src/render/opengl/SDL_render_gl.c
changeset 5195 bb45ecd958d8
parent 5184 d976b67150c5
child 5203 25ffd4e5255c
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/render/opengl/SDL_render_gl.c	Sat Feb 05 12:01:11 2011 -0800
@@ -0,0 +1,826 @@
+/*
+    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/documentation/GraphicsImaging/Conceptual/OpenGL-MacProgGuide/opengl_texturedata/chapter_10_section_2.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_PRESENTVSYNC | SDL_RENDERER_ACCELERATED),
+     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 "../../video/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 "../../video/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;
+
+    if (GL_LoadFunctions(data) < 0) {
+        GL_DestroyRenderer(renderer);
+        return NULL;
+    }
+
+    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;
+    }
+#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_RGB888:
+    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 */
+
+/* vi: set ts=4 sw=4 expandtab: */