GLES_QueryTexturePixels(SDL_Renderer * renderer, SDL_Texture * texture,
                        void **pixels, int *pitch)
{
    GLES_TextureData *data = (GLES_TextureData *) texture->driverdata;

    *pixels = data->pixels;
    *pitch = data->pitch;
    return 0;
}

static int
GLES_SetTexturePalette(SDL_Renderer * renderer, SDL_Texture * texture,
                       const SDL_Color * colors, int firstcolor, int ncolors)
{
    SDL_SetError("OpenGL ES does not support paletted textures");
    return -1;
}

static int
GLES_GetTexturePalette(SDL_Renderer * renderer, SDL_Texture * texture,
                       SDL_Color * colors, int firstcolor, int ncolors)
{
    SDL_SetError("OpenGL ES does not support paletted textures");
    return -1;
}

static void
SetupTextureUpdate(GLES_RenderData * renderdata, SDL_Texture * texture,
                   int pitch)
{


    GLES_TextureData *data = (GLES_TextureData *) texture->driverdata;
    renderdata->glBindTexture(data->type, data->texture);
    renderdata->glPixelStorei(GL_UNPACK_ALIGNMENT, 1);
}

static int
GLES_SetTextureColorMod(SDL_Renderer * renderer, SDL_Texture * texture)
{
    return 0;
}

static int
GLES_SetTextureAlphaMod(SDL_Renderer * renderer, SDL_Texture * texture)
{
    return 0;
}

static int
GLES_SetTextureBlendMode(SDL_Renderer * renderer, SDL_Texture * texture)
{
    switch (texture->blendMode) {
    case SDL_TEXTUREBLENDMODE_NONE:
    case SDL_TEXTUREBLENDMODE_MASK:
    case SDL_TEXTUREBLENDMODE_BLEND:
    case SDL_TEXTUREBLENDMODE_ADD:
    case SDL_TEXTUREBLENDMODE_MOD:
        return 0;
    default:
        SDL_Unsupported();
        texture->blendMode = SDL_TEXTUREBLENDMODE_NONE;
        return -1;
    }
}

static int
GLES_SetTextureScaleMode(SDL_Renderer * renderer, SDL_Texture * texture)
{
    switch (texture->scaleMode) {
    case SDL_TEXTURESCALEMODE_NONE:
    case SDL_TEXTURESCALEMODE_FAST:
    case SDL_TEXTURESCALEMODE_SLOW:
        return 0;
    case SDL_TEXTURESCALEMODE_BEST:
        SDL_Unsupported();
        texture->scaleMode = SDL_TEXTURESCALEMODE_SLOW;
        return -1;
    default:
        SDL_Unsupported();
        texture->scaleMode = SDL_TEXTURESCALEMODE_NONE;
        return -1;
    }
}

static int
GLES_UpdateTexture(SDL_Renderer * renderer, SDL_Texture * texture,
                   const SDL_Rect * rect, const void *pixels, int pitch)
{
    GLES_RenderData *renderdata = (GLES_RenderData *) renderer->driverdata;
    GLES_TextureData *data = (GLES_TextureData *) texture->driverdata;
    GLenum result;

    SetupTextureUpdate(renderdata, texture, pitch);
    renderdata->glGetError();
    renderdata->glTexSubImage2D(data->type, 0, rect->x, rect->y, rect->w,
                                rect->h, data->format, data->formattype,
                                pixels);
    result = renderdata->glGetError();
    if (result != GL_NO_ERROR) {
        GLES_SetError("glTexSubImage2D()", result);
        return -1;
    }
    return 0;
}

static int
GLES_LockTexture(SDL_Renderer * renderer, SDL_Texture * texture,
                 const SDL_Rect * rect, int markDirty, void **pixels,
                 int *pitch)
{
    GLES_TextureData *data = (GLES_TextureData *) texture->driverdata;

    if (markDirty) {
        SDL_AddDirtyRect(&data->dirty, rect);
    }

    *pixels =
        (void *) ((Uint8 *) data->pixels + rect->y * data->pitch +
                  rect->x * SDL_BYTESPERPIXEL(texture->format));
    *pitch = data->pitch;
    return 0;
}

static void
GLES_UnlockTexture(SDL_Renderer * renderer, SDL_Texture * texture)
{
}

static void
GLES_DirtyTexture(SDL_Renderer * renderer, SDL_Texture * texture,
                  int numrects, const SDL_Rect * rects)
{
    GLES_TextureData *data = (GLES_TextureData *) texture->driverdata;
    int i;

    for (i = 0; i < numrects; ++i) {
        SDL_AddDirtyRect(&data->dirty, &rects[i]);
    }
}

static int
GLES_RenderFill(SDL_Renderer * renderer, Uint8 r, Uint8 g, Uint8 b, Uint8 a,
                const SDL_Rect * rect)
{

    GLES_RenderData *data = (GLES_RenderData *) renderer->driverdata;
    SDL_Window *window = SDL_GetWindowFromID(renderer->window);

    /* set proper drawing color */
    GLfloat oldClearColor[4];

    data->glGetFloatv(GL_COLOR_CLEAR_VALUE, oldClearColor);

    data->glClearColor((GLclampf) r * inv255f, (GLclampf) g * inv255f,
                       (GLclampf) b * inv255f, (GLclampf) a * inv255f);

    data->glScissor(rect->x, window->h - rect->y - rect->h, rect->w, rect->h);
    data->glEnable(GL_SCISSOR_TEST);
    data->glClear(GL_COLOR_BUFFER_BIT);
    data->glDisable(GL_SCISSOR_TEST);

    /* reset clear color */
    data->glClearColor(oldClearColor[0], oldClearColor[1], oldClearColor[2],
                       oldClearColor[2]);

    return 0;
}

static int
GLES_RenderCopy(SDL_Renderer * renderer, SDL_Texture * texture,
                const SDL_Rect * srcrect, const SDL_Rect * dstrect)
{

    GLES_RenderData *data = (GLES_RenderData *) renderer->driverdata;
    GLES_TextureData *texturedata = (GLES_TextureData *) texture->driverdata;
    int minx, miny, maxx, maxy;
    GLfloat minu, maxu, minv, maxv;
    int i;
    void *temp_buffer;          /* used for reformatting dirty rect pixels */
    void *temp_ptr;

    if (texturedata->dirty.list) {
        SDL_DirtyRect *dirty;
        void *pixels;
        int bpp = SDL_BYTESPERPIXEL(texture->format);
        int pitch = texturedata->pitch;

        SetupTextureUpdate(data, texture, pitch);

        data->glBindTexture(texturedata->type, texturedata->texture);
        for (dirty = texturedata->dirty.list; dirty; dirty = dirty->next) {
            SDL_Rect *rect = &dirty->rect;
            pixels =
                (void *) ((Uint8 *) texturedata->pixels + rect->y * pitch +
                          rect->x * bpp);
            /*      There is no GL_UNPACK_ROW_LENGTH in OpenGLES 
               we must do this reformatting ourselves(!)

               maybe it'd be a good idea to keep a temp buffer around
               for this purpose rather than allocating it each time
             */
            temp_buffer = SDL_malloc(rect->w * rect->h * bpp);
            temp_ptr = temp_buffer;
            for (i = 0; i < rect->h; i++) {
                SDL_memcpy(temp_ptr, pixels, rect->w * bpp);
                temp_ptr += rect->w * bpp;
                pixels += pitch;
            }

            data->glTexSubImage2D(texturedata->type, 0, rect->x, rect->y,
                                  rect->w, rect->h, texturedata->format,
                                  texturedata->formattype, temp_buffer);

            SDL_free(temp_buffer);

        }
        SDL_ClearDirtyRects(&texturedata->dirty);
    }

    data->glBindTexture(texturedata->type, texturedata->texture);
    data->glEnable(GL_TEXTURE_2D);

    if (texture->modMode) {
        data->glColor4f((GLfloat) texture->r * inv255f,
                        (GLfloat) texture->g * inv255f,
                        (GLfloat) texture->b * inv255f,
                        (GLfloat) texture->a * inv255f);
    } else {
        data->glColor4f(1.0f, 1.0f, 1.0f, 1.0f);
    }

    if (texture->blendMode != data->blendMode) {
        switch (texture->blendMode) {
        case SDL_TEXTUREBLENDMODE_NONE:
            data->glTexEnvf(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_DECAL);
            data->glDisable(GL_BLEND);
            break;
        case SDL_TEXTUREBLENDMODE_MASK:
        case SDL_TEXTUREBLENDMODE_BLEND:
            data->glTexEnvf(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_MODULATE);
            data->glEnable(GL_BLEND);
            data->glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
            break;
        case SDL_TEXTUREBLENDMODE_ADD:
            data->glTexEnvf(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_MODULATE);
            data->glEnable(GL_BLEND);
            data->glBlendFunc(GL_SRC_ALPHA, GL_ONE);
            break;
        case SDL_TEXTUREBLENDMODE_MOD:
            data->glTexEnvf(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_MODULATE);
            data->glEnable(GL_BLEND);
            data->glBlendFunc(GL_ZERO, GL_SRC_COLOR);
            break;
        }
        data->blendMode = texture->blendMode;
    }

    switch (texture->scaleMode) {
    case SDL_TEXTURESCALEMODE_NONE:
    case SDL_TEXTURESCALEMODE_FAST:
        data->glTexParameteri(texturedata->type, GL_TEXTURE_MIN_FILTER,
                              GL_NEAREST);
        data->glTexParameteri(texturedata->type, GL_TEXTURE_MAG_FILTER,
                              GL_NEAREST);
        break;
    case SDL_TEXTURESCALEMODE_SLOW:
    case SDL_TEXTURESCALEMODE_BEST:
        data->glTexParameteri(texturedata->type, GL_TEXTURE_MIN_FILTER,
                              GL_LINEAR);
        data->glTexParameteri(texturedata->type, GL_TEXTURE_MAG_FILTER,
                              GL_LINEAR);
        break;
    }

    if (data->GL_OES_draw_texture_supported && data->useDrawTexture) {
        /* this code is a little funny because the viewport is upside down vs SDL's coordinate system */
        SDL_Window *window = SDL_GetWindowFromID(renderer->window);
        GLint cropRect[4];
        cropRect[0] = srcrect->x;
        cropRect[1] = srcrect->y + srcrect->h;
        cropRect[2] = srcrect->w;
        cropRect[3] = -srcrect->h;
        data->glTexParameteriv(GL_TEXTURE_2D, GL_TEXTURE_CROP_RECT_OES,
                               cropRect);
        data->glDrawTexiOES(dstrect->x, window->h - dstrect->y - dstrect->h,
                            0, dstrect->w, dstrect->h);
    } else {

        minx = dstrect->x;
        miny = dstrect->y;
        maxx = dstrect->x + dstrect->w;
        maxy = dstrect->y + dstrect->h;

        minu = (GLfloat) srcrect->x / texture->w;
        minu *= texturedata->texw;
        maxu = (GLfloat) (srcrect->x + srcrect->w) / texture->w;
        maxu *= texturedata->texw;
        minv = (GLfloat) srcrect->y / texture->h;
        minv *= texturedata->texh;
        maxv = (GLfloat) (srcrect->y + srcrect->h) / texture->h;
        maxv *= texturedata->texh;

        GLshort vertices[8];
        GLfloat texCoords[8];

        vertices[0] = minx;
        vertices[1] = miny;
        vertices[2] = maxx;
        vertices[3] = miny;
        vertices[4] = minx;
        vertices[5] = maxy;
        vertices[6] = maxx;
        vertices[7] = maxy;

        texCoords[0] = minu;
        texCoords[1] = minv;
        texCoords[2] = maxu;
        texCoords[3] = minv;
        texCoords[4] = minu;
        texCoords[5] = maxv;
        texCoords[6] = maxu;
        texCoords[7] = maxv;

        data->glVertexPointer(2, GL_SHORT, 0, vertices);
        data->glEnableClientState(GL_VERTEX_ARRAY);
        data->glTexCoordPointer(2, GL_FLOAT, 0, texCoords);
        data->glEnableClientState(GL_TEXTURE_COORD_ARRAY);
        data->glDrawArrays(GL_TRIANGLE_STRIP, 0, 4);

    }

    return 0;
}

static void
GLES_RenderPresent(SDL_Renderer * renderer)
{
    SDL_GL_SwapWindow(renderer->window);
}

static void
GLES_DestroyTexture(SDL_Renderer * renderer, SDL_Texture * texture)
{
    GLES_RenderData *renderdata = (GLES_RenderData *) renderer->driverdata;
    GLES_TextureData *data = (GLES_TextureData *) texture->driverdata;

    if (!data) {
        return;
    }
    if (data->texture) {
        glDeleteTextures(1, &data->texture);
    }
    if (data->pixels) {
        SDL_free(data->pixels);
    }
    SDL_FreeDirtyRects(&data->dirty);
    SDL_free(data);
    texture->driverdata = NULL;
}

static void
GLES_DestroyRenderer(SDL_Renderer * renderer)
{
    GLES_RenderData *data = (GLES_RenderData *) renderer->driverdata;

    if (data) {
        if (data->context) {
            /* SDL_GL_MakeCurrent(0, NULL); *//* doesn't do anything */
            SDL_GL_DeleteContext(data->context);
        }
        SDL_free(data);
    }
    SDL_free(renderer);
}

#endif /* SDL_VIDEO_RENDER_OGL */

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