Add target_top_level_statement command

scripts/cmake/xtd_commands.cmake

@@ -325,6 +325,57 @@ macro(target_startup ...)
   set(PROJECT_SOURCES "${PROJECT_SOURCES};${STARTUP_FILE}")
 endmacro()
 
+## @brief Generates top-level statements with specified source file.
+## @param TOP_LEVEL_FILE the file that contains the content of the main entry point.
+## @remarks Do not use this method of startup_(...) is present in your files or if you use standard c++ main() method.
+## @remarks Call only once by project.
+## @remarks This method must be call before target_type().
+## @remarks This method is optional. 
+## @par Examples
+## ```cpp
+##  cmake_minimum_required(VERSION 3.20)
+##
+##  project(my_project)
+##  find_package(xtd REQUIRED)
+##  add_sources(my_project.cpp)
+##
+##  target_top_level_statement(my_project.cpp)
+##  target_type(GUI_APPLICATION)
+## ```
+macro(target_top_level_statement TOP_LEVEL_FILE)
+  message(VERBOSE "Add top level statement [\"${TOP_LEVEL_FILE}\"]...")
+  set(STARTUP_FILE properties/startup.cpp)
+  string(REPLACE "${CMAKE_CURRENT_SOURCE_DIR}/" "" TOP_LEVEL_FILE ${TOP_LEVEL_FILE})
+  file(RELATIVE_PATH STARTUP_OBJECT_RELATIVE_PATH ${CMAKE_CURRENT_SOURCE_DIR}/Properties ${CMAKE_CURRENT_SOURCE_DIR}/${TOP_LEVEL_FILE})
+  set(INCLUDE_FILE "#include \"${STARTUP_OBJECT_RELATIVE_PATH}\"\n")
+  file(WRITE ${STARTUP_FILE}
+    "#pragma region xtd generated code\n"
+    "// This code was generated by CMake script.\n"
+    "//\n"
+    "// Changes to this file may cause incorrect behavior and will be lost if the code is regenerated.\n"
+    "\n"
+    "#include <xtd/xtd>\n"
+    "\n"
+    "auto main() -> int {\n"
+    "  xtd::startup::safe_run([] {\n"
+    "    using namespace xtd;\n"
+    "    using namespace xtd::collections::generic;\n"
+    "    using namespace xtd::io;\n"
+    "    //using namespace xtd::linq;\n"
+    "    //using namespace xtd::net::http;\n"
+    "    using namespace xtd::threading;\n"
+    "    using namespace xtd::threading::tasks;\n"
+    "    \n"
+    "    ${INCLUDE_FILE}"
+    "  });\n"
+    "}\n"
+    "#pragma endregion\n"
+  )
+  #source_group(src\\properties FILES ${STARTUP_FILE})
+  auto_source_group(${STARTUP_FILE}) 
+  set(PROJECT_SOURCES "${PROJECT_SOURCES};${STARTUP_FILE}")
+endmacro()
+
 ## @brief Specifies the type of application to build.
 ## @param TYPE Type of application.
 ## Possible values :