hunter: add Qt5 backend with static link support

When static linking, Qt5 resources must the initialized manually

The file static_opencv_qt_resources.cpp initializes the resources
for the highgui icons. This patch uses the QtCMakeExtra Hunter
project to add it as an interface source file.

Add target Qt5::Widgets to opencv_highgui target

Author: pretyman

cmake/OpenCVFindLibsGUI.cmake

@@ -31,6 +31,13 @@ if(WITH_QT)
     # BUG: Qt5Config.cmake script can't handle components properly: find_package(QT NAMES Qt6 Qt5 REQUIRED NO_MODULE COMPONENTS Core Gui Widgets Test Concurrent)
     ocv_find_package_Qt(6 QUIET)
     if(NOT QT_FOUND)
+      hunter_add_package(Qt)
+      find_package(Qt5Core)
+      find_package(Qt5Gui)
+      find_package(Qt5Widgets)
+      find_package(Qt5Test)
+      find_package(Qt5Concurrent)
+
       ocv_find_package_Qt(5 QUIET)
     endif()
     if(NOT QT_FOUND)

cmake/templates/OpenCVConfig.cmake.in

@@ -387,3 +387,37 @@ endif()
 if("@OPENEXR_FOUND@")
   find_dependency(OpenEXR CONFIG)
 endif()
+
+# AWP: Qt5 dependencies -- start
+if("@Qt5Core_FOUND@")
+  find_dependency(Qt5Core)
+endif()
+
+if("@Qt5Gui_FOUND@")
+  find_dependency(Qt5Gui)
+endif()
+
+if("@Qt5Widgets_FOUND@")
+  find_dependency(Qt5Widgets)
+  _qt_cmake_extra_helpers_add_interface(opencv_highgui Qt5::Widgets)
+  if(NOT "@BUILD_SHARED_LIBS@")
+    # function from Hunter's QtCMakeExtra project
+    _qt_cmake_extra_helpers_add_source(
+        opencv_highgui "static_opencv_qt_resources.cpp"
+    )
+  endif()
+endif()
+
+if("@Qt5Test_FOUND@")
+  find_dependency(Qt5Test)
+endif()
+
+if("@Qt5Concurrent_FOUND@")
+  find_dependency(Qt5Concurrent)
+endif()
+
+if("@Qt5OpenGL_FOUND@")
+  find_dependency(Qt5OpenGL)
+endif()
+# AWP: Qt5 dependencies -- end
+

modules/highgui/CMakeLists.txt

@@ -88,6 +88,17 @@ elseif(HAVE_QT)
       QT6_ADD_RESOURCES(_RCC_OUTFILES ${CMAKE_CURRENT_LIST_DIR}/src/window_QT.qrc)
       QT6_WRAP_CPP(_MOC_OUTFILES ${CMAKE_CURRENT_LIST_DIR}/src/window_QT.h)
     elseif(QT_VERSION_MAJOR EQUAL 5)
+      # Hunter patch to load qt resources when static linking
+      # Hunter has only Qt5, so its guarded by if(HAVE_QT5)
+      if(NOT BUILD_SHARED_LIBS)
+        install(
+          FILES
+            ${CMAKE_CURRENT_LIST_DIR}/static_opencv_qt_resources.cpp
+          DESTINATION
+            "src/qt/plugins"
+        )
+      endif()
+
       QT5_ADD_RESOURCES(_RCC_OUTFILES ${CMAKE_CURRENT_LIST_DIR}/src/window_QT.qrc)
       QT5_WRAP_CPP(_MOC_OUTFILES ${CMAKE_CURRENT_LIST_DIR}/src/window_QT.h)
     else()

modules/highgui/static_opencv_qt_resources.cpp

@@ -0,0 +1,22 @@
+/**
+ * Part of the Hunter patch for static linking OpenCV with Qt
+ * Initializes the resources for the highgui window icons
+ */
+
+#include <QtCore>
+
+inline void static_opencv_qt_resources() {
+	Q_INIT_RESOURCE(window_QT);
+}
+
+namespace {
+
+    struct static_opencv_qt_resources_initializer{
+        static_opencv_qt_resources_initializer() {
+            static_opencv_qt_resources();
+        }
+    };
+    
+    static_opencv_qt_resources_initializer global_instance;
+}
+