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build_font_css.php

Path: build/build_font_css.php | Language: PHP | Lines: ~225

Generates CSS @font-face declarations from a structured font specification file.

Overview​

This script is the primary font CSS generator for gwern.net. It reads a declarative font specification from font_spec.php and outputs two CSS files: a complete font stylesheet (fonts-GENERATED.css) and a subset containing only critical fonts for initial page load (initial-fonts-GENERATED.css).

The specification file uses a custom tab-delimited format that describes fonts with their weights, filenames, italic variants, and CSS properties like font-display and unicode-range. The script supports special !inline command blocks that mark certain font entries as critical for inlining into the initial CSS.

This is a foundational build step that runs early in the build process, as the generated CSS files are dependencies for versioning and inlining steps downstream.

Key Functions/Variables​

generate_entries($spec_block) Parses a multi-line font specification block into an array of font entry objects. Each entry inherits base properties (name, base_path, format) and adds specific properties (weight, filename, italic variants).

construct_rule($entry, $italic = false) Constructs a complete CSS @font-face rule from a font entry object. Handles italic path transformation via regex patterns specified in the spec file.

should_inline($candidate_entry, $italic = false) Determines whether a font entry should be included in the initial CSS file by matching it against the global $entries_to_inline list populated by !inline command blocks.

process_command_block($command_block) Processes special command blocks in the spec file (currently only !inline), which mark font entries that should be included in the critical initial CSS.

kv_tokenize($line) Parses tab-delimited key-value pairs from spec file lines. Handles special cases like backtick-prefixed values and multi-part italic specifications.

Global variables:

  • $entries_to_inline: Array of font entries marked for inclusion in initial CSS
  • $bare_fields: Field names that can be inferred from position (name, base_path, format)
  • $formats: Maps file extensions (ttf, otf) to CSS format strings (truetype, opentype)

Input/Output​

Inputs:

  • /static/font/font_spec.php - Tab-delimited font specification file with metadata about each font family, weight, and variant

Outputs:

  • /css/fonts-GENERATED.css - Complete CSS file with all font-face declarations
  • /css/initial-fonts-GENERATED.css - Subset containing only fonts marked for initial page load

Usage​

Invoked directly by sync.sh during the CSS build phase:

php build/build_font_css.php

The script outputs progress to stdout and populates the $updated_files array for tracking by the build system.

See Also​