forgecss

forgecss is a C++ CSS parser project that tokenizes CSS input, builds a stylesheet AST, and returns the parsed rules.

Overview

This project demonstrates a CSS parser architecture with separate tokenizer, parser, AST, and logging components.

It supports:

• CSS tokenization into identifiers, selectors, declarations, values, at-rules, functions, dimensions, hashes, and more
• Parsing of style rules, nested rules, and basic at-rules
• Selector parsing for simple selectors, class selectors, attribute selectors, pseudo-classes, and pseudo-elements
• Declaration parsing with values such as keywords, dimensions, colors, and function calls
• Console output of the parsed stylesheet using a simple AST printer

Project structure

• main.cpp - example driver that tokenizes CSS, prints tokens, parses a stylesheet, and dumps the parsed output
• lexer/ - tokenizer implementation
• parser/ - recursive parser for rules, declarations, selectors, and values
• ast/ - AST node definitions for stylesheets, rules, declarations, selectors, and values
• log/ - debug printing helpers for the parsed stylesheet
• TokenType/ - token kind definitions used by the lexer and parser
• forgecss.xcodeproj/ - Xcode project for building the executable on macOS

Usage

1. Open forgecss.xcodeproj in Xcode and build the forgecss target.
2. Run the resulting executable from Xcode or from the terminal.
3. The current main.cpp uses hard-coded CSS examples and prints:
   • the token stream produced by the lexer
   • the parsed stylesheet structure

Example workflow from terminal:

cd forgecss/forgecss
xcodebuild -project ../forgecss.xcodeproj
# or use Xcode directly

Features

• Tokenizes CSS input into a sequence of typed tokens
• Parses selectors and style rules
• Supports nested rules inside style blocks
• Handles @media and other at-rules with nested rule parsing
• Parses declaration values including:
  • numeric dimensions (e.g. 10px)
  • color hashes (e.g. #d9d9d9)
  • functions (e.g. var(--color-outline))
  • identifiers and keywords

Limitations

The current parser is intentionally limited and does not yet support full CSS grammar.

Known gaps include:

• full descendant and combinator selector parsing (e.g. div span, div > span)
• advanced selector groups and complex selector nesting
• full parsing of all CSS at-rule forms and prelude grammar
• complete cascade, specificity, and stylesheet evaluation

Notes

The project is designed as a learning engine for CSS parsing rather than a production CSS processor. It is especially useful for experimenting with lexer/parser architecture and AST modeling in C++.