Fix OpenGL vs. GLESv2 linkage, attempt number three

We introduced WrapOpenGL to link against either desktop GL or GLESv2
depending on the GL feature in QtGui. This works "fine", with two
caveats:

    (1) find_package(WrapOpenGL) must be called after
    find_package(Qt5Gui) in order for the feature check in
    FindWrapOpenGL.cmake to work. That's error prone.

    (2) More and more places are popping up, in particular examples,
    where GL linkage is required due to inline functions in Qt that
    forward to GL functions - such as on Android.

    This in particular explains the qmake behavior of making the GL
    linkage (desktop _or_ GLES) a public dependency of QtGui, so only
    Gui linkage is required.

Those two aspects combined are the nail in the coffin of FindWrapOpenGL
and it would seem much easier to simply make the Desktop GL vs. GLES
decision once in Gui's CMakeLists.txt and let Qt5GuiDependencies.cmake
propagate this well. This allows us to get rid of plenty of special
cases as well.

Change-Id: I3a7e8af49537ce5f215f24470e075a4ae9aeb944
Reviewed-by: Alexandru Croitor <alexandru.croitor@qt.io>

cmake/FindWrapOpenGL.cmake

@@ -1,20 +0,0 @@
-
-# Logic derived from mkspecs/features/unix/opengl.prf: prefer GLESv2 over GL
-
-if(TARGET WrapOpenGL)
-    set(WrapOpenGL_FOUND ON)
-    return()
-endif()
-
-add_library(WrapOpenGL INTERFACE IMPORTED)
-
-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()
-set(WrapOpenGL_FOUND ON)
-
-set_property(TARGET WrapOpenGL PROPERTY IMPORTED_GLOBAL TRUE)

examples/widgets/graphicsview/boxes/CMakeLists.txt

@@ -1,6 +1,5 @@
 # Generated from boxes.pro.
 
-qt_find_package(WrapOpenGL PROVIDED_TARGETS WrapOpenGL) # special case
 #####################################################################
 ## boxes Binary:
 #####################################################################
@@ -22,7 +21,6 @@ add_qt_executable(boxes
     LIBRARIES
         Qt::OpenGL
         Qt::Widgets
-        WrapOpenGL
 )
 
 # Resources:

src/gui/CMakeLists.txt

@@ -336,12 +336,20 @@ extend_target(Gui CONDITION QT_FEATURE_standarditemmodel
 
 # special case begin
 # With qmake, gui's opengl.pri used CONFIG += opengl, where opengl.prf
-# acted like WrapOpenGL: direct linkage against either libGLESv2 or
+# used direct public linkage against either libGLESv2 or libGL, depending
-# libGL, depending on the opengl _feature_. This is done by hand now
+# on the opengl _feature_. This is done by hand now here (where the
-# here (where the feature is available).
+# feature is available).
 # DO NOT MOVE THIS TO THE BEGINNING OF THE FILE, the feature variables are not
 # available until the add_qt_module call.
-qt_find_package(WrapOpenGL PROVIDED_TARGETS WrapOpenGL)
+if(QT_FEATURE_opengl)
+    if(QT_FEATURE_opengles2)
+        find_package(GLESv2)
+        target_link_libraries(Gui PUBLIC GLESv2::GLESv2)
+    else()
+        find_package(OpenGL)
+        target_link_libraries(Gui PUBLIC OpenGL::GL)
+    endif()
+endif()
 # special case end
 
 extend_target(Gui CONDITION QT_FEATURE_opengl
@@ -376,20 +384,8 @@ extend_target(Gui CONDITION QT_FEATURE_opengl
         opengl/qopenglversionfunctions.cpp opengl/qopenglversionfunctions.h
         opengl/qopenglversionfunctionsfactory.cpp opengl/qopenglversionfunctionsfactory_p.h
         opengl/qopenglvertexarrayobject.cpp opengl/qopenglvertexarrayobject.h
-    LIBRARIES # special case
-        WrapOpenGL # special case
 )
 
-# special case begin
-# qopenglfunctions.h on Android does not use the function
-# table indirection for calls but calls ::glFoo in inline functions
-# directly. That means the GL library is a public dependency.
-extend_target(Gui CONDITION QT_FEATURE_opengl AND ANDROID
-    PUBLIC_LIBRARIES
-        WrapOpenGL
-)
-# special case end
-
 #### Keys ignored in scope 2:.:.:gui.pro:QT_FEATURE_opengl:
 # MODULE_CONFIG = "opengl"
 

src/opengl/CMakeLists.txt

@@ -30,7 +30,6 @@ add_qt_module(OpenGL
         Qt::CorePrivate
         Qt::GuiPrivate
         Qt::WidgetsPrivate
-        WrapOpenGL # special case
     PUBLIC_LIBRARIES
         Qt::Core
         Qt::Gui

src/platformsupport/glxconvenience/CMakeLists.txt

@@ -1,7 +1,6 @@
 # Generated from glxconvenience.pro.
 
 qt_find_package(X11) # special case
-qt_find_package(WrapOpenGL PROVIDED_TARGETS WrapOpenGL) # special case
 
 #####################################################################
 ## GlxSupport Module:
@@ -14,7 +13,6 @@ add_qt_module(GlxSupport
     DEFINES
         QT_NO_CAST_FROM_ASCII
     LIBRARIES
-        WrapOpenGL # special case
         Qt::CorePrivate
         Qt::GuiPrivate
         X11::X11 # special case

src/plugins/platforms/cocoa/CMakeLists.txt

@@ -2,7 +2,6 @@
 
 # special case:
 qt_find_package(Cups PROVIDED_TARGETS Cups::Cups)
-qt_find_package(WrapOpenGL PROVIDED_TARGETS WrapOpenGL)
 
 #####################################################################
 ## qcocoa Plugin:
@@ -92,8 +91,6 @@ add_qt_resource(qcocoa "qcocoaresources" PREFIX "/qt-project.org/mac/cursors" FI
 extend_target(qcocoa CONDITION QT_FEATURE_opengl # special case
     SOURCES
         qcocoaglcontext.h qcocoaglcontext.mm
-    LIBRARIES
-        WrapOpenGL # special case
 )
 
 extend_target(qcocoa CONDITION QT_FEATURE_vulkan

src/plugins/platforms/eglfs/CMakeLists.txt

@@ -1,5 +1,4 @@
 qt_find_package(EGL) # special case
-qt_find_package(WrapOpenGL PROVIDED_TARGETS WrapOpenGL) # special case
 
 #####################################################################
 ## EglFSDeviceIntegration Module:
@@ -30,7 +29,6 @@ add_qt_module(EglFSDeviceIntegration
         Qt::ServiceSupportPrivate
         Qt::ThemeSupportPrivate
         EGL::EGL # special case
-        WrapOpenGL # special case
 )
 
 #### Keys ignored in scope 2:.:./eglfsdeviceintegration.pro:<NONE>:

src/plugins/platforms/minimalegl/CMakeLists.txt

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

tests/CMakeLists.txt

@@ -9,7 +9,6 @@ if(NOT TARGET Qt::Test)
     # Find a few packages that are usually found in configure.cmake,
     # because a few tests link directly against those libraries.
     qt_find_package(WrapDBus1 PROVIDED_TARGETS dbus-1)
-    qt_find_package(WrapOpenGL PROVIDED_TARGETS WrapOpenGL)
 endif()
 # special case end