Why can't create xcb surface?

[sunbearc22]

@realitix I noticed an issue with creating a xcb surface. My function to create such a surface is given below. However, vkGetInstanceProcAddr gives a ProcedureNotFoundError.

I can create a xlib surface. Also, previously I had tested the same code to make a xcb surface a year ago and that worked. Can you point me the cause of the issue as I can't figure it out? I have checked for the presence of vkCreateXcbSurfaceKHR in _vulkan.py and vulkan.cdef.h and found it mentioned there. The libx11 packages on my system are shown below too. So what gives?

    def setSurface(self):

        info = self.window.info.info
        
        def create_surface(name, surface_createInfo):
            f = vkGetInstanceProcAddr(self.instance, name)
            return f(self.instance, surface_createInfo, None)
        
        def _surface_xlib():
            surface_createInfo = VkXlibSurfaceCreateInfoKHR(
                sType = VK_STRUCTURE_TYPE_XLIB_SURFACE_CREATE_INFO_KHR,
                flags = 0,
                dpy    = info.x11.display,
                window = info.x11.window)
            return create_surface('vkCreateXlibSurfaceKHR', surface_createInfo)

        def _surface_xcb():
            surface_createInfo = VkXcbSurfaceCreateInfoKHR(
                sType = VK_STRUCTURE_TYPE_XCB_SURFACE_CREATE_INFO_KHR,
                flags = 0,
                connection = info.x11.display,
                window     = info.x11.window)
            return create_surface('vkCreateXcbSurfaceKHR', surface_createInfo)

        surface_mapping = { 'VK_KHR_xlib_surface': _surface_xlib,
                            'VK_KHR_xcb_surface': _surface_xcb,
                            }

        err = '- fail to create Vulkan Surface: '
        try:
            self.surface = surface_mapping[self.window.vulkan_surface_ext]()
        except VkError:
            logging.error(err)
            self.cleanup()

  File "~/Vulkan/MyProject/triangle_example/triangle11.py", line 160, in surface_xlib
    vkCreateXlibSurfaceKHR = vkGetInstanceProcAddr(instance, "vkCreateXlibSurfaceKHR")
  File "~/.local/lib/python3.5/site-packages/vulkan/_vulkan.py", line 6856, in vkGetInstanceProcAddr
    raise ProcedureNotFoundError()
vulkan._vulkan.ProcedureNotFoundError

$ dpkg -l | grep libx11
ii  libx11-6:amd64                              2:1.6.3-1ubuntu2                                 amd64        X11 client-side library
ii  libx11-data                                 2:1.6.3-1ubuntu2                                 all          X11 client-side library
ii  libx11-dev:amd64                            2:1.6.3-1ubuntu2                                 amd64        X11 client-side library (development headers)
ii  libx11-doc                                  2:1.6.3-1ubuntu2                                 all          X11 client-side library (development documentation)
ii  libx11-protocol-perl                        0.56-7                                           all          Perl module for the X Window System Protocol, version 11
ii  libx11-xcb-dev:amd64                        2:1.6.3-1ubuntu2                                 amd64        Xlib/XCB interface library (development headers)
ii  libx11-xcb1:amd64                           2:1.6.3-1ubuntu2                                 amd64        Xlib/XCB interface library

[sunbearc22]

Pardon me. The issue was caused by my code and I have resolve it. Able to create xcb surface.