Merge pull request #20370 from ddacw:stub-gen-next

Python typing stub generation #20370

Add stub generation to `gen2.py`, addressing #14590.

### 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 other license that is incompatible with OpenCV
- [x] The PR is proposed to proper branch
- [x] There is reference to 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.
- [ ] The feature is well documented and sample code can be built with the project CMake

modules/python/bindings/CMakeLists.txt

@@ -76,11 +76,14 @@ set(cv2_generated_files
 
 string(REPLACE ";" "\n" opencv_hdrs_ "${opencv_hdrs}")
 file(WRITE "${CMAKE_CURRENT_BINARY_DIR}/headers.txt" "${opencv_hdrs_}")
+file(GLOB_RECURSE typing_stubs_generation_files "${PYTHON_SOURCE_DIR}/src2/typing_stubs_generation/*.py")
 add_custom_command(
     OUTPUT ${cv2_generated_files}
     COMMAND "${PYTHON_DEFAULT_EXECUTABLE}" "${PYTHON_SOURCE_DIR}/src2/gen2.py" "${CMAKE_CURRENT_BINARY_DIR}" "${CMAKE_CURRENT_BINARY_DIR}/headers.txt"
     DEPENDS "${PYTHON_SOURCE_DIR}/src2/gen2.py"
             "${PYTHON_SOURCE_DIR}/src2/hdr_parser.py"
+            "${typing_stubs_generation_files}"
+            "${PYTHON_SOURCE_DIR}/src2/typing_stubs_generator.py"
             # not a real build dependency (file(WRITE) result): ${CMAKE_CURRENT_BINARY_DIR}/headers.txt
             ${opencv_hdrs}
     COMMENT "Generate files for Python bindings and documentation"
@@ -88,6 +91,10 @@ add_custom_command(
 
 add_custom_target(gen_opencv_python_source DEPENDS ${cv2_generated_files})
 
+if(TARGET copy_opencv_typing_stubs)
+  add_dependencies(copy_opencv_typing_stubs gen_opencv_python_source)
+endif()
+
 set(cv2_custom_hdr "${CMAKE_CURRENT_BINARY_DIR}/pyopencv_custom_headers.h")
 set(cv2_custom_hdr_str "//user-defined headers\n")
 foreach(uh ${opencv_userdef_hdrs})