Opengl：渲染到Win32 API上下文

Question

我正在嘗試創建一個opengl上下文（至少ogl 4.5）並渲染它; 它與SDL2一起工作正常，但我無法弄清楚為什么它不適用於Win32：我正在嘗試使用glClearColor（）/ glClear將屏幕顏色設置為RGBA（1,0,0,1），但似乎沒有任何事情發生。 這是我的代碼： - EDIT我按照你的建議更新了代碼，但似乎沒有渲染; 問題還不在於gl 3.x / 4.x功能，因為我在創建了一個擺動上下文后初始化了GLEW

LRESULT CALLBACK WndProc(HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam);
HGLRC ourOpenGLRenderingContext;
bool running = true;

int WinMain(__in HINSTANCE hInstance, __in_opt HINSTANCE hPrevInstance, __in_opt LPSTR lpCmdLine, __in int nShowCmd)
{
    MSG msg = { 0 };
    WNDCLASS wc = { 0 };
    wc.lpfnWndProc = WndProc;
    wc.hInstance = hInstance;
    wc.hbrBackground = (HBRUSH)(COLOR_BACKGROUND);
    wc.lpszClassName = L"oglversionchecksample";
    wc.style = CS_OWNDC;
    if (!RegisterClass(&wc))
        return 1;
    CreateWindowW(wc.lpszClassName, L"openglversioncheck",
        WS_OVERLAPPEDWINDOW | WS_VISIBLE, 0, 0, 640, 480, 0, 0, hInstance, 0);


        while (GetMessage(&msg, NULL, 0, 0) > 0)
            DispatchMessage(&msg);


    return 0;
}

LRESULT CALLBACK WndProc(HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam)
{
    switch (message)
    {
    case WM_PAINT:
        glViewport(0, 0, 100, 100); //render to a viewport of width (100; 100)
        glClearColor(1.0, 0.0, 0.0, 1.0);
        glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
        break;
    case WM_CREATE:
    {
        PIXELFORMATDESCRIPTOR pfd =
        {
            sizeof(PIXELFORMATDESCRIPTOR),
            1,
            PFD_DRAW_TO_WINDOW | PFD_SUPPORT_OPENGL | PFD_DOUBLEBUFFER,    //Flags
            PFD_TYPE_RGBA,            //The kind of framebuffer. RGBA or palette.
            32,                        //Colordepth of the framebuffer.
            0, 0, 0, 0, 0, 0,
            0,
            0,
            0,
            0, 0, 0, 0,
            24,                        //Number of bits for the depthbuffer
            8,                        //Number of bits for the stencilbuffer
            0,                        //Number of Aux buffers in the framebuffer.
            PFD_MAIN_PLANE,
            0,
            0, 0, 0
        };

        HDC ourWindowHandleToDeviceContext = GetDC(hWnd);

        int  letWindowsChooseThisPixelFormat;
        letWindowsChooseThisPixelFormat = ChoosePixelFormat(ourWindowHandleToDeviceContext, &pfd);
        SetPixelFormat(ourWindowHandleToDeviceContext, letWindowsChooseThisPixelFormat, &pfd);

        ourOpenGLRenderingContext = wglCreateContext(ourWindowHandleToDeviceContext);
        wglMakeCurrent(ourWindowHandleToDeviceContext, ourOpenGLRenderingContext);
        MessageBoxA(0, (char*)glGetString(GL_VERSION), "OPENGL VERSION", 0);

        if(glewInit() != GLEW_OK) {
            MessageBoxA(0, (char*)glGetString(GL_VERSION), "Error: Could not init OGL API (GLEW)", 0);
        }

    }
    break;
    case WM_CLOSE:
        //quit code
        wglDeleteContext(ourOpenGLRenderingContext);
        PostQuitMessage(0);
        break;
    default:
        return DefWindowProc(hWnd, message, wParam, lParam);
    }
    return 0;

}

Answer 1

在Windows中創建現代OpenGL渲染上下文需要更多的努力。 基本上，您首先必須創建一個代理上下文來加載必要的擴展，然后使用這些創建適當的上下文。 我寫了一個小型庫，在窗簾后面進行內部代理上下文管理，讓您無需進一步操作即可直接進入核心業務： http ： //github.com/datenwolf/wglarb

為了StackOverflow的最佳實踐，在answeres中包含代碼而不是鏈接這里的主要實現文件（它只有238行）：

/*
Copyright (c) 2014 Wolfgang 'datenwolf' Draxinger

Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in
all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
THE SOFTWARE.
*/
#include <GL/gl.h>
#include "wglarb.h"

#define wglarb_BuildAssert(cond) ((void)sizeof(char[1 - 2*!(cond)]))

static HANDLE wglarb_intermediary_mutex = NULL;

static DWORD wglarb_intermediary_lock(void)
{
    wglarb_BuildAssert( sizeof(PVOID) == sizeof(HANDLE) );

    if( !wglarb_intermediary_mutex ) {
        /* Between testing for the validity of the mutex handle,
         * creating a new mutex handle and using the interlocked
         * exchange there is a race... */

        /* //// START \\\\ */

        HANDLE const new_mutex =
            CreateMutex(NULL, TRUE, NULL);

        HANDLE const dst_mutex =
            InterlockedCompareExchangePointer(
                &wglarb_intermediary_mutex,
                new_mutex,
                NULL );

        /* //// FINISH \\\\ */

        if( !dst_mutex ) {
            /* mutex created in one time initialization and held
             * by calling thread. Return signaled status. */
            return WAIT_OBJECT_0;
        }
        /* In this case we lost the race and another thread
         * beat this thread in creating a mutex object.
         * Clean up and wait for the proper mutex. */
        ReleaseMutex(new_mutex);
        CloseHandle(new_mutex);
    }
    return WaitForSingleObject(wglarb_intermediary_mutex, INFINITE);
}

static BOOL wglarb_intermediary_unlock(void)
{
    return ReleaseMutex(wglarb_intermediary_mutex);
}

#define WGLARB_INTERMEDIARY_CLASS   "wglarb intermediary"
#define WGLARB_INTERMEDIARY_STYLE   (WS_CLIPSIBLINGS|WS_CLIPCHILDREN)
#define WGLARB_INTERMEDIARY_EXSTYLE 0

static HWND wglarb_intermediary_hWnd = 0;

static BOOL wglarb_intermediary_create_Wnd(void)
{
    HINSTANCE const hInstance = GetModuleHandle(NULL);

    WNDCLASS wc;
    memset(&wc,0,sizeof(wc));
    wc.hInstance = hInstance;
    wc.style = CS_HREDRAW|CS_VREDRAW|CS_OWNDC;
    wc.lpfnWndProc = DefWindowProc;
    wc.lpszClassName = WGLARB_INTERMEDIARY_CLASS;
    RegisterClass(&wc);

    wglarb_intermediary_hWnd =
        CreateWindowEx(
            WGLARB_INTERMEDIARY_EXSTYLE,
            WGLARB_INTERMEDIARY_CLASS,
            NULL,
            WGLARB_INTERMEDIARY_STYLE,
            0,0,0,0,
            NULL,NULL,
            hInstance,
            NULL );

    if( !wglarb_intermediary_hWnd ) {
        return FALSE;
    }

    return TRUE;
}

static HDC wglarb_intermediary_hDC = 0;

static BOOL wglarb_intermediary_create_DC(void)
{
    if( !wglarb_intermediary_hWnd
     && !wglarb_intermediary_create_Wnd() ) {
        return FALSE;
    }

    wglarb_intermediary_hDC = GetDC(wglarb_intermediary_hWnd);
    if( !wglarb_intermediary_hDC ) {
        return FALSE;
    }

    return TRUE;
}

static HGLRC wglarb_intermediary_hRC = 0;

static BOOL wglarb_intermediary_create_RC(void)
{
    if( !wglarb_intermediary_hDC
     && !wglarb_intermediary_create_DC() ) {
        return FALSE;
    }

    PIXELFORMATDESCRIPTOR pfd;
    memset(&pfd,0,sizeof(pfd));
    pfd.nSize = sizeof(pfd);
    pfd.nVersion = 1;
    pfd.dwFlags = PFD_SUPPORT_OPENGL|PFD_GENERIC_ACCELERATED|PFD_DRAW_TO_WINDOW;
    pfd.iPixelType = PFD_TYPE_RGBA;
    pfd.iLayerType = PFD_MAIN_PLANE;

    int iPF;
    if( !(iPF = ChoosePixelFormat(wglarb_intermediary_hDC, &pfd))
     || !(SetPixelFormat(wglarb_intermediary_hDC, iPF, &pfd))
     || !(wglarb_intermediary_hRC = wglCreateContext(wglarb_intermediary_hDC))
    ) {
        return FALSE;
    }

    return TRUE;
}

static BOOL wglarb_intermediary_makecurrent(HDC *hOrigDC, HGLRC *hOrigRC)
{
    *hOrigDC = wglGetCurrentDC();
    *hOrigRC = wglGetCurrentContext();

    if( !wglarb_intermediary_hRC
     && !wglarb_intermediary_create_RC() )  {
        return FALSE;
    }

    return wglMakeCurrent(wglarb_intermediary_hDC, wglarb_intermediary_hRC);
}

HGLRC WINAPI wglarb_CreateContextAttribsARB(
    HDC hDC,
    HGLRC hShareContext,
    const int *attribList)
{
    if( WAIT_OBJECT_0 != wglarb_intermediary_lock() ) {
        return NULL;
    }

    HDC   hOrigDC;
    HGLRC hOrigRC;
    if( !wglarb_intermediary_makecurrent(&hOrigDC, &hOrigRC) ) {
        wglarb_intermediary_unlock();
        return NULL;
    }

    PFNWGLCREATECONTEXTATTRIBSARBPROC impl =
        (PFNWGLCREATECONTEXTATTRIBSARBPROC)
            wglGetProcAddress("wglCreateContextAttribsARB");

    HGLRC ret = NULL;
    if( impl ) {
        ret = impl(hDC, hShareContext, attribList);
    }   

    wglMakeCurrent(hOrigDC, hOrigRC);
    wglarb_intermediary_unlock();
    return ret;
}

BOOL WINAPI wglarb_ChoosePixelFormatARB(
    HDC hdc,
    const int *piAttribIList,
    const FLOAT *pfAttribFList,
    UINT nMaxFormats,
    int *piFormats,
    UINT *nNumFormats)
{
    if( WAIT_OBJECT_0 != wglarb_intermediary_lock() ) {
        return FALSE;
    }

    HDC   hOrigDC;
    HGLRC hOrigRC;
    if( !wglarb_intermediary_makecurrent(&hOrigDC, &hOrigRC) ) {
        wglarb_intermediary_unlock();
        return FALSE;
    }

    PFNWGLCHOOSEPIXELFORMATARBPROC impl = NULL;

    impl = (PFNWGLCHOOSEPIXELFORMATARBPROC)
            wglGetProcAddress("wglChoosePixelFormatARB");
    if( !impl ) {
        /* WGL_EXT_pixel_format uses the same function prototypes
         * as the WGL_ARB_pixel_format extension */
        impl = (PFNWGLCHOOSEPIXELFORMATARBPROC)
                wglGetProcAddress("wglChoosePixelFormatEXT");
    }

    BOOL ret = FALSE;
    if( impl ) {
        ret = impl(
            hdc,
            piAttribIList,
            pfAttribFList,
            nMaxFormats,
            piFormats,
            nNumFormats );
    }   

    wglMakeCurrent(hOrigDC, hOrigRC);
    wglarb_intermediary_unlock();
    return ret;
}

Answer 2

查看SDL的代碼以了解它的作用 - 我認為在使用現代（> = 3或> = 4）OpenGL獲取上下文時會有些煩惱。

https://www.opengl.org/wiki/Creating_an_OpenGL_Context_%28WGL%29