Merge pull request #15282 from andrey-golubev:rename_argkind_opaque

* G-API: rename ArgKind OPAQUE to GOPAQUE

Rename ArgKind value to GOPAQUE to fix conflict in the
user code when wingdi.h is included: it defines OPAQUE
macro that (for some reason) is chosen instead of ArgKind
value

* Add compatibility with existing API

* Renamed GOPAQUE to OPAQUE_VAL

modules/gapi/include/opencv2/gapi/garg.hpp

@@ -76,7 +76,7 @@ public:
         return util::unsafe_any_cast<typename std::remove_reference<T>::type>(value);
     }
 
-    detail::ArgKind kind = detail::ArgKind::OPAQUE;
+    detail::ArgKind kind = detail::ArgKind::OPAQUE_VAL;
 
 protected:
     util::any value;

modules/gapi/include/opencv2/gapi/gtype_traits.hpp

@@ -26,7 +26,11 @@ namespace detail
     // a double dispatch
     enum class ArgKind: int
     {
-        OPAQUE,       // Unknown, generic, opaque-to-GAPI data type - STATIC
+        OPAQUE_VAL,   // Unknown, generic, opaque-to-GAPI data type - STATIC
+                      // Note: OPAQUE is sometimes defined in Win sys headers
+#if !defined(OPAQUE) && !defined(CV_DOXYGEN)
+        OPAQUE = OPAQUE_VAL,  // deprecated value used for compatibility, use OPAQUE_VAL instead
+#endif
         GOBJREF,      // <internal> reference to object
         GMAT,         // a cv::GMat
         GMATP,        // a cv::GMatP
@@ -41,7 +45,7 @@ namespace detail
     template<typename T> struct GTypeTraits;
     template<typename T> struct GTypeTraits
     {
-        static constexpr const ArgKind kind = ArgKind::OPAQUE;
+        static constexpr const ArgKind kind = ArgKind::OPAQUE_VAL;
     };
     template<>           struct GTypeTraits<cv::GMat>
     {

modules/gapi/test/internal/gapi_int_garg_test.cpp

@@ -39,14 +39,14 @@ using GArg_Test_Types = ::testing::Types
    , Expected<cv::GArray<cv::Rect>,     cv::detail::ArgKind::GARRAY>
 
  // Built-in types
-   , Expected<int,                      cv::detail::ArgKind::OPAQUE>
-   , Expected<float,                    cv::detail::ArgKind::OPAQUE>
-   , Expected<int*,                     cv::detail::ArgKind::OPAQUE>
-   , Expected<cv::Point,                cv::detail::ArgKind::OPAQUE>
-   , Expected<std::string,              cv::detail::ArgKind::OPAQUE>
-   , Expected<cv::Mat,                  cv::detail::ArgKind::OPAQUE>
-   , Expected<std::vector<int>,         cv::detail::ArgKind::OPAQUE>
-   , Expected<std::vector<cv::Point>,   cv::detail::ArgKind::OPAQUE>
+   , Expected<int,                      cv::detail::ArgKind::OPAQUE_VAL>
+   , Expected<float,                    cv::detail::ArgKind::OPAQUE_VAL>
+   , Expected<int*,                     cv::detail::ArgKind::OPAQUE_VAL>
+   , Expected<cv::Point,                cv::detail::ArgKind::OPAQUE_VAL>
+   , Expected<std::string,              cv::detail::ArgKind::OPAQUE_VAL>
+   , Expected<cv::Mat,                  cv::detail::ArgKind::OPAQUE_VAL>
+   , Expected<std::vector<int>,         cv::detail::ArgKind::OPAQUE_VAL>
+   , Expected<std::vector<cv::Point>,   cv::detail::ArgKind::OPAQUE_VAL>
    >;
 
 TYPED_TEST_CASE(GArgKind, GArg_Test_Types);