Fix Desktop GL/EGL/GLESv2 linkage

This change fixes a few things in one go:

  * cmake's FindOpenGL cannot be used reliably to detect EGL. So use a
    custom module for that.
  * Added a custom module for GLESv2 detection, as cmake's FindOpenGL
    does not support that.
  * Map CONFIG += opengl to a WrapOpenGL target, which links against
    either GLESv2 or libGL - just like mkspecs/features/*/opengl.prf
  * cmake's FindOpenGL remains in use solely to detect the availability
    of desktop gl.

Change-Id: I9315e5ad1fd88e1b7dc7e920053e98fb51fea7fc
Reviewed-by: Volker Krause <volker.krause@kdab.com>

cmake/FindEGL.cmake

@@ -0,0 +1,32 @@
+include(CheckCXXSourceCompiles)
+include(CMakePushCheckState)
+
+find_library(EGL_LIBRARY NAMES EGL)
+find_path(EGL_INCLUDE_DIR NAMES "EGL/egl.h" DOC "The EGL include path")
+
+cmake_push_check_state(RESET)
+list(APPEND CMAKE_REQUIRED_LIBRARIES "${EGL_LIBRARY}")
+list(APPEND CMAKE_REQUIRED_INCLUDES "${EGL_INCLUDE_DIR}")
+
+check_cxx_source_compiles("
+#include <EGL/egl.h>
+
+int main(int argc, char *argv[]) {
+    EGLint x = 0; EGLDisplay dpy = 0; EGLContext ctx = 0;
+    eglDestroyContext(dpy, ctx);
+}" HAVE_EGL)
+
+cmake_pop_check_state()
+
+
+include(FindPackageHandleStandardArgs)
+find_package_handle_standard_args(EGL DEFAULT_MSG EGL_INCLUDE_DIR EGL_LIBRARY HAVE_EGL)
+
+mark_as_advanced(EGL_INCLUDE_DIR EGL_LIBRARY HAVE_EGL)
+
+if(EGL_FOUND AND NOT TARGET EGL::EGL)
+    add_library(EGL::EGL UNKNOWN IMPORTED)
+    set_target_properties(EGL::EGL PROPERTIES
+        IMPORTED_LOCATION "${EGL_LIBRARY}"
+        INTERFACE_INCLUDE_DIRECTORIES "${EGL_INCLUDE_DIR}")
+endif()

cmake/FindGLESv2.cmake

@@ -0,0 +1,40 @@
+include(CheckCXXSourceCompiles)
+
+find_library(GLESv2_LIBRARY NAMES GLESv2)
+find_path(GLESv2_INCLUDE_DIR NAMES "GLES2/gl2.h" DOC "The OpenGLES 2 include path")
+
+set(_libraries "${CMAKE_REQUIRED_LIBRARIES}")
+list(APPEND CMAKE_REQUIRED_LIBRARIES "${GLESv2_LIBRARY}")
+set(_includes "${CMAKE_REQUIRED_INCLUDES}")
+list(APPEND CMAKE_REQUIRED_INCLUDES "${GLESv2_INCLUDE_DIR}")
+
+check_cxx_source_compiles("
+#ifdef __APPLE__
+#  include <OpenGLES/ES2/gl.h>
+#else
+#  define GL_GLEXT_PROTOTYPES
+#  include <GLES2/gl2.h>
+#endif
+
+int main(int argc, char *argv[]) {
+    glUniform1f(1, GLfloat(1.0));
+    glClear(GL_COLOR_BUFFER_BIT);
+}" HAVE_GLESv2)
+
+set(CMAKE_REQUIRED_LIBRARY "${_libraries}")
+unset(_libraries)
+set(CMAKE_REQUIRED_INCLUDES "${_includes}")
+unset(_includes)
+
+
+include(FindPackageHandleStandardArgs)
+find_package_handle_standard_args(GLESv2 DEFAULT_MSG GLESv2_INCLUDE_DIR GLESv2_LIBRARY HAVE_GLESv2)
+
+mark_as_advanced(GLESv2_INCLUDE_DIR GLESv2_LIBRARY HAVE_GLESv2)
+
+if(GLESv2_FOUND AND NOT TARGET GLESv2::GLESv2)
+    add_library(GLESv2::GLESv2 UNKNOWN IMPORTED)
+    set_target_properties(GLESv2::GLESv2 PROPERTIES
+        IMPORTED_LOCATION "${GLESv2_LIBRARY}"
+        INTERFACE_INCLUDE_DIRECTORIES "${GLESv2_INCLUDE_DIR}")
+endif()

cmake/FindWrapOpenGL.cmake

@@ -0,0 +1,16 @@
+
+# Logic derived from mkspecs/features/unix/opengl.prf: prefer GLESv2 over GL
+
+if(TARGET WrapOpenGL)
+    return()
+endif()
+
+add_library(WrapOpenGL INTERFACE)
+
+if(QT_FEATURE_opengles2)
+    find_package(GLESv2)
+    target_link_libraries(WrapOpenGL INTERFACE GLESv2::GLESv2)
+else()
+    find_package(OpenGL)
+    target_link_libraries(WrapOpenGL INTERFACE OpenGL::GL)
+endif()

src/gui/CMakeLists.txt

@@ -317,6 +317,12 @@ extend_target(Gui CONDITION TEST_architecture STREQUAL arm64 AND NOT APPLE_UIKIT
     DEFINES ENABLE_PIXMAN_DRAWHELPERS
 )
 
+# With qmake, gui's opengl.pri used CONFIG += opengl, where opengl.prf
+# acted like WrapOpenGL: direct linkage against either libGLESv2 or
+# libGL, depending in the opengl _feature_. This is done by hand now
+# here (where the feature is available).
+find_package(WrapOpenGL)
+
 extend_target(Gui CONDITION QT_FEATURE_opengl
     SOURCES
         opengl/qopengl.cpp opengl/qopengl.h opengl/qopengl_p.h
@@ -347,7 +353,7 @@ extend_target(Gui CONDITION QT_FEATURE_opengl
         opengl/qopenglversionfunctionsfactory.cpp opengl/qopenglversionfunctionsfactory_p.h
         opengl/qopenglvertexarrayobject.cpp opengl/qopenglvertexarrayobject.h
     LIBRARIES
-        OpenGL::GL
+        WrapOpenGL
 )
 
 extend_target(Gui CONDITION (QT_FEATURE_opengl) AND (NOT QT_FEATURE_opengles2)

src/gui/configure.cmake

@@ -38,8 +38,8 @@ find_package(ATSPI2)
 set_package_properties(ATSPI2 PROPERTIES TYPE OPTIONAL)
 find_package(Libdrm)
 set_package_properties(Libdrm PROPERTIES TYPE OPTIONAL)
-find_package(OpenGL)
+find_package(EGL)
-set_package_properties(OpenGL PROPERTIES TYPE OPTIONAL)
+set_package_properties(EGL PROPERTIES TYPE OPTIONAL)
 find_package(Freetype)
 set_package_properties(Freetype PROPERTIES TYPE OPTIONAL)
 find_package(Fontconfig)
@@ -56,6 +56,10 @@ find_package(PNG)
 set_package_properties(PNG PROPERTIES TYPE OPTIONAL)
 find_package(Mtdev)
 set_package_properties(Mtdev PROPERTIES TYPE OPTIONAL)
+find_package(OpenGL)
+set_package_properties(OpenGL PROPERTIES TYPE OPTIONAL)
+find_package(GLESv2)
+set_package_properties(GLESv2 PROPERTIES TYPE OPTIONAL)
 find_package(Tslib)
 set_package_properties(Tslib PROPERTIES TYPE OPTIONAL)
 find_package(Vulkan)
@@ -537,7 +541,7 @@ qt_feature("mtdev" PRIVATE
 )
 qt_feature("opengles2" PUBLIC
     LABEL "OpenGL ES 2.0"
-    CONDITION WIN32 OR ( NOT APPLE_WATCHOS AND NOT QT_FEATURE_opengl_desktop AND libs.opengl_es2 ) OR FIXME
+    CONDITION WIN32 OR ( NOT APPLE_WATCHOS AND NOT QT_FEATURE_opengl_desktop AND GLESv2_FOUND )
     ENABLE INPUT_opengl STREQUAL 'es2'
     DISABLE INPUT_opengl STREQUAL 'desktop' OR INPUT_opengl STREQUAL 'dynamic' OR INPUT_opengl STREQUAL 'no'
 )
@@ -586,7 +590,7 @@ qt_feature("openvg" PUBLIC
 )
 qt_feature("egl" PUBLIC PRIVATE
     LABEL "EGL"
-    CONDITION ( QT_FEATURE_opengl OR QT_FEATURE_openvg ) AND ( QT_FEATURE_angle OR OpenGL_EGL_FOUND )
+    CONDITION ( QT_FEATURE_opengl OR QT_FEATURE_openvg ) AND ( QT_FEATURE_angle OR EGL_FOUND )
 )
 qt_feature_definition("egl" "QT_NO_EGL" NEGATE VALUE "1")
 qt_feature("egl_x11" PRIVATE

src/platformsupport/eglconvenience/CMakeLists.txt

@@ -1,6 +1,6 @@
 # Generated from eglconvenience.pro.
 
-find_package(OpenGL)
+find_package(EGL)
 
 #####################################################################
 ## EglSupport Module:
@@ -18,8 +18,12 @@ add_qt_module(EglSupport
     LIBRARIES
         Qt::CorePrivate
         Qt::GuiPrivate
-        OpenGL::EGL
+        EGL::EGL
         ${CMAKE_DL_LIBS}
+    # CONFIG = "static" "internal_module" "egl"
+    # MODULE = "egl_support"
+    # PRECOMPILED_HEADER = "../../corelib/global/qt_pch.h"
+    # _LOADED = "qt_module"
 )
 
 ## Scopes:

src/plugins/platforms/minimalegl/CMakeLists.txt

@@ -1,5 +1,7 @@
 # Generated from minimalegl.pro.
 
+find_package(FindWrapOpenGL)
+
 #####################################################################
 ## qminimalegl Plugin:
 #####################################################################
@@ -19,6 +21,7 @@ add_qt_plugin(qminimalegl
         Qt::EventDispatcherSupportPrivate
         Qt::FontDatabaseSupportPrivate
         Qt::EglSupportPrivate
+        WrapOpenGL
     # CONFIG = "egl"
     # OTHER_FILES = "minimalegl.json"
     # PLUGIN_CLASS_NAME = "QMinimalEglIntegrationPlugin"

util/cmake/configurejson2cmake.py

@@ -52,7 +52,7 @@ def map_library(lib: str) -> Union[str, LibraryMapping, List[str]]:
        'cups': 'Cups',
        'double-conversion': 'WrapDoubleConversion',
        'drm': 'Libdrm',
-       'egl': LibraryMapping(package="OpenGL", resultVariable="OpenGL_EGL"),
+       'egl': 'EGL',
        'fontconfig': LibraryMapping(package='Fontconfig', resultVariable="FONTCONFIG"),
        'freetype': 'Freetype',
        'gbm': 'gbm',
@@ -101,6 +101,7 @@ def map_library(lib: str) -> Union[str, LibraryMapping, List[str]]:
        'xrender': LibraryMapping(package="XCB", resultVariable="XCB_RENDER"),
        'zlib': 'ZLIB',
        'zstd': 'ZSTD',
+       'opengl_es2': 'GLESv2',
     }  # type: Dict[str, Union[str, List[str], LibraryMapping]]
     if lib not in libmap:
         raise Exception('    XXXX Unknown library "{}".'.format(lib))