Merge pull request #25354 from LaurentBerger:uiname

Add cv::currentUIFramework #25354

issue https://github.com/opencv/opencv/issues/25329

### Pull Request Readiness Checklist

See details at https://github.com/opencv/opencv/wiki/How_to_contribute#making-a-good-pull-request

- [x] I agree to contribute to the project under Apache 2 License.
- [x] To the best of my knowledge, the proposed patch is not based on a code under GPL or another license that is incompatible with OpenCV
- [ ] The PR is proposed to the proper branch
- [x] There is a reference to the original bug report and related work
- [ ] There is accuracy test, performance test and test data in opencv_extra repository, if applicable
      Patch to opencv_extra has the same branch name.
- [x] The feature is well documented and sample code can be built with the project CMake

modules/highgui/src/window.cpp

@@ -1091,6 +1091,33 @@ void cv::imshow(const String& winname, const ogl::Texture2D& _tex)
 #endif
 }
 
+const std::string cv::currentUIFramework()
+{
+    CV_TRACE_FUNCTION();
+
+    // plugin and backend-compatible implementations
+    auto backend = getCurrentUIBackend();
+    if (backend)
+    {
+        return backend->getName();
+    }
+
+    // builtin backends
+#if defined(HAVE_WIN32UI)
+    CV_Assert(false); // backend-compatible
+#elif defined (HAVE_GTK)
+    CV_Assert(false); // backend-compatible
+#elif defined (HAVE_QT)
+    return std::string("QT");
+#elif defined (HAVE_COCOA)
+    return std::string("COCOA");
+#elif defined (HAVE_WAYLAND)
+    return std::string("WAYLAND");
+#else
+    return std::string();
+#endif
+}
+
 // Without OpenGL
 
 #ifndef HAVE_OPENGL