feat: enable MODMESH_USE_PYSIDE to on, by default

refactor: remove the switch

refactor: comments

Author: Telomelonia

CMakeLists.txt

@@ -16,6 +16,9 @@ endif()
 option(BUILD_QT "build with QT" ON)
 message(STATUS "BUILD_QT: ${BUILD_QT}")
 
+# PySide6 is required since 2023 (see issue https://github.com/solvcon/modmesh/issues/220)
+message(STATUS "PySide6 support: REQUIRED")
+
 option(BUILD_METAL "build with Metal" OFF)
 message(STATUS "BUILD_METAL: ${BUILD_METAL}")
 if(BUILD_METAL)
@@ -138,6 +141,7 @@ set(MODMESH_INCLUDE_DIR "${CMAKE_CURRENT_LIST_DIR}/cpp" CACHE INTERNAL "")
 
 include_directories(${MODMESH_INCLUDE_DIR})
 
+add_compile_definitions(MODMESH_USE_PYSIDE)
 execute_process(
     COMMAND python3 -c "import sys, os, PySide6; sys.stdout.write(os.path.dirname(PySide6.__file__))"
     OUTPUT_VARIABLE PYSIDE6_PYTHON_PACKAGE_PATH