Improve CMake checks for the OpenGL availability

Issue #2868

CMakeLists.txt

@@ -118,11 +118,11 @@ OCV_OPTION(WITH_CUFFT          "Include NVidia Cuda Fast Fourier Transform (FFT)
 OCV_OPTION(WITH_CUBLAS         "Include NVidia Cuda Basic Linear Algebra Subprograms (BLAS) library support" OFF IF (CMAKE_VERSION VERSION_GREATER "2.8" AND NOT ANDROID AND NOT IOS) )
 OCV_OPTION(WITH_NVCUVID        "Include NVidia Video Decoding library support"                               OFF IF (CMAKE_VERSION VERSION_GREATER "2.8" AND NOT ANDROID AND NOT IOS AND NOT APPLE) )
 OCV_OPTION(WITH_EIGEN          "Include Eigen2/Eigen3 support"               ON)
-OCV_OPTION(WITH_VFW            "Include Video for Windows support"           ON   IF (WIN32))
+OCV_OPTION(WITH_VFW            "Include Video for Windows support"           ON   IF WIN32 )
 OCV_OPTION(WITH_FFMPEG         "Include FFMPEG support"                      ON   IF (NOT ANDROID AND NOT IOS))
 OCV_OPTION(WITH_GSTREAMER      "Include Gstreamer support"                   ON   IF (UNIX AND NOT APPLE AND NOT ANDROID) )
 OCV_OPTION(WITH_GTK            "Include GTK support"                         ON   IF (UNIX AND NOT APPLE AND NOT ANDROID) )
-OCV_OPTION(WITH_IMAGEIO        "ImageIO support for OS X"                    OFF  IF APPLE)
+OCV_OPTION(WITH_IMAGEIO        "ImageIO support for OS X"                    OFF  IF APPLE )
 OCV_OPTION(WITH_IPP            "Include Intel IPP support"                   OFF  IF (MSVC OR X86 OR X86_64) )
 OCV_OPTION(WITH_JASPER         "Include JPEG2K support"                      ON   IF (NOT IOS) )
 OCV_OPTION(WITH_JPEG           "Include JPEG support"                        ON)
@@ -133,7 +133,7 @@ OCV_OPTION(WITH_PNG            "Include PNG support"                         ON)
 OCV_OPTION(WITH_PVAPI          "Include Prosilica GigE support"              ON   IF (NOT ANDROID AND NOT IOS) )
 OCV_OPTION(WITH_GIGEAPI        "Include Smartek GigE support"                ON   IF (NOT ANDROID AND NOT IOS) )
 OCV_OPTION(WITH_QT             "Build with Qt Backend support"               OFF  IF (NOT ANDROID AND NOT IOS) )
-OCV_OPTION(WITH_WIN32UI        "Build with Win32 UI Backend support"         ON   IF (WIN32) )
+OCV_OPTION(WITH_WIN32UI        "Build with Win32 UI Backend support"         ON   IF WIN32 )
 OCV_OPTION(WITH_QUICKTIME      "Use QuickTime for Video I/O insted of QTKit" OFF  IF APPLE )
 OCV_OPTION(WITH_TBB            "Include Intel TBB support"                   OFF  IF (NOT IOS) )
 OCV_OPTION(WITH_CSTRIPES       "Include C= support"                          OFF  IF WIN32 )

cmake/OpenCVFindLibsGUI.cmake

@@ -35,7 +35,7 @@ endif()
 # --- OpenGl ---
 ocv_clear_vars(HAVE_OPENGL HAVE_QT_OPENGL)
 if(WITH_OPENGL)
-  if(WIN32 OR QT_QTOPENGL_FOUND OR HAVE_GTKGLEXT)
+  if(WITH_WIN32UI OR (HAVE_QT AND QT_QTOPENGL_FOUND) OR HAVE_GTKGLEXT)
     find_package (OpenGL QUIET)
     if(OPENGL_FOUND)
       set(HAVE_OPENGL TRUE)