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>

4 files changed, 24 insertions, 7 deletions

diff --git a/src/gui/CMakeLists.txt b/src/gui/CMakeLists.txt
index b2520f5e06..4ea528e7ae 100644
--- a/src/gui/CMakeLists.txt
+++ b/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)
diff --git a/src/gui/configure.cmake b/src/gui/configure.cmake
index e5888cc1d7..5e29a60463 100644
--- a/src/gui/configure.cmake
+++ b/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)
-set_package_properties(OpenGL PROPERTIES TYPE OPTIONAL)
+find_package(EGL)
+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
diff --git a/src/platformsupport/eglconvenience/CMakeLists.txt b/src/platformsupport/eglconvenience/CMakeLists.txt
index 2b20a9cb35..af5d277f7a 100644
--- a/src/platformsupport/eglconvenience/CMakeLists.txt
+++ b/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:
diff --git a/src/plugins/platforms/minimalegl/CMakeLists.txt b/src/plugins/platforms/minimalegl/CMakeLists.txt
index a038d07df9..f6d46c55a4 100644
--- a/src/plugins/platforms/minimalegl/CMakeLists.txt
+++ b/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"