Updated documentation

Signed-off-by: Gonzalo de Pedro <[email protected]>

source/Concepts/Advanced/About-Internal-Interfaces.rst

@@ -201,16 +201,20 @@ of CMake and Ament. To simplify the explanation of this mechanism let's separate
 -  ``Generator`` projects, which are the ones that have the templates and logic to generate code.
 -  ``Interface`` projects, which are the ones that need code to be generated, they have the parameters to generate code.
 
-For instance, typesupport packages that generate code for a particular dds implementation are *Generator* packages, same case that rosidl which
+For instance, typesupport packages that generate code for a particular dds implementation are ``Generator`` packages, same case that rosidl which
 generates code from ros idl (.msg, .action, etc) files.
 
-*Interface* projects are typically projects that define messages, actions and services. Which have .msg files with rosidl defined on them which are
-used by *Generator* projects to create code. A package that calls rosidl_generate_interfaces CMake macro is a *Interface* project.
+``Interface`` projects are typically projects that define messages, actions and services. Which have .msg files with rosidl defined on them which are
+used by ``Interface`` projects to crete code. A package that calls rosidl_generate_interfaces CMake macro is a ``Interface`` project.
 
 Code generation workflow
-------------------------
+-------------------------
+
+On workspace build, the ``generator`` packages, registers portions of CMake code as an ament_extension under different keys:
 
-On workspace build, the *generator* packages, registers a portion of CMake code as an ament_extension under 'rosidl_generate_idl_interfaces' key.
+-  ``rosidl_create_type_descriptions_extensions`` : Calls type support description extensions(generate hashes for typessupports)
+-  ``rosidl_write_generator_arguments_extensions``: Generate the arguments files.
+-  ``rosidl_generate_idl_interfaces``: After files are generated, create artifacts, export dependencies.
 
 Hook registration on CodeGenerator project build
 
@@ -221,28 +225,40 @@ Hook registration on CodeGenerator project build
     participant ament_package
     participant ament_register_extension
     CodeGenerator_cmake->>ament_package: CONFIG_EXTRAS
+    ament_package->>ament_register_extension: rosidl_create_type_descriptions_extensions, cmake_code_hook
+    ament_package->>ament_register_extension: rosidl_write_generator_arguments_extensions, cmake_code_hook
     ament_package->>ament_register_extension: rosidl_generate_idl_interfaces, cmake_code_hook
     Note right of ament_package: Execute a cmake.in template with variables and a cmake code hook.
 
 
-When the *interface* package, during its build process, calls the 'rosidl_generate_interfaces' macro, the extensions that were registered for each of the
-*generator* packages, get called. Said extensions have the code to generate sources for each of the IDL interfaces. Then, code is added to an artifact
-(a library) and dependiences are exported for code to be build and installed.
+When the ``interface`` package, during its build process, calls the 'rosidl_generate_interfaces' macro, the extensions that were registered for each of the
+``generator`` packages, get called. On 'rosidl_write_generator_arguments_extensions' arguments files are generated with all parameters required to call the templates engine.
+After collecting all the arguments files, the extension calls the template engine for all the arguments files at once. Once code is generated,
+the 'rosidl_generate_idl_interfaces' extensiones are called to get code added to an artifact (a library) and export dependiences.
 
 .. mermaid::
 
     sequenceDiagram
     participant project_with_rosidl_files
     participant rosidl_generate_interfaces
+    participant rosidl_create_type_descriptions_extensions_HOOK
     participant rosidl_generate_idl_interfaces_HOOK
+    participant rosidl_write_generator_arguments_extensions_HOOK
     participant generate_arguments_file
     participant rosidl_generator
     project_with_rosidl_files->>rosidl_generate_interfaces: path_to_idl_files
-    loop ForEach Hook
-        rosidl_generate_interfaces->>rosidl_generate_idl_interfaces_HOOK: path_to_idl_files, parameters
-        rosidl_generate_idl_interfaces_HOOK->>generate_arguments_file: template_parameters
+    loop ForEach rosidl_create_type_descriptions_extensions Hook
+        rosidl_generate_interfaces->>rosidl_create_type_descriptions_extensions_HOOK: path_to_idl_files, parameters
+    end
+    loop ForEach rosidl_write_generator_arguments_extensions Hook
+        rosidl_generate_interfaces->>rosidl_write_generator_arguments_extensions_HOOK: path_to_idl_files, parameters
         activate generate_arguments_file
-        generate_arguments_file->>rosidl_generate_idl_interfaces_HOOK: arguments_file
+        rosidl_write_generator_arguments_extensions_HOOK->>generate_arguments_file: path_to_idl_files, parameters
+        generate_arguments_file->>rosidl_write_generator_arguments_extensions_HOOK: arguments_file
         deactivate generate_arguments_file
-        rosidl_generate_idl_interfaces_HOOK->>rosidl_generator: arguments_file
+        rosidl_write_generator_arguments_extensions_HOOK->>rosidl_generate_interfaces: arguments_file
+    end
+    rosidl_generate_interfaces->>rosidl_generator: [arguments_files]
+    loop ForEach rosidl_generate_idl_interfaces Hook
+        rosidl_generate_interfaces->>rosidl_generate_idl_interfaces_HOOK: generated_files
     end