eglconvenience: Ensure we can query all GL functions

Follow changed from qtbase 5e9a5246fb688a33ff27bed010226595f579f23d
to reduce or remove OS dependant code paths.

cmake/FindLibdl.cmake

@@ -0,0 +1,102 @@
+#.rst:
+# FindLibdl
+# ---------
+#
+# Try to find libdl on a Unix system.
+#
+# This will define the following variables:
+#
+# ``Libdl_FOUND``
+#     True if (the requested version of) libdl is available
+# ``Libdl_LIBRARIES``
+#     This can be passed to target_link_libraries() instead of the ``Libdl::Libdl``
+#     target
+# ``Libdl_INCLUDE_DIRS``
+#     This should be passed to target_include_directories() if the target is not
+#     used for linking
+#
+# If ``Libdl_FOUND`` is TRUE, it will also define the following imported target:
+#
+# ``Libdl::Libdl``
+#     The libdl library
+#
+# In general we recommend using the imported target, as it is easier to use.
+# Bear in mind, however, that if the target is in the link interface of an
+# exported library, it must be made available by the package config file.
+
+#=============================================================================
+# Copyright 2016 Pier Luigi Fiorini <[email protected]>
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions
+# are met:
+#
+# 1. Redistributions of source code must retain the copyright
+#    notice, this list of conditions and the following disclaimer.
+# 2. Redistributions in binary form must reproduce the copyright
+#    notice, this list of conditions and the following disclaimer in the
+#    documentation and/or other materials provided with the distribution.
+# 3. The name of the author may not be used to endorse or promote products
+#    derived from this software without specific prior written permission.
+#
+# THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
+# IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
+# OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
+# IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
+# INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
+# NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+# THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
+# THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+#=============================================================================
+
+if(CMAKE_VERSION VERSION_LESS 2.8.12)
+    message(FATAL_ERROR "CMake 2.8.12 is required by FindLibdl.cmake")
+endif()
+if(CMAKE_MINIMUM_REQUIRED_VERSION VERSION_LESS 2.8.12)
+    message(AUTHOR_WARNING "Your project should require at least CMake 2.8.12 to use FindLibdl.cmake")
+endif()
+
+if(UNIX)
+    find_path(Libdl_INCLUDE_DIR
+        NAMES
+            dlfcn.h
+    )
+    find_library(Libdl_LIBRARY
+        NAMES
+            dl libdl ltdl libltdl
+    )
+
+    include(FindPackageHandleStandardArgs)
+    find_package_handle_standard_args(Libdl
+        FOUND_VAR
+            Libdl_FOUND
+        REQUIRED_VARS
+            Libdl_LIBRARY
+            Libdl_INCLUDE_DIR
+    )
+
+    if(Libdl_FOUND AND NOT TARGET Libdl::Libdl)
+        add_library(Libdl::Libdl UNKNOWN IMPORTED)
+        set_target_properties(Libdl::Libdl PROPERTIES
+            IMPORTED_LOCATION "${Libdl_LIBRARY}"
+            INTERFACE_COMPILE_OPTIONS "${Libdl_DEFINITIONS}"
+            INTERFACE_INCLUDE_DIRECTORIES "${Libdl_INCLUDE_DIR}"
+        )
+    endif()
+
+    mark_as_advanced(Libdl_LIBRARY Libdl_INCLUDE_DIR)
+
+    # compatibility variables
+    set(Libdl_LIBRARIES ${Libdl_LIBRARY})
+    set(Libdl_INCLUDE_DIRS ${Libdl_INCLUDE_DIR})
+else()
+    message(STATUS "FindLibdl.cmake can find libdl only on UNIX systems.")
+    set(Libdl_FOUND FALSE)
+endif()
+
+include(FeatureSummary)
+set_package_properties(Libdl PROPERTIES
+    DESCRIPTION "Programming interface to dynamic linking loader."
+)

src/platform/CMakeLists.txt

@@ -15,6 +15,12 @@ set_package_properties(Libinput PROPERTIES
 # gio
 pkg_check_modules(gio gio-2.0 REQUIRED)
 
+# libdl
+find_package(Libdl REQUIRED)
+set_package_properties(Libdl PROPERTIES
+    TYPE REQUIRED
+    PURPOSE "Required to load GL functions")
+
 # Qt5PlatformSupport
 find_package(Qt5PlatformSupport REQUIRED)
 find_package(Freetype REQUIRED)
@@ -77,6 +83,7 @@ target_include_directories(GreenIslandPlatform
         ${CMAKE_BINARY_DIR}/headers/GreenIsland
         ${Qt5Core_PRIVATE_INCLUDE_DIRS}
         ${Qt5Gui_PRIVATE_INCLUDE_DIRS}
+        ${Libdl_INCLUDE_DIR}
 )
 
 target_link_libraries(GreenIslandPlatform
@@ -90,6 +97,7 @@ target_link_libraries(GreenIslandPlatform
         ${gio_LIBRARIES}
     PRIVATE
         Libinput::Libinput
+        Libdl::Libdl
         ${FONTCONFIG_LIBRARIES}
         ${FREETYPE_LIBRARIES}
         Qt5PlatformSupport::Qt5PlatformSupport

src/platform/eglconvenience/eglplatformcontext.cpp

@@ -45,6 +45,10 @@
 #include <QtCore/private/qjnihelpers_p.h>
 #endif
 
+#ifndef Q_OS_WIN
+#include <dlfcn.h>
+#endif
+
 #include "logging.h"
 #include "eglplatformcontext.h"
 #include "eglconvenience.h"
@@ -446,7 +450,12 @@ void EGLPlatformContext::swapBuffers(QPlatformSurface *surface)
 QFunctionPointer EGLPlatformContext::getProcAddress(const char *procName)
 {
     eglBindAPI(m_api);
-    return eglGetProcAddress(procName);
+    QFunctionPointer proc = (QFunctionPointer) eglGetProcAddress(procName);
+#ifndef Q_OS_WIN
+    if (!proc)
+        proc = (QFunctionPointer) dlsym(RTLD_DEFAULT, procName);
+#endif
+    return proc;
 }
 #else
 void (*EGLPlatformContext::getProcAddress(const QByteArray &procName)) ()