xo-indentlog: doc: add indentlog docs [WIP]

docs/logging_impl.rst

@@ -0,0 +1,65 @@
+.. _logging_impl:
+
+Logging Components
+==================
+
+Install instructions :doc:`here<install>`
+
+Abstraction tower for *xo-indentlog* logging components:
+
+.. ditaa::
+    :--scale: 0.85
+
+    +------------------------------------------+
+    |               basic_scope                |
+    +------------------------------------------+
+    |                state_impl                |
+    +-----------------------+------------------+
+    |                       |     log_config   |
+    |      log_streambuf    +------------------+
+    |                       |     log_level    |
+    +-----------------------+------------------+
+
+**basic_scope**
+    Primary entry point for scope-indented logging.
+    Lightweight with RAII semantics.
+
+**state_impl**
+    Bookkeeping for internal state, managed by ``basic_scope``.
+
+**log_streambuf**
+    Custom streambuf implementation, buffering in memory.
+
+**log_config**
+    Logging configuration, to control formatting behavior.
+
+**log_level**
+    Categorize log messages by importance for filtering.
+
+.. toctree::
+   :maxdepth: 2
+
+   xo::scope <scope-reference>
+
+
+Log_streambuf
+-------------
+
+Indentlog relies on a custom ``std::streambuf`` implementation, ``xo::log_streambuf``.
+log_streambuf captures content in an internal vector, expanding it on demand.
+To support pretty-printing, log_streambuf tracks current position relative to left margin
+
+.. uml::
+    :caption: log_streambuf
+    :scale: 99%
+    :align: center
+
+    class streambuf {
+    }
+
+    class log_streambuf {
+    - solpos_: size_t
+    - buf_v_: vector
+    }
+
+    streambuf <|-- log_streambuf