update styleguide

.clang-format

@@ -31,4 +31,21 @@ PointerAlignment: Left
 SpaceAfterCStyleCast: false # want true, but has issues with clang-format-12
 SpaceAfterTemplateKeyword: false
 Standard: c++17
+# TODO Does not work reliable, yet. Do not use in automatic CI pipeline!
+# Relies on having <> vs. "" correctly set, is missing POSIX/Win32 headers and other edge cases.
+# Uncomment to use locally for at least semi automated fixup.
+#IncludeBlocks: Regroup
+#IncludeCategories:
+#  # C headers (https://en.cppreference.com/w/cpp/header)
+#  - Regex:    '<(assert|complex|ctype|errno|fenv|float|inttypes|iso646|limits|locale|math|setjmp|signal|stdalign|stdarg|stdatomic|stdbool|stddef|stdint|stdio|stdlib|string|tgmath|time|uchar|wchar|wctype)\.h>'
+#    Priority: 1
+#  # C++ headers: assume <>, no slash, no extension
+#  - Regex:    '<([A-Za-z0-9_])+>'
+#    Priority: 2
+#  # Library headers: all other assume <>
+#  - Regex:    '<([A-Za-z0-9./_-])+>'
+#    Priority: 3
+#  # Local headers: assume ""
+#  - Regex:    '"([A-Za-z0-9./_-])+"'
+#    Priority: 4
 ...

docs/styleguide.md

@@ -43,11 +43,13 @@ There, the original formatting should be kept.
 ## File Organization
 
 - Use `#pragma once` and do not use include guards. 
-- Split includes into 4 groups, each group is ordered alphabetically, empty line between groups:
-  1. Corresponding Header to the current .cpp file (with `""`).
-  2. System Includes (with `<>`)
-  3. External Library Includes (with `<>`[^6])
-  4. MegaMol internal includes (with `""`)
+- Split includes into groups, each group is ordered alphabetically, empty line between groups:
+  1. Corresponding header to the current .cpp file (with `""`).
+  2. C system headers (with `<>`[^6])
+  3. C++ STL headers (with `<>`[^6])
+  4. External library headers (with `<>`[^6])
+  5. MegaMol internal headers (headers in this repository) (with `""`)
+  6. Conditional includes requiring `#ifdef` after all others
 - Header files use the extension `.h`, source files `.cpp`
 - Files names must match the corresponding class name (also in `UpperCamelCase`).
 - Directory names must match the corresponding namespace (at least for top level categorisation, additional subdirectories may or may not introduce an additional namespace level).