能否在Xlib窗口创建完成后再创建GLX上下文？

我希望将Xlib窗口创建与GLX上下文创建拆分为两个独立阶段——先创建好Xlib窗口，再进行OpenGL相关的上下文创建工作。Win32平台下这种分阶段的实现流程比较简单，但我找不到Linux平台下Xlib+OpenGL的相关实现资料。

现有实现参考 #

Linux（Xlib）常规实现方式 #

GLint glxAttribs[] = {
    GLX_RGBA,
    GLX_DOUBLEBUFFER,
    GLX_DEPTH_SIZE,     24,
    GLX_STENCIL_SIZE,   8,
    GLX_RED_SIZE,       8,
    GLX_GREEN_SIZE,     8,
    GLX_BLUE_SIZE,      8,
    GLX_SAMPLE_BUFFERS, 0,
    GLX_SAMPLES,        0,
    None
};


XVisualInfo* visual = glXChooseVisual(display, screenId, glxAttribs);
XSetWindowAttributes windowAttribs;
windowAttribs.border_pixel = BlackPixel(display, screenId);
windowAttribs.background_pixel = WhitePixel(display, screenId);
windowAttribs.override_redirect = True;
windowAttribs.colormap = XCreateColormap(display, RootWindow(display, screenId), visual->visual, AllocNone);
windowAttribs.event_mask = ExposureMask;
window = XCreateWindow(display, RootWindow(display, screenId), 0, 0, 320, 200, 0, visual->depth, InputOutput, visual->visual, CWBackPixel | CWColormap | CWBorderPixel | CWEventMask, &windowAttribs);

Windows平台实现方式 #

const WindowsWindow* pWin32Window = (const WindowsWindow*)pOwnerWindow;

HWND windowHandle = pWin32Window->GetWin32WindowHandle();
HDC windowDeviceContext = pWin32Window->GetWin32WindowDeviceContext();

/*
* Create pixel format
*/
PIXELFORMATDESCRIPTOR pfd = { sizeof(pfd),1 };
memset(&pfd, 0, sizeof(PIXELFORMATDESCRIPTOR));
pfd.nSize = sizeof(PIXELFORMATDESCRIPTOR);
pfd.dwFlags = PFD_DRAW_TO_WINDOW | PFD_SUPPORT_OPENGL | PFD_DOUBLEBUFFER;
pfd.iPixelType = PFD_TYPE_RGBA;
pfd.nVersion = 1;
pfd.cColorBits = OpenGLDeviceUtilsWin32::GetColorBits(desc.SwapchainBufferFormat);
pfd.cAlphaBits = OpenGLDeviceUtilsWin32::GetAlphaBits(desc.SwapchainBufferFormat);
pfd.cDepthBits = OpenGLDeviceUtilsWin32::GetDepthBits(desc.SwapchainDepthStencilBufferFormat);
pfd.cStencilBits = OpenGLDeviceUtilsWin32::GetStencilBits(desc.SwapchainDepthStencilBufferFormat);
pfd.cAuxBuffers = 3;
pfd.iLayerType = PFD_MAIN_PLANE;

const int pixelFormatIndex = ChoosePixelFormat(windowDeviceContext, &pfd);
ASSERT(pixelFormatIndex != 0,"OpenGLDevice","Invalid pixel format");

ASSERT(SetPixelFormat(windowDeviceContext, pixelFormatIndex, &pfd), "OpenGLDevice", "Win32 window rejected the specified pixel format");

HGLRC tempContext = wglCreateContext(windowDeviceContext);
ASSERT(tempContext != NULL, "OpenGLDevice", "Creation of wgl dummy context failed!");

wglMakeCurrent(windowDeviceContext, tempContext);

PFNWGLCREATECONTEXTATTRIBSARBPROC wglCreateContextAttribsARB = NULL;
wglCreateContextAttribsARB = (PFNWGLCREATECONTEXTATTRIBSARBPROC)wglGetProcAddress("wglCreateContextAttribsARB");
ASSERT(wglCreateContextAttribsARB != NULL, "OpenGLDevice", "WGL get proc address failed!");

期望的流程 #

• 创建Xlib窗口
• 检查该窗口是否支持指定GLX属性对应的像素格式
• 使用该像素格式创建GLX上下文

当前常规流程对比 #

• 先通过glXChooseVisual获取符合GLX属性的视觉信息
• 基于该视觉信息创建Xlib窗口
• 再创建GLX上下文

核心疑问 #

是否可以在不提前告知Xlib该窗口将用于OpenGL的情况下创建窗口，后续再完成OpenGL相关的设置流程？

内容的提问来源于stack exchange，提问作者Barış Üçkardeş