0004-fix-detection-for-protobuf-23.x.patch

From 0913b73bff8085886dc3f554f552a46e063986d4 Mon Sep 17 00:00:00 2001
From: Silvio Traversaro <silvio@traversaro.it>
Date: Sun, 4 Jun 2023 19:21:33 +0200
Subject: [PATCH 4/4] fix detection for protobuf 23.x

---
 cmake/OpenCVFindProtobuf.cmake | 18 +++++++++++++++++-
 1 file changed, 17 insertions(+), 1 deletion(-)

diff --git a/cmake/OpenCVFindProtobuf.cmake b/cmake/OpenCVFindProtobuf.cmake
index 8835347d1d..6c5b04db2d 100644
--- a/cmake/OpenCVFindProtobuf.cmake
+++ b/cmake/OpenCVFindProtobuf.cmake
@@ -31,7 +31,23 @@ if(BUILD_PROTOBUF)
   set(HAVE_PROTOBUF TRUE)
 else()
   unset(Protobuf_VERSION CACHE)
-  find_package(Protobuf QUIET)
+  # First look for protobuf-config.cmake, and only later use
+  # FindProtobuf.cmake shipped with CMake, for compatibility
+  # with protobuf >= 22
+  set(protobuf_MODULE_COMPATIBLE TRUE CACHE INTERNAL "")
+  find_package(Protobuf CONFIG QUIET)
+  if(Protobuf_FOUND)
+    # if protobuf-config.cmake is used, we need to explicitly
+    # support the case in which we are cross-compiling and we want
+    # to explicitly specify via CMake command line the protoc to use
+    if(Protobuf_PROTOC_EXECUTABLE)
+      set_target_properties(protobuf::protoc PROPERTIES
+        IMPORTED_LOCATION_RELEASE "${Protobuf_PROTOC_EXECUTABLE}"
+      )
+    endif()
+  else()
+    find_package(Protobuf QUIET)
+  endif()
 
   # Backwards compatibility
   # Define camel case versions of input variables