所以我正在我的 Win32 应用程序中设置我的 OpenGL 上下文。我正在设置一个多线程环境，在一个线程中处理窗口消息，在另一个线程中调用 OpenGL 渲染。到目前为止，我的工作流程如下:
线程 A:
- 创建窗口
- 获取显示上下文
- 选择像素格式
- 创建一个临时的 OpenGL 上下文并使其成为当前上下文
- 获取扩展函数指针
- 将当前上下文设置为 NULL 并删除临时上下文
- 使用 wglCreateContextAttribsARB 创建一个新的上下文
- 启动线程 B
然后，在线程 B 中:
- wglMakeCurrent 使用来自线程 A 的 hdc 和 hglrc
问题是，线程 B 中的 wglMakeCurrent 返回 false，getLastError 返回 170(资源正在使用中)。我读过的所有内容都暗示这意味着渲染上下文已经在线程 A 中使用，但我什至在创建线程 B 之前就在线程 A 中明确调用了“wglMakeCurrent(NULL, NULL)”。
可能出了什么问题？
附言。为了清楚起见，我并没有尝试从不同的并发线程运行 OpenGL 调用。除了在线程 B 存在之前创建渲染上下文之外，每个单独的 OpenGL 调用都将从线程 B 进行。
编辑:这是一些源代码。这是在线程 A 中初始化窗口的函数:
Window* Window::init(void)
{
/* If the singleton exists already, just return a pointer to it */
if (singleton)
return singleton;
/* Allocate the singleton and check for errors */
singleton = new Window();
if (singleton == NULL)
{
fatalerror("In Window::init():\n");
fatalmore("Memory allocation failure.\n");
fatalmore("Could not allocate singleton.\n");
_getch();
exit(1);
}
/* Register window class */
WNDCLASSEX wc;
memset(&wc, 0, sizeof(WNDCLASSEX));
wc.cbSize = sizeof(WNDCLASSEX);
wc.style = CS_OWNDC | CS_HREDRAW | CS_VREDRAW;
wc.lpfnWndProc = wndProc;
wc.hInstance = GetModuleHandle(NULL);
wc.hIcon = LoadIcon(NULL, IDI_APPLICATION);
wc.hCursor = LoadCursor(NULL, IDC_ARROW);
wc.lpszClassName = APP_NAME;
if (!RegisterClassEx(&wc))
{
fatalerror("In Window::init():\n");
fatalmore("Failed to register window class.\n");
fatalmore("Error code: '%i'\n", GetLastError());
clean();
_getch();
exit(1);
}
/* Read settings */
int width = Settings::get()->screenWidth;
int height = Settings::get()->screenHeight;
DWORD exStyle = WS_EX_APPWINDOW | WS_EX_WINDOWEDGE;
DWORD style = WS_OVERLAPPEDWINDOW;
/* Are we using fullscreen mode? */
if (Settings::get()->fullscreen)
{
width = Settings::get()->fullscreenWidth;
height = Settings::get()->fullscreenHeight;
DEVMODE dm;
memset(&dm, 0, sizeof(DEVMODE));
dm.dmSize = sizeof(DEVMODE);
dm.dmPelsWidth = width;
dm.dmPelsHeight = height;
dm.dmBitsPerPel = 32;
dm.dmFields = DM_BITSPERPEL | DM_PELSWIDTH | DM_PELSHEIGHT;
if (ChangeDisplaySettings(&dm, CDS_FULLSCREEN) != DISP_CHANGE_SUCCESSFUL)
{
warning("in Window::init():\n");
warnmore("The requested fullscreen mode is not supported.\n");
warnmore("Will continue in windowed mode.\n");
width = Settings::get()->screenWidth;
height = Settings::get()->screenHeight;
Settings::get()->fullscreen = false;
}
else
{
exStyle = WS_EX_APPWINDOW;
style = WS_POPUP;
}
}
/* Create the window */
singleton->wnd = CreateWindowEx( exStyle,
APP_NAME, APP_NAME,
WS_OVERLAPPEDWINDOW | WS_CLIPCHILDREN | WS_CLIPSIBLINGS | style,
CW_USEDEFAULT, CW_USEDEFAULT,
width, height,
NULL,
NULL,
GetModuleHandle(NULL),
NULL );
if (!singleton->wnd)
{
fatalerror("In Window::init():\n");
fatalmore("Could not create window.\n");
fatalmore("Error code: '%i'\n", GetLastError());
clean();
_getch();
exit(1);
}
/* Get the DC */
singleton->dc = GetDC(singleton->wnd);
if (!singleton->dc)
{
fatalerror("In Window::init():\n");
fatalmore("Failed to get display context.\n");
fatalmore("Error code: '%i'\n", GetLastError());
clean();
_getch();
exit(1);
}
/* Choose a pixel format */
PIXELFORMATDESCRIPTOR pfd;
memset(&pfd, 0, sizeof(PIXELFORMATDESCRIPTOR));
pfd.nSize = sizeof(PIXELFORMATDESCRIPTOR);
pfd.nVersion = 1;
pfd.dwFlags = PFD_DRAW_TO_WINDOW | PFD_SUPPORT_OPENGL | PFD_DOUBLEBUFFER;
pfd.iPixelType = PFD_TYPE_RGBA;
pfd.cColorBits = 32;
pfd.cDepthBits = 24;
pfd.cStencilBits = 8;
pfd.iLayerType = PFD_MAIN_PLANE;
int pf = ChoosePixelFormat(singleton->dc, &pfd);
if (!pf)
{
fatalerror("In Window::init():\n");
fatalmore("Failed to choose a pixel format.\n");
fatalmore("Error code: '%i'\n", GetLastError());
clean();
_getch();
exit(1);
}
/* Set the pixel format */
if (!SetPixelFormat(singleton->dc, pf, &pfd))
{
fatalerror("In Window::init():\n");
fatalmore("Failed to set pixel format '%i'.\n", pf);
fatalmore("Error code: '%i'\n", GetLastError());
clean();
_getch();
exit(1);
}
/* Create our fake, temporary OpenGL context */
HGLRC temprc = wglCreateContext(singleton->dc);
if (!temprc)
{
fatalerror("In Window::init():\n");
fatalmore("Failed to create a temporary context.\n");
fatalmore("Error code: '%i'\n", GetLastError());
clean();
_getch();
exit(1);
}
wglMakeCurrent(singleton->dc, temprc);
/* Initialize the OpenGL extensions we need */
if (!initGLCreationExtensions())
{
fatalerror("In Window::init():\n");
fatalmore("Failed to initialize OpenGL context creation extensions.\n");
clean();
_getch();
exit(1);
}
/* Check for OpenGL version */
int majorver = 0, minorver = 0;
glGetIntegerv(GL_MAJOR_VERSION, &majorver);
glGetIntegerv(GL_MINOR_VERSION, &minorver);
if (majorver < 3 || (majorver == 3 && minorver < 1))
{
fatalerror("In Window::init():\n");
fatalmore("OpenGL version 3.1 or higher is required.\n");
clean();
_getch();
exit(1);
}
/* Define context attributes */
int contextAttribs[] =
{
WGL_CONTEXT_MAJOR_VERSION_ARB, majorver,
WGL_CONTEXT_MINOR_VERSION_ARB, minorver,
WGL_CONTEXT_PROFILE_MASK_ARB, WGL_CONTEXT_CORE_PROFILE_BIT_ARB,
WGL_CONTEXT_FLAGS_ARB, WGL_CONTEXT_FORWARD_COMPATIBLE_BIT_ARB,
0
};
/* Create the real OpenGL context */
singleton->rc = wglCreateContextAttribsARB(singleton->dc, NULL, contextAttribs);
if (!singleton->rc)
{
fatalerror("In Window::init():\n");
fatalmore("Failed to create OpenGL context.\n");
fatalmore("Error code: '%i'\n", GetLastError());
clean();
_getch();
exit(1);
}
ShowWindow(singleton->wnd, SW_SHOW);
/* Delete the fake context */
wglMakeCurrent(NULL, NULL);
wglDeleteContext(temprc);
info("Successfully created window.\n");
printf("\n");
return singleton;
}
这是在线程 B 中运行的启动函数:
bool Window::renderThreadStartupFunc(void)
{
if (!singleton)
return false;
if (!singleton->dc)
return false;
if (!wglMakeCurrent(singleton->dc, singleton->rc))
{
error("In Window::renderThreadStartupFunc():\n");
errormore("Could not make context current.\n");
errormore("Error code: '%i'\n", GetLastError());
return false;
}
if (!initGLExtensions())
{
error("In Window::renderThreadStartupFunc():\n");
errormore("Failed to initialize OpenGL extensions.\n");
return false;
}
return true;
}
下面是负责启动和关闭线程 B 的代码。它在单独的类中运行，并使用 c++11 的 std::thread 库。
Renderer* Renderer::init(void)
{
/* If the singleton exists already, just return a pointer to it */
if (singleton)
return singleton;
/* Allocate the singleton and check for errors */
singleton = new Renderer();
if (singleton == NULL)
{
fatalerror("In Renderer::init():\n");
fatalmore("Memory allocation failure.\n");
fatalmore("Could not allocate singleton.\n");
_getch();
exit(1);
}
Window::get();
singleton->running = true;
renderThread = new thread(main);
if (renderThread == NULL)
{
fatalerror("In Renderer::init():\n");
fatalmore("Memory allocation failure.\n");
fatalmore("Could not allocate rendering thread.\n");
_getch();
exit(1);
}
Message startup;
startup.type = MT_STARTUP;
singleton->queue.push(startup);
return singleton;
}
void Renderer::clean(void)
{
if (!singleton)
return;
Message shutdown;
shutdown.type = MT_SHUTDOWN;
singleton->queue.push(shutdown);
if (renderThread)
{
renderThread->join();
delete renderThread;
}
}
最佳答案
一些建议:
创建适当的上下文，将临时帮助器上下文作为当前上下文(您的扩展函数指针绑定(bind)到 Windows 中的事件上下文)，即不要释放作为当前上下文的帮助器上下文，也不要释放助手上下文，在创建适当的上下文之前。
在启动线程 B 之前，在适当的上下文和 hdc 上调用 wglMakeCurrent(…)，调用 glFinish()，然后才调用 wglMakeCurrent(NULL, NULL) 并删除临时上下文。对于一些有问题的驱动程序，这是一个肮脏的解决方法。
关于c++ - 第二个线程中的 wglMakeCurrent 失败了吗？，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/21613842/