src/video/windows/SDL_windowsopengl.c

/*
  Simple DirectMedia Layer
  Copyright (C) 1997-2011 Sam Lantinga <slouken@libsdl.org>

  This software is provided 'as-is', without any express or implied
  warranty.  In no event will the authors be held liable for any damages
  arising from the use of this software.

  Permission is granted to anyone to use this software for any purpose,
  including commercial applications, and to alter it and redistribute it
  freely, subject to the following restrictions:

  1. The origin of this software must not be misrepresented; you must not
     claim that you wrote the original software. If you use this software
     in a product, an acknowledgment in the product documentation would be
     appreciated but is not required.
  2. Altered source versions must be plainly marked as such, and must not be
     misrepresented as being the original software.
  3. This notice may not be removed or altered from any source distribution.
*/
#include "SDL_config.h"

#include "SDL_windowsvideo.h"

/* WGL implementation of SDL OpenGL support */

#if SDL_VIDEO_OPENGL_WGL
#include "SDL_opengl.h"

#define DEFAULT_OPENGL "OPENGL32.DLL"

#ifndef WGL_ARB_create_context
#define WGL_ARB_create_context
#define WGL_CONTEXT_MAJOR_VERSION_ARB   0x2091
#define WGL_CONTEXT_MINOR_VERSION_ARB   0x2092
#define WGL_CONTEXT_LAYER_PLANE_ARB     0x2093
#define WGL_CONTEXT_FLAGS_ARB           0x2093
#define WGL_CONTEXT_DEBUG_BIT_ARB       0x0001
#define WGL_CONTEXT_FORWARD_COMPATIBLE_BIT_ARB  0x0002
#endif

typedef HGLRC(APIENTRYP PFNWGLCREATECONTEXTATTRIBSARBPROC) (HDC hDC,
                                                            HGLRC
                                                            hShareContext,
                                                            const int
                                                            *attribList);

int
WIN_GL_LoadLibrary(_THIS, const char *path)
{
    LPTSTR wpath;
    HANDLE handle;

    if (path == NULL) {
        path = SDL_getenv("SDL_OPENGL_LIBRARY");
    }
    if (path == NULL) {
        path = DEFAULT_OPENGL;
    }
    wpath = WIN_UTF8ToString(path);
    _this->gl_config.dll_handle = LoadLibrary(wpath);
    SDL_free(wpath);
    if (!_this->gl_config.dll_handle) {
        char message[1024];
        SDL_snprintf(message, SDL_arraysize(message), "LoadLibrary(\"%s\")",
                     path);
        WIN_SetError(message);
        return -1;
    }
    SDL_strlcpy(_this->gl_config.driver_path, path,
                SDL_arraysize(_this->gl_config.driver_path));

    /* Allocate OpenGL memory */
    _this->gl_data =
        (struct SDL_GLDriverData *) SDL_calloc(1,
                                               sizeof(struct
                                                      SDL_GLDriverData));
    if (!_this->gl_data) {
        SDL_OutOfMemory();
        return -1;
    }

    /* Load function pointers */
    handle = _this->gl_config.dll_handle;
    _this->gl_data->wglGetProcAddress = (void *(WINAPI *) (const char *))
        GetProcAddress(handle, "wglGetProcAddress");
    _this->gl_data->wglCreateContext = (HGLRC(WINAPI *) (HDC))
        GetProcAddress(handle, "wglCreateContext");
    _this->gl_data->wglDeleteContext = (BOOL(WINAPI *) (HGLRC))
        GetProcAddress(handle, "wglDeleteContext");
    _this->gl_data->wglMakeCurrent = (BOOL(WINAPI *) (HDC, HGLRC))
        GetProcAddress(handle, "wglMakeCurrent");
    _this->gl_data->wglSwapIntervalEXT = (void (WINAPI *) (int))
        GetProcAddress(handle, "wglSwapIntervalEXT");
    _this->gl_data->wglGetSwapIntervalEXT = (int (WINAPI *) (void))
        GetProcAddress(handle, "wglGetSwapIntervalEXT");

    if (!_this->gl_data->wglGetProcAddress ||
        !_this->gl_data->wglCreateContext ||
        !_this->gl_data->wglDeleteContext ||
        !_this->gl_data->wglMakeCurrent) {
        SDL_SetError("Could not retrieve OpenGL functions");
        SDL_UnloadObject(handle);
        return -1;
    }

    return 0;
}

void *
WIN_GL_GetProcAddress(_THIS, const char *proc)
{
    void *func;

    /* This is to pick up extensions */
    func = _this->gl_data->wglGetProcAddress(proc);
    if (!func) {
        /* This is probably a normal GL function */
        func = GetProcAddress(_this->gl_config.dll_handle, proc);
    }
    return func;
}

void
WIN_GL_UnloadLibrary(_THIS)
{
    FreeLibrary((HMODULE) _this->gl_config.dll_handle);
    _this->gl_config.dll_handle = NULL;

    /* Free OpenGL memory */
    SDL_free(_this->gl_data);
    _this->gl_data = NULL;
}

static void
WIN_GL_SetupPixelFormat(_THIS, PIXELFORMATDESCRIPTOR * pfd)
{
    SDL_zerop(pfd);
    pfd->nSize = sizeof(*pfd);
    pfd->nVersion = 1;
    pfd->dwFlags = (PFD_DRAW_TO_WINDOW | PFD_SUPPORT_OPENGL);
    if (_this->gl_config.double_buffer) {
        pfd->dwFlags |= PFD_DOUBLEBUFFER;
    }
    if (_this->gl_config.stereo) {
        pfd->dwFlags |= PFD_STEREO;
    }
    pfd->iLayerType = PFD_MAIN_PLANE;
    pfd->iPixelType = PFD_TYPE_RGBA;
    pfd->cRedBits = _this->gl_config.red_size;
    pfd->cGreenBits = _this->gl_config.green_size;
    pfd->cBlueBits = _this->gl_config.blue_size;
    pfd->cAlphaBits = _this->gl_config.alpha_size;
    if (_this->gl_config.buffer_size) {
        pfd->cColorBits =
            _this->gl_config.buffer_size - _this->gl_config.alpha_size;
    } else {
        pfd->cColorBits = (pfd->cRedBits + pfd->cGreenBits + pfd->cBlueBits);
    }
    pfd->cAccumRedBits = _this->gl_config.accum_red_size;
    pfd->cAccumGreenBits = _this->gl_config.accum_green_size;
    pfd->cAccumBlueBits = _this->gl_config.accum_blue_size;
    pfd->cAccumAlphaBits = _this->gl_config.accum_alpha_size;
    pfd->cAccumBits =
        (pfd->cAccumRedBits + pfd->cAccumGreenBits + pfd->cAccumBlueBits +
         pfd->cAccumAlphaBits);
    pfd->cDepthBits = _this->gl_config.depth_size;
    pfd->cStencilBits = _this->gl_config.stencil_size;
}

/* Choose the closest pixel format that meets or exceeds the target.
   FIXME: Should we weight any particular attribute over any other?
*/
static int
WIN_GL_ChoosePixelFormat(HDC hdc, PIXELFORMATDESCRIPTOR * target)
{
    PIXELFORMATDESCRIPTOR pfd;
    int count, index, best = 0;
    unsigned int dist, best_dist = ~0U;

    count = DescribePixelFormat(hdc, 1, sizeof(pfd), NULL);

    for (index = 1; index <= count; index++) {

        if (!DescribePixelFormat(hdc, index, sizeof(pfd), &pfd)) {
            continue;
        }

        if ((pfd.dwFlags & target->dwFlags) != target->dwFlags) {
            continue;
        }

        if (pfd.iLayerType != target->iLayerType) {
            continue;
        }
        if (pfd.iPixelType != target->iPixelType) {
            continue;
        }

        dist = 0;

        if (pfd.cColorBits < target->cColorBits) {
            continue;
        } else {
            dist += (pfd.cColorBits - target->cColorBits);
        }
        if (pfd.cRedBits < target->cRedBits) {
            continue;
        } else {
            dist += (pfd.cRedBits - target->cRedBits);
        }
        if (pfd.cGreenBits < target->cGreenBits) {
            continue;
        } else {
            dist += (pfd.cGreenBits - target->cGreenBits);
        }
        if (pfd.cBlueBits < target->cBlueBits) {
            continue;
        } else {
            dist += (pfd.cBlueBits - target->cBlueBits);
        }
        if (pfd.cAlphaBits < target->cAlphaBits) {
            continue;
        } else {
            dist += (pfd.cAlphaBits - target->cAlphaBits);
        }
        if (pfd.cAccumBits < target->cAccumBits) {
            continue;
        } else {
            dist += (pfd.cAccumBits - target->cAccumBits);
        }
        if (pfd.cAccumRedBits < target->cAccumRedBits) {
            continue;
        } else {
            dist += (pfd.cAccumRedBits - target->cAccumRedBits);
        }
        if (pfd.cAccumGreenBits < target->cAccumGreenBits) {
            continue;
        } else {
            dist += (pfd.cAccumGreenBits - target->cAccumGreenBits);
        }
        if (pfd.cAccumBlueBits < target->cAccumBlueBits) {
            continue;
        } else {
            dist += (pfd.cAccumBlueBits - target->cAccumBlueBits);
        }
        if (pfd.cAccumAlphaBits < target->cAccumAlphaBits) {
            continue;
        } else {
            dist += (pfd.cAccumAlphaBits - target->cAccumAlphaBits);
        }
        if (pfd.cDepthBits < target->cDepthBits) {
            continue;
        } else {
            dist += (pfd.cDepthBits - target->cDepthBits);
        }
        if (pfd.cStencilBits < target->cStencilBits) {
            continue;
        } else {
            dist += (pfd.cStencilBits - target->cStencilBits);
        }

        if (dist < best_dist) {
            best = index;
            best_dist = dist;
        }
    }

    return best;
}

static SDL_bool
HasExtension(const char *extension, const char *extensions)
{
    const char *start;
    const char *where, *terminator;

    /* Extension names should not have spaces. */
    where = SDL_strchr(extension, ' ');
    if (where || *extension == '\0')
        return SDL_FALSE;

    if (!extensions)
        return SDL_FALSE;

    /* It takes a bit of care to be fool-proof about parsing the
     * OpenGL extensions string. Don't be fooled by sub-strings,
     * etc. */

    start = extensions;

    for (;;) {
        where = SDL_strstr(start, extension);
        if (!where)
            break;

        terminator = where + SDL_strlen(extension);
        if (where == start || *(where - 1) == ' ')
            if (*terminator == ' ' || *terminator == '\0')
                return SDL_TRUE;

        start = terminator;
    }
    return SDL_FALSE;
}

static void
WIN_GL_InitExtensions(_THIS, HDC hdc)
{
    const char *(WINAPI * wglGetExtensionsStringARB) (HDC) = 0;
    const char *extensions;

    wglGetExtensionsStringARB = (const char *(WINAPI *) (HDC))
        _this->gl_data->wglGetProcAddress("wglGetExtensionsStringARB");
    if (wglGetExtensionsStringARB) {
        extensions = wglGetExtensionsStringARB(hdc);
    } else {
        extensions = NULL;
    }

    /* Check for WGL_ARB_pixel_format */
    _this->gl_data->WGL_ARB_pixel_format = 0;
    if (HasExtension("WGL_ARB_pixel_format", extensions)) {
        _this->gl_data->wglChoosePixelFormatARB = (BOOL(WINAPI *)
                                                   (HDC, const int *,
                                                    const FLOAT *, UINT,
                                                    int *, UINT *))
            WIN_GL_GetProcAddress(_this, "wglChoosePixelFormatARB");
        _this->gl_data->wglGetPixelFormatAttribivARB =
            (BOOL(WINAPI *) (HDC, int, int, UINT, const int *, int *))
            WIN_GL_GetProcAddress(_this, "wglGetPixelFormatAttribivARB");

        if ((_this->gl_data->wglChoosePixelFormatARB != NULL) &&
            (_this->gl_data->wglGetPixelFormatAttribivARB != NULL)) {
            _this->gl_data->WGL_ARB_pixel_format = 1;
        }
    }

    /* Check for WGL_EXT_swap_control */
    if (HasExtension("WGL_EXT_swap_control", extensions)) {
        _this->gl_data->wglSwapIntervalEXT =
            WIN_GL_GetProcAddress(_this, "wglSwapIntervalEXT");
        _this->gl_data->wglGetSwapIntervalEXT =
            WIN_GL_GetProcAddress(_this, "wglGetSwapIntervalEXT");
    } else {
        _this->gl_data->wglSwapIntervalEXT = NULL;
        _this->gl_data->wglGetSwapIntervalEXT = NULL;
    }
}

static int
WIN_GL_ChoosePixelFormatARB(_THIS, int *iAttribs, float *fAttribs)
{
    HWND hwnd;
    HDC hdc;
    PIXELFORMATDESCRIPTOR pfd;
    HGLRC hglrc;
    int pixel_format = 0;
    unsigned int matching;

    hwnd =
        CreateWindow(SDL_Appname, SDL_Appname, (WS_POPUP | WS_DISABLED), 0, 0,
                     10, 10, NULL, NULL, SDL_Instance, NULL);
    WIN_PumpEvents(_this);

    hdc = GetDC(hwnd);

    WIN_GL_SetupPixelFormat(_this, &pfd);

    SetPixelFormat(hdc, ChoosePixelFormat(hdc, &pfd), &pfd);

    hglrc = _this->gl_data->wglCreateContext(hdc);
    if (hglrc) {
        _this->gl_data->wglMakeCurrent(hdc, hglrc);

        WIN_GL_InitExtensions(_this, hdc);

        if (_this->gl_data->WGL_ARB_pixel_format) {
            _this->gl_data->wglChoosePixelFormatARB(hdc, iAttribs, fAttribs,
                                                    1, &pixel_format,
                                                    &matching);
        }

        _this->gl_data->wglMakeCurrent(NULL, NULL);
        _this->gl_data->wglDeleteContext(hglrc);
    }
    ReleaseDC(hwnd, hdc);
    DestroyWindow(hwnd);
    WIN_PumpEvents(_this);

    return pixel_format;
}

int
WIN_GL_SetupWindow(_THIS, SDL_Window * window)
{
    HDC hdc = ((SDL_WindowData *) window->driverdata)->hdc;
    PIXELFORMATDESCRIPTOR pfd;
    int pixel_format;
    int iAttribs[64];
    int *iAttr;
    float fAttribs[1] = { 0 };

    WIN_GL_SetupPixelFormat(_this, &pfd);

    /* setup WGL_ARB_pixel_format attribs */
    iAttr = &iAttribs[0];

    *iAttr++ = WGL_DRAW_TO_WINDOW_ARB;
    *iAttr++ = GL_TRUE;
    *iAttr++ = WGL_RED_BITS_ARB;
    *iAttr++ = _this->gl_config.red_size;
    *iAttr++ = WGL_GREEN_BITS_ARB;
    *iAttr++ = _this->gl_config.green_size;
    *iAttr++ = WGL_BLUE_BITS_ARB;
    *iAttr++ = _this->gl_config.blue_size;

    if (_this->gl_config.alpha_size) {
        *iAttr++ = WGL_ALPHA_BITS_ARB;
        *iAttr++ = _this->gl_config.alpha_size;
    }

    *iAttr++ = WGL_DOUBLE_BUFFER_ARB;
    *iAttr++ = _this->gl_config.double_buffer;

    *iAttr++ = WGL_DEPTH_BITS_ARB;
    *iAttr++ = _this->gl_config.depth_size;

    if (_this->gl_config.stencil_size) {
        *iAttr++ = WGL_STENCIL_BITS_ARB;
        *iAttr++ = _this->gl_config.stencil_size;
    }

    if (_this->gl_config.accum_red_size) {
        *iAttr++ = WGL_ACCUM_RED_BITS_ARB;
        *iAttr++ = _this->gl_config.accum_red_size;
    }

    if (_this->gl_config.accum_green_size) {
        *iAttr++ = WGL_ACCUM_GREEN_BITS_ARB;
        *iAttr++ = _this->gl_config.accum_green_size;
    }

    if (_this->gl_config.accum_blue_size) {
        *iAttr++ = WGL_ACCUM_BLUE_BITS_ARB;
        *iAttr++ = _this->gl_config.accum_blue_size;
    }

    if (_this->gl_config.accum_alpha_size) {
        *iAttr++ = WGL_ACCUM_ALPHA_BITS_ARB;
        *iAttr++ = _this->gl_config.accum_alpha_size;
    }

    if (_this->gl_config.stereo) {
        *iAttr++ = WGL_STEREO_ARB;
        *iAttr++ = GL_TRUE;
    }

    if (_this->gl_config.multisamplebuffers) {
        *iAttr++ = WGL_SAMPLE_BUFFERS_ARB;
        *iAttr++ = _this->gl_config.multisamplebuffers;
    }

    if (_this->gl_config.multisamplesamples) {
        *iAttr++ = WGL_SAMPLES_ARB;
        *iAttr++ = _this->gl_config.multisamplesamples;
    }

    *iAttr++ = WGL_ACCELERATION_ARB;
    *iAttr++ = (_this->gl_config.accelerated ? WGL_FULL_ACCELERATION_ARB :
                                               WGL_NO_ACCELERATION_ARB);

    *iAttr = 0;

    /* Choose and set the closest available pixel format */
    pixel_format = WIN_GL_ChoosePixelFormatARB(_this, iAttribs, fAttribs);
    if (!pixel_format) {
        pixel_format = WIN_GL_ChoosePixelFormat(hdc, &pfd);
    }
    if (!pixel_format) {
        SDL_SetError("No matching GL pixel format available");
        return -1;
    }
    if (!SetPixelFormat(hdc, pixel_format, &pfd)) {
        WIN_SetError("SetPixelFormat()");
        return (-1);
    }
    return 0;
}

SDL_GLContext
WIN_GL_CreateContext(_THIS, SDL_Window * window)
{
    HDC hdc = ((SDL_WindowData *) window->driverdata)->hdc;
    HGLRC context;

    if (_this->gl_config.major_version < 3) {
        context = _this->gl_data->wglCreateContext(hdc);
    } else {
        PFNWGLCREATECONTEXTATTRIBSARBPROC wglCreateContextAttribsARB;
        HGLRC temp_context = _this->gl_data->wglCreateContext(hdc);
        if (!temp_context) {
            SDL_SetError("Could not create GL context");
            return NULL;
        }

        /* Make the context current */
        if (WIN_GL_MakeCurrent(_this, window, temp_context) < 0) {
            WIN_GL_DeleteContext(_this, temp_context);
            return NULL;
        }

        wglCreateContextAttribsARB =
            (PFNWGLCREATECONTEXTATTRIBSARBPROC) _this->gl_data->
            wglGetProcAddress("wglCreateContextAttribsARB");
        if (!wglCreateContextAttribsARB) {
            SDL_SetError("GL 3.x is not supported");
            context = temp_context;
        } else {
            int attribs[] = {
                WGL_CONTEXT_MAJOR_VERSION_ARB, _this->gl_config.major_version,
                WGL_CONTEXT_MINOR_VERSION_ARB, _this->gl_config.minor_version,
                0
            };
            /* Create the GL 3.x context */
            context = wglCreateContextAttribsARB(hdc, 0, attribs);
            /* Delete the GL 2.x context */
            _this->gl_data->wglDeleteContext(temp_context);
        }
    }

    if (!context) {
        WIN_SetError("Could not create GL context");
        return NULL;
    }

    if (WIN_GL_MakeCurrent(_this, window, context) < 0) {
        WIN_GL_DeleteContext(_this, context);
        return NULL;
    }

    WIN_GL_InitExtensions(_this, hdc);

    return context;
}

int
WIN_GL_MakeCurrent(_THIS, SDL_Window * window, SDL_GLContext context)
{
    HDC hdc;
    int status;

    if (window) {
        hdc = ((SDL_WindowData *) window->driverdata)->hdc;
    } else {
        hdc = NULL;
    }
    if (!_this->gl_data->wglMakeCurrent(hdc, (HGLRC) context)) {
        WIN_SetError("wglMakeCurrent()");
        status = -1;
    } else {
        status = 0;
    }
    return status;
}

int
WIN_GL_SetSwapInterval(_THIS, int interval)
{
    if (_this->gl_data->wglSwapIntervalEXT) {
        _this->gl_data->wglSwapIntervalEXT(interval);
        return 0;
    } else {
        SDL_Unsupported();
        return -1;
    }
}

int
WIN_GL_GetSwapInterval(_THIS)
{
    if (_this->gl_data->wglGetSwapIntervalEXT) {
        return _this->gl_data->wglGetSwapIntervalEXT();
    } else {
        SDL_Unsupported();
        return -1;
    }
}

void
WIN_GL_SwapWindow(_THIS, SDL_Window * window)
{
    HDC hdc = ((SDL_WindowData *) window->driverdata)->hdc;

    SwapBuffers(hdc);
}

void
WIN_GL_DeleteContext(_THIS, SDL_GLContext context)
{
    _this->gl_data->wglDeleteContext((HGLRC) context);
}

#endif /* SDL_VIDEO_OPENGL_WGL */

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