/*

    SDL - Simple DirectMedia Layer

    Copyright (C) 1997-2010 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

#include "SDL_opengl.h"

#include "../SDL_sysrender.h"

#ifdef __MACOSX__

#include <OpenGL/OpenGL.h>

#endif

/* OpenGL renderer implementation */

/* Details on optimizing the texture path on Mac OS X:

   http://developer.apple.com/library/mac/#documentation/GraphicsImaging/Conceptual/OpenGL-MacProgGuide/opengl_texturedata/opengl_texturedata.html

*/

/* Used to re-create the window with OpenGL capability */

extern int SDL_RecreateWindow(SDL_Window * window, Uint32 flags);

static const float inv255f = 1.0f / 255.0f;

static SDL_Renderer *GL_CreateRenderer(SDL_Window * window, Uint32 flags);

static void GL_WindowEvent(SDL_Renderer * renderer,

                           const SDL_WindowEvent *event);

static int GL_CreateTexture(SDL_Renderer * renderer, SDL_Texture * texture);

static int GL_UpdateTexture(SDL_Renderer * renderer, SDL_Texture * texture,

                            const SDL_Rect * rect, const void *pixels,

                            int pitch);

static int GL_LockTexture(SDL_Renderer * renderer, SDL_Texture * texture,

                          const SDL_Rect * rect, void **pixels, int *pitch);

static void GL_UnlockTexture(SDL_Renderer * renderer, SDL_Texture * texture);

static int GL_RenderClear(SDL_Renderer * renderer);

static int GL_RenderDrawPoints(SDL_Renderer * renderer,

                               const SDL_Point * points, int count);

static int GL_RenderDrawLines(SDL_Renderer * renderer,

                              const SDL_Point * points, int count);

static int GL_RenderFillRects(SDL_Renderer * renderer,

                              const SDL_Rect ** rects, int count);

static int GL_RenderCopy(SDL_Renderer * renderer, SDL_Texture * texture,

                         const SDL_Rect * srcrect, const SDL_Rect * dstrect);

static int GL_RenderReadPixels(SDL_Renderer * renderer, const SDL_Rect * rect,

                               Uint32 pixel_format, void * pixels, int pitch);

static void GL_RenderPresent(SDL_Renderer * renderer);

static void GL_DestroyTexture(SDL_Renderer * renderer, SDL_Texture * texture);

static void GL_DestroyRenderer(SDL_Renderer * renderer);

SDL_RenderDriver GL_RenderDriver = {

    GL_CreateRenderer,

    {

     "opengl",

     (SDL_RENDERER_ACCELERATED | SDL_RENDERER_PRESENTVSYNC),

     1,

     {SDL_PIXELFORMAT_ARGB8888},

     0,

     0}

};

typedef struct

{

    SDL_GLContext context;

    SDL_bool updateSize;

    SDL_bool GL_ARB_texture_rectangle_supported;

    int blendMode;

    /* OpenGL functions */

#define SDL_PROC(ret,func,params) ret (APIENTRY *func) params;

#include "SDL_glfuncs.h"

#undef SDL_PROC

    void (*glTextureRangeAPPLE) (GLenum target, GLsizei length,

                                 const GLvoid * pointer);

} GL_RenderData;

typedef struct

{

    GLuint texture;

    GLenum type;

    GLfloat texw;

    GLfloat texh;

    GLenum format;

    GLenum formattype;

    void *pixels;

    int pitch;

} GL_TextureData;

static void

GL_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;

    case GL_TABLE_TOO_LARGE:

        error = "GL_TABLE_TOO_LARGE";

        break;

    default:

        error = "UNKNOWN";

        break;

    }

    SDL_SetError("%s: %s", prefix, error);

}

static int

GL_LoadFunctions(GL_RenderData * data)

{

#ifdef __SDL_NOGETPROCADDR__

#define SDL_PROC(ret,func,params) data->func=func;

#else

#define SDL_PROC(ret,func,params) \

    do { \

        data->func = SDL_GL_GetProcAddress(#func); \

        if ( ! data->func ) { \

            SDL_SetError("Couldn't load GL function %s: %s\n", #func, SDL_GetError()); \

            return -1; \

        } \

    } while ( 0 );

#endif /* __SDL_NOGETPROCADDR__ */

#include "SDL_glfuncs.h"

#undef SDL_PROC

    return 0;

}

SDL_Renderer *

GL_CreateRenderer(SDL_Window * window, Uint32 flags)

{

    SDL_Renderer *renderer;

    GL_RenderData *data;

    GLint value;

    Uint32 window_flags;

    window_flags = SDL_GetWindowFlags(window);

    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 = (GL_RenderData *) SDL_calloc(1, sizeof(*data));

    if (!data) {

        GL_DestroyRenderer(renderer);

        SDL_OutOfMemory();

        return NULL;

    }

    renderer->WindowEvent = GL_WindowEvent;

    renderer->CreateTexture = GL_CreateTexture;

    renderer->UpdateTexture = GL_UpdateTexture;

    renderer->LockTexture = GL_LockTexture;

    renderer->UnlockTexture = GL_UnlockTexture;

    renderer->RenderClear = GL_RenderClear;

    renderer->RenderDrawPoints = GL_RenderDrawPoints;

    renderer->RenderDrawLines = GL_RenderDrawLines;

    renderer->RenderFillRects = GL_RenderFillRects;

    renderer->RenderCopy = GL_RenderCopy;

    renderer->RenderReadPixels = GL_RenderReadPixels;

    renderer->RenderPresent = GL_RenderPresent;

    renderer->DestroyTexture = GL_DestroyTexture;

    renderer->DestroyRenderer = GL_DestroyRenderer;

    renderer->info = GL_RenderDriver.info;

    renderer->driverdata = data;

    renderer->info.flags = SDL_RENDERER_ACCELERATED;

    data->context = SDL_GL_CreateContext(window);

    if (!data->context) {

        GL_DestroyRenderer(renderer);

        return NULL;

    }

    if (SDL_GL_MakeCurrent(window, data->context) < 0) {

        GL_DestroyRenderer(renderer);

        return NULL;

    }

    if (GL_LoadFunctions(data) < 0) {

        GL_DestroyRenderer(renderer);

        return NULL;

    }

#ifdef __MACOSX__

    /* Enable multi-threaded rendering */

    /* Disabled until Ryan finishes his VBO/PBO code...

       CGLEnable(CGLGetCurrentContext(), kCGLCEMPEngine);

     */

#endif

    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;

    }

    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;

    if (SDL_GL_ExtensionSupported("GL_ARB_texture_rectangle")

        || SDL_GL_ExtensionSupported("GL_EXT_texture_rectangle")) {

        data->GL_ARB_texture_rectangle_supported = SDL_TRUE;

    }

    if (SDL_GL_ExtensionSupported("GL_APPLE_texture_range")) {

        data->glTextureRangeAPPLE =

            (void (*)(GLenum, GLsizei, const GLvoid *))

            SDL_GL_GetProcAddress("glTextureRangeAPPLE");

    }

    /* Set up parameters for rendering */

    data->blendMode = -1;

    data->glDisable(GL_DEPTH_TEST);

    data->glDisable(GL_CULL_FACE);

    /* This ended up causing video discrepancies between OpenGL and Direct3D */

    /*data->glEnable(GL_LINE_SMOOTH);*/

    if (data->GL_ARB_texture_rectangle_supported) {

        data->glEnable(GL_TEXTURE_RECTANGLE_ARB);

    } else {

        data->glEnable(GL_TEXTURE_2D);

    }

    data->updateSize = SDL_TRUE;

    return renderer;

}

static SDL_GLContext SDL_CurrentContext = NULL;

static int

GL_ActivateRenderer(SDL_Renderer * renderer)

{

    GL_RenderData *data = (GL_RenderData *) renderer->driverdata;

    SDL_Window *window = renderer->window;

    if (SDL_CurrentContext != data->context) {

        if (SDL_GL_MakeCurrent(window, data->context) < 0) {

            return -1;

        }

        SDL_CurrentContext = data->context;

    }

    if (data->updateSize) {

        int w, h;

        SDL_GetWindowSize(window, &w, &h);

        data->glMatrixMode(GL_PROJECTION);

        data->glLoadIdentity();

        data->glMatrixMode(GL_MODELVIEW);

        data->glLoadIdentity();

        data->glViewport(0, 0, w, h);

        data->glOrtho(0.0, (GLdouble) w, (GLdouble) h, 0.0, 0.0, 1.0);

        data->updateSize = SDL_FALSE;

    }

    return 0;

}

static void

GL_WindowEvent(SDL_Renderer * renderer, const SDL_WindowEvent *event)

{

    GL_RenderData *data = (GL_RenderData *) renderer->driverdata;

    if (event->event == SDL_WINDOWEVENT_RESIZED) {

        /* Rebind the context to the window area and update matrices */

        SDL_CurrentContext = NULL;

        data->updateSize = SDL_TRUE;

    }

}

static __inline__ int

power_of_2(int input)

{

    int value = 1;

    while (value < input) {

        value <<= 1;

    }

    return value;

}

static __inline__ SDL_bool

convert_format(GL_RenderData *renderdata, Uint32 pixel_format,

               GLint* internalFormat, GLenum* format, GLenum* type)

{

    switch (pixel_format) {

    case SDL_PIXELFORMAT_ARGB8888:

        *internalFormat = GL_RGBA8;

        *format = GL_BGRA;

        *type = GL_UNSIGNED_INT_8_8_8_8_REV;

        break;

    default:

        return SDL_FALSE;

    }

    return SDL_TRUE;

}

static int

GL_CreateTexture(SDL_Renderer * renderer, SDL_Texture * texture)

{

    GL_RenderData *renderdata = (GL_RenderData *) renderer->driverdata;

    GL_TextureData *data;

    GLint internalFormat;

    GLenum format, type;

    int texture_w, texture_h;

    GLenum result;

    GL_ActivateRenderer(renderer);

    if (!convert_format(renderdata, texture->format, &internalFormat,

                        &format, &type)) {

        SDL_SetError("Texture format %s not supported by OpenGL",

                     SDL_GetPixelFormatName(texture->format));

        return -1;

    }

    data = (GL_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);

    if (renderdata->GL_ARB_texture_rectangle_supported) {

        data->type = GL_TEXTURE_RECTANGLE_ARB;

        texture_w = texture->w;

        texture_h = texture->h;

        data->texw = (GLfloat) texture_w;

        data->texh = (GLfloat) texture_h;

    } else {

        data->type = GL_TEXTURE_2D;

        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->glEnable(data->type);

    renderdata->glBindTexture(data->type, data->texture);

    renderdata->glTexParameteri(data->type, GL_TEXTURE_MIN_FILTER,

                                GL_LINEAR);

    renderdata->glTexParameteri(data->type, GL_TEXTURE_MAG_FILTER,

                                GL_LINEAR);

    renderdata->glTexParameteri(data->type, GL_TEXTURE_WRAP_S,

                                GL_CLAMP_TO_EDGE);

    renderdata->glTexParameteri(data->type, GL_TEXTURE_WRAP_T,

                                GL_CLAMP_TO_EDGE);

#ifdef __MACOSX__

#ifndef GL_TEXTURE_STORAGE_HINT_APPLE

#define GL_TEXTURE_STORAGE_HINT_APPLE       0x85BC

#endif

#ifndef STORAGE_CACHED_APPLE

#define STORAGE_CACHED_APPLE                0x85BE

#endif

#ifndef STORAGE_SHARED_APPLE

#define STORAGE_SHARED_APPLE                0x85BF

#endif

    if (texture->access == SDL_TEXTUREACCESS_STREAMING) {

        renderdata->glTexParameteri(data->type, GL_TEXTURE_STORAGE_HINT_APPLE,

                                    GL_STORAGE_SHARED_APPLE);

    } else {

        renderdata->glTexParameteri(data->type, GL_TEXTURE_STORAGE_HINT_APPLE,

                                    GL_STORAGE_CACHED_APPLE);

    }

    if (texture->access == SDL_TEXTUREACCESS_STREAMING

        && texture->format == SDL_PIXELFORMAT_ARGB8888) {

        renderdata->glPixelStorei(GL_UNPACK_CLIENT_STORAGE_APPLE, GL_TRUE);

        renderdata->glTexImage2D(data->type, 0, internalFormat, texture_w,

                                 texture_h, 0, format, type, data->pixels);

    }

    else

#endif

    {

        renderdata->glTexImage2D(data->type, 0, internalFormat, texture_w,

                                 texture_h, 0, format, type, NULL);

    }

    renderdata->glDisable(data->type);

    result = renderdata->glGetError();

    if (result != GL_NO_ERROR) {

        GL_SetError("glTexImage2D()", result);

        return -1;

    }

    return 0;

}

static void

SetupTextureUpdate(GL_RenderData * renderdata, SDL_Texture * texture,

                   int pitch)

{

    renderdata->glPixelStorei(GL_UNPACK_ALIGNMENT, 1);

    renderdata->glPixelStorei(GL_UNPACK_ROW_LENGTH,

                              (pitch / SDL_BYTESPERPIXEL(texture->format)));

}

static int

GL_UpdateTexture(SDL_Renderer * renderer, SDL_Texture * texture,

                 const SDL_Rect * rect, const void *pixels, int pitch)

{

    GL_RenderData *renderdata = (GL_RenderData *) renderer->driverdata;

    GL_TextureData *data = (GL_TextureData *) texture->driverdata;

    GLenum result;

    GL_ActivateRenderer(renderer);

    renderdata->glGetError();

    SetupTextureUpdate(renderdata, texture, pitch);

    renderdata->glEnable(data->type);

    renderdata->glBindTexture(data->type, data->texture);

    renderdata->glTexSubImage2D(data->type, 0, rect->x, rect->y, rect->w,

                                rect->h, data->format, data->formattype,

                                pixels);

    renderdata->glDisable(data->type);

    result = renderdata->glGetError();

    if (result != GL_NO_ERROR) {

        GL_SetError("glTexSubImage2D()", result);

        return -1;

    }

    return 0;

}

static int

GL_LockTexture(SDL_Renderer * renderer, SDL_Texture * texture,

               const SDL_Rect * rect, void **pixels, int *pitch)

{

    GL_TextureData *data = (GL_TextureData *) texture->driverdata;

    *pixels =

        (void *) ((Uint8 *) data->pixels + rect->y * data->pitch +

                  rect->x * SDL_BYTESPERPIXEL(texture->format));

    *pitch = data->pitch;

    return 0;

}

static void

GL_UnlockTexture(SDL_Renderer * renderer, SDL_Texture * texture)

{

    GL_RenderData *renderdata = (GL_RenderData *) renderer->driverdata;

    GL_TextureData *data = (GL_TextureData *) texture->driverdata;

    GL_ActivateRenderer(renderer);

    SetupTextureUpdate(renderdata, texture, data->pitch);

    renderdata->glEnable(data->type);

    renderdata->glBindTexture(data->type, data->texture);

    renderdata->glTexSubImage2D(data->type, 0, 0, 0, texture->w, texture->h,

                                data->format, data->formattype, data->pixels);

    renderdata->glDisable(data->type);

}

static void

GL_SetBlendMode(GL_RenderData * data, int blendMode)

{

    if (blendMode != data->blendMode) {

        switch (blendMode) {

        case SDL_BLENDMODE_NONE:

            data->glTexEnvf(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_REPLACE);

            data->glDisable(GL_BLEND);

            break;

        case SDL_BLENDMODE_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_BLENDMODE_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_BLENDMODE_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 = blendMode;

    }

}

static int

GL_RenderClear(SDL_Renderer * renderer)

{

    GL_RenderData *data = (GL_RenderData *) renderer->driverdata;

    GL_ActivateRenderer(renderer);

    data->glClearColor((GLfloat) renderer->r * inv255f,

                       (GLfloat) renderer->g * inv255f,

                       (GLfloat) renderer->b * inv255f,

                       (GLfloat) renderer->a * inv255f);

    data->glClear(GL_COLOR_BUFFER_BIT);

    return 0;

}

static int

GL_RenderDrawPoints(SDL_Renderer * renderer, const SDL_Point * points,

                    int count)

{

    GL_RenderData *data = (GL_RenderData *) renderer->driverdata;

    int i;

    GL_ActivateRenderer(renderer);

    GL_SetBlendMode(data, renderer->blendMode);

    data->glColor4f((GLfloat) renderer->r * inv255f,

                    (GLfloat) renderer->g * inv255f,

                    (GLfloat) renderer->b * inv255f,

                    (GLfloat) renderer->a * inv255f);

    data->glBegin(GL_POINTS);

    for (i = 0; i < count; ++i) {

        data->glVertex2f(0.5f + points[i].x, 0.5f + points[i].y);

    }

    data->glEnd();

    return 0;

}

static int

GL_RenderDrawLines(SDL_Renderer * renderer, const SDL_Point * points,

                   int count)

{

    GL_RenderData *data = (GL_RenderData *) renderer->driverdata;

    int i;

    GL_ActivateRenderer(renderer);

    GL_SetBlendMode(data, renderer->blendMode);

    data->glColor4f((GLfloat) renderer->r * inv255f,

                    (GLfloat) renderer->g * inv255f,

                    (GLfloat) renderer->b * inv255f,

                    (GLfloat) renderer->a * inv255f);

    if (count > 2 && 

        points[0].x == points[count-1].x && points[0].y == points[count-1].y) {

        data->glBegin(GL_LINE_LOOP);

        /* GL_LINE_LOOP takes care of the final segment */

        --count;

        for (i = 0; i < count; ++i) {

            data->glVertex2f(0.5f + points[i].x, 0.5f + points[i].y);

        }

        data->glEnd();

    } else {

#if defined(__APPLE__) || defined(__WIN32__)

#else

        int x1, y1, x2, y2;

#endif

        data->glBegin(GL_LINE_STRIP);

        for (i = 0; i < count; ++i) {

            data->glVertex2f(0.5f + points[i].x, 0.5f + points[i].y);

        }

        data->glEnd();

        /* The line is half open, so we need one more point to complete it.

         * http://www.opengl.org/documentation/specs/version1.1/glspec1.1/node47.html

         * If we have to, we can use vertical line and horizontal line textures

         * for vertical and horizontal lines, and then create custom textures

         * for diagonal lines and software render those.  It's terrible, but at

         * least it would be pixel perfect.

         */

        data->glBegin(GL_POINTS);

#if defined(__APPLE__) || defined(__WIN32__)

        /* Mac OS X and Windows seem to always leave the second point open */

        data->glVertex2f(0.5f + points[count-1].x, 0.5f + points[count-1].y);

#else

        /* Linux seems to leave the right-most or bottom-most point open */

        x1 = points[0].x;

        y1 = points[0].y;

        x2 = points[count-1].x;

        y2 = points[count-1].y;

        if (x1 > x2) {

            data->glVertex2f(0.5f + x1, 0.5f + y1);

        } else if (x2 > x1) {

            data->glVertex2f(0.5f + x2, 0.5f + y2);

        } else if (y1 > y2) {

            data->glVertex2f(0.5f + x1, 0.5f + y1);

        } else if (y2 > y1) {

            data->glVertex2f(0.5f + x2, 0.5f + y2);

        }

#endif

        data->glEnd();

    }

    return 0;

}

static int

GL_RenderFillRects(SDL_Renderer * renderer, const SDL_Rect ** rects, int count)

{

    GL_RenderData *data = (GL_RenderData *) renderer->driverdata;

    int i;

    GL_ActivateRenderer(renderer);

    GL_SetBlendMode(data, renderer->blendMode);

    data->glColor4f((GLfloat) renderer->r * inv255f,

                    (GLfloat) renderer->g * inv255f,

                    (GLfloat) renderer->b * inv255f,

                    (GLfloat) renderer->a * inv255f);

    for (i = 0; i < count; ++i) {

        const SDL_Rect *rect = rects[i];

        data->glRecti(rect->x, rect->y, rect->x + rect->w, rect->y + rect->h);

    }

    return 0;

}

static int

GL_RenderCopy(SDL_Renderer * renderer, SDL_Texture * texture,

              const SDL_Rect * srcrect, const SDL_Rect * dstrect)

{

    GL_RenderData *data = (GL_RenderData *) renderer->driverdata;

    GL_TextureData *texturedata = (GL_TextureData *) texture->driverdata;

    int minx, miny, maxx, maxy;

    GLfloat minu, maxu, minv, maxv;

    GL_ActivateRenderer(renderer);

    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;

    data->glEnable(texturedata->type);

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

    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);

    }

    GL_SetBlendMode(data, texture->blendMode);

    data->glBegin(GL_TRIANGLE_STRIP);

    data->glTexCoord2f(minu, minv);

    data->glVertex2f((GLfloat) minx, (GLfloat) miny);

    data->glTexCoord2f(maxu, minv);

    data->glVertex2f((GLfloat) maxx, (GLfloat) miny);

    data->glTexCoord2f(minu, maxv);

    data->glVertex2f((GLfloat) minx, (GLfloat) maxy);

    data->glTexCoord2f(maxu, maxv);

    data->glVertex2f((GLfloat) maxx, (GLfloat) maxy);

    data->glEnd();

    data->glDisable(texturedata->type);

    return 0;

}

static int

GL_RenderReadPixels(SDL_Renderer * renderer, const SDL_Rect * rect,

                    Uint32 pixel_format, void * pixels, int pitch)

{

    GL_RenderData *data = (GL_RenderData *) renderer->driverdata;

    SDL_Window *window = renderer->window;

    GLint internalFormat;

    GLenum format, type;

    Uint8 *src, *dst, *tmp;

    int w, h, length, rows;

    GL_ActivateRenderer(renderer);

    if (!convert_format(data, pixel_format, &internalFormat, &format, &type)) {

        /* FIXME: Do a temp copy to a format that is supported */

        SDL_SetError("Unsupported pixel format");

        return -1;

    }

    SDL_GetWindowSize(window, &w, &h);

    data->glPixelStorei(GL_PACK_ALIGNMENT, 1);

    data->glPixelStorei(GL_PACK_ROW_LENGTH,

                        (pitch / SDL_BYTESPERPIXEL(pixel_format)));

    data->glReadPixels(rect->x, (h-rect->y)-rect->h, rect->w, rect->h,

                       format, type, pixels);

    /* Flip the rows to be top-down */

    length = rect->w * SDL_BYTESPERPIXEL(pixel_format);

    src = (Uint8*)pixels + (rect->h-1)*pitch;

    dst = (Uint8*)pixels;

    tmp = SDL_stack_alloc(Uint8, length);

    rows = rect->h / 2;

    while (rows--) {

        SDL_memcpy(tmp, dst, length);

        SDL_memcpy(dst, src, length);

        SDL_memcpy(src, tmp, length);

        dst += pitch;

        src -= pitch;

    }

    SDL_stack_free(tmp);

    return 0;

}

static void

GL_RenderPresent(SDL_Renderer * renderer)

{

    GL_ActivateRenderer(renderer);

    SDL_GL_SwapWindow(renderer->window);

}

static void

GL_DestroyTexture(SDL_Renderer * renderer, SDL_Texture * texture)

{

    GL_RenderData *renderdata = (GL_RenderData *) renderer->driverdata;

    GL_TextureData *data = (GL_TextureData *) texture->driverdata;

    GL_ActivateRenderer(renderer);

    if (!data) {

        return;

    }

    if (data->texture) {

        renderdata->glDeleteTextures(1, &data->texture);

    }

    if (data->pixels) {

        SDL_free(data->pixels);

    }

    SDL_free(data);

    texture->driverdata = NULL;

}

static void

GL_DestroyRenderer(SDL_Renderer * renderer)

{

    GL_RenderData *data = (GL_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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