a day ago
- CSS lacks variables, leading to hard-coded constants like theme colors that are difficult to maintain.
- m4 is a macro processor that can substitute strings, enabling easy updates to CSS values.
- Basic usage: define a macro with `define(`NAME', `value')` and use it in CSS; run `m4 file.css.m4 > file.css`.
- Quoting in m4 uses backtick (`) as open and apostrophe (') as close to prevent macro expansion.
- The `dnl` directive deletes the newline after a define line to avoid extra blank lines in output.
- Parentheses after macro names (e.g., `THEMECOLOR()`) allow macros to be placed adjacent to other text.
- External files can be included via `include()` or `sinclude()` for modular CSS.
- Integer math is possible with `eval()`, e.g., `eval(XPOS + 40)` for computed positions.
- m4 can also be used for HTML, but caution is needed due to lack of multibyte support and potential complexity.
- Other CSS-specific tools like Less and Sass exist, but m4 is lightweight, POSIX-compliant, and widely available.