Fixes, that build is possible with Xlib configuration.

CMakeLists.txt

@@ -15,6 +15,7 @@ if(WIN32)
     add_definitions(-DVK_USE_PLATFORM_WIN32_KHR -DWIN32_LEAN_AND_MEAN)
 else()
     add_definitions(-DVK_USE_PLATFORM_XCB_KHR)
+    add_definitions(-DVK_USE_PLATFORM_XLIB_KHR)
 endif()
 
 set(CMAKE_MODULE_PATH ${CMAKE_MODULE_PATH} "${CMAKE_SOURCE_DIR}/cmake")

cmake/FindX11_XCB.cmake

@@ -0,0 +1,32 @@
+# - Try to find libX11-xcb
+# Once done this will define
+#
+# X11_XCB_FOUND - system has libX11-xcb
+# X11_XCB_LIBRARIES - Link these to use libX11-xcb
+# X11_XCB_INCLUDE_DIR - the libX11-xcb include dir
+# X11_XCB_DEFINITIONS - compiler switches required for using libX11-xcb
+
+# Copyright (c) 2011 Fredrik Höglund <fredrik@kde.org>
+# Copyright (c) 2008 Helio Chissini de Castro, <helio@kde.org>
+# Copyright (c) 2007 Matthias Kretz, <kretz@kde.org>
+#
+# Redistribution and use is allowed according to the terms of the BSD license.
+# For details see the accompanying COPYING-CMAKE-SCRIPTS file.
+
+IF (NOT WIN32)
+  # use pkg-config to get the directories and then use these values
+  # in the FIND_PATH() and FIND_LIBRARY() calls
+  FIND_PACKAGE(PkgConfig)
+  PKG_CHECK_MODULES(PKG_X11_XCB QUIET x11-xcb)
+
+  SET(X11_XCB_DEFINITIONS ${PKG_X11_XCB_CFLAGS})
+
+  FIND_PATH(X11_XCB_INCLUDE_DIR NAMES X11/Xlib-xcb.h HINTS ${PKG_X11_XCB_INCLUDE_DIRS})
+  FIND_LIBRARY(X11_XCB_LIBRARIES NAMES X11-xcb HINTS ${PKG_X11_XCB_LIBRARY_DIRS})
+
+  include(FindPackageHandleStandardArgs)
+  FIND_PACKAGE_HANDLE_STANDARD_ARGS(X11_XCB DEFAULT_MSG X11_XCB_LIBRARIES X11_XCB_INCLUDE_DIR)
+
+  MARK_AS_ADVANCED(X11_XCB_INCLUDE_DIR X11_XCB_LIBRARIES)
+ENDIF (NOT WIN32)
+