From 9415560250e0aa1dc1850a6947a5d05719192536 Mon Sep 17 00:00:00 2001
From: Maksim Shabunin <maksim.shabunin@gmail.com>
Date: Tue, 21 Apr 2020 15:17:45 +0300
Subject: [PATCH] videoio: load debug versions of plug-ins in debug builds

---
 modules/videoio/CMakeLists.txt         |  4 ++++
 modules/videoio/cmake/plugin.cmake     |  1 +
 modules/videoio/src/backend_plugin.cpp | 16 ++++++++++++++++
 3 files changed, 21 insertions(+)

diff --git a/modules/videoio/CMakeLists.txt b/modules/videoio/CMakeLists.txt
index 721628325f..bf82bb0eb1 100644
--- a/modules/videoio/CMakeLists.txt
+++ b/modules/videoio/CMakeLists.txt
@@ -31,6 +31,10 @@ file(GLOB videoio_ext_hdrs
   "${CMAKE_CURRENT_LIST_DIR}/include/opencv2/${name}/*.h"
   "${CMAKE_CURRENT_LIST_DIR}/include/opencv2/${name}/legacy/*.h")
 
+if(OPENCV_DEBUG_POSTFIX)
+  ocv_append_source_file_compile_definitions("${CMAKE_CURRENT_LIST_DIR}/src/backend_plugin.cpp" "DEBUG_POSTFIX=${OPENCV_DEBUG_POSTFIX}")
+endif()
+
 # Removing WinRT API headers by default
 list(REMOVE_ITEM videoio_ext_hdrs "${CMAKE_CURRENT_LIST_DIR}/include/opencv2/${name}/cap_winrt.hpp")
 
diff --git a/modules/videoio/cmake/plugin.cmake b/modules/videoio/cmake/plugin.cmake
index 55be1c0ef5..95490f2e34 100644
--- a/modules/videoio/cmake/plugin.cmake
+++ b/modules/videoio/cmake/plugin.cmake
@@ -40,6 +40,7 @@ function(ocv_create_builtin_videoio_plugin name target)
   set_target_properties(${name} PROPERTIES
     CXX_STANDARD 11
     CXX_VISIBILITY_PRESET hidden
+    DEBUG_POSTFIX "${OPENCV_DEBUG_POSTFIX}"
     OUTPUT_NAME "${name}${OPENCV_PLUGIN_VERSION}${OPENCV_PLUGIN_ARCH}"
   )
 
diff --git a/modules/videoio/src/backend_plugin.cpp b/modules/videoio/src/backend_plugin.cpp
index f73a9ad7ac..d8b7c3014e 100644
--- a/modules/videoio/src/backend_plugin.cpp
+++ b/modules/videoio/src/backend_plugin.cpp
@@ -123,6 +123,9 @@ std::string librarySuffix()
         CVAUX_STR(CV_MAJOR_VERSION) CVAUX_STR(CV_MINOR_VERSION) CVAUX_STR(CV_SUBMINOR_VERSION)
     #if (defined _MSC_VER && defined _M_X64) || (defined __GNUC__ && defined __x86_64__)
         "_64"
+    #endif
+    #if defined(_DEBUG) && defined(DEBUG_POSTFIX)
+        CVAUX_STR(DEBUG_POSTFIX)
     #endif
         ".dll";
     return suffix;
@@ -338,6 +341,19 @@ std::vector<FileSystemPath_t> getPluginCandidates(const std::string& baseName)
         results.push_back(path + L"\\" + moduleName);
     }
     results.push_back(moduleName);
+#if defined(_DEBUG) && defined(DEBUG_POSTFIX)
+    if (baseName_u == "FFMPEG")  // backward compatibility
+    {
+        const FileSystemPath_t templ = toFileSystemPath(CVAUX_STR(DEBUG_POSTFIX) ".dll");
+        FileSystemPath_t nonDebugName(moduleName);
+        size_t suf = nonDebugName.rfind(templ);
+        if (suf != FileSystemPath_t::npos)
+        {
+            nonDebugName.replace(suf, suf + templ.size(), L".dll");
+            results.push_back(nonDebugName);
+        }
+    }
+#endif // _DEBUG && DEBUG_POSTFIX
 #else
     CV_LOG_INFO(NULL, "VideoIO pluigin (" << baseName << "): glob is '" << plugin_expr << "', " << paths.size() << " location(s)");
     for (const string & path : paths)