stet_core/

font_loader.rs

// stet - A PostScript Interpreter
// Copyright (c) 2026 Scott Bowman
// SPDX-License-Identifier: Apache-2.0 OR MIT

//! Font loading pipeline.
//!
//! Loads Type 1 font files from disk, parses them, and creates PostScript
//! font dictionary objects. Includes font name substitution table.

use crate::context::Context;
use crate::dict::DictKey;
use crate::object::{PsObject, PsValue};

// Re-export font substitution data from stet-fonts for backward compatibility.
pub use stet_fonts::{FONT_SUBSTITUTIONS, find_substitution};

/// Try to load a font by name, using the substitution table.
/// Checks embedded files first (for WASM), then falls back to disk.
pub fn load_font_file(
    font_name: &str,
    resource_path: &str,
    files: &crate::file_store::FileStore,
) -> Option<Vec<u8>> {
    // Try embedded files first (for WASM builds)
    let direct_path = format!("{}/{}.t1", resource_path, font_name);
    if let Some(data) = files.get_embedded_file(&direct_path) {
        return Some(data.to_vec());
    }
    if let Some(urw_name) = find_substitution(font_name) {
        let sub_path = format!("{}/{}.t1", resource_path, urw_name);
        if let Some(data) = files.get_embedded_file(&sub_path) {
            return Some(data.to_vec());
        }
    }

    // Fall back to disk I/O
    if let Ok(data) = std::fs::read(&direct_path) {
        return Some(data);
    }
    if let Some(urw_name) = find_substitution(font_name) {
        let sub_path = format!("{}/{}.t1", resource_path, urw_name);
        if let Ok(data) = std::fs::read(&sub_path) {
            return Some(data);
        }
    }

    None
}

/// Load a Type 1 font from data and register it as a PostScript dict in the context.
/// Returns the font dict PsObject.
pub fn load_type1_font(ctx: &mut Context, font_data: &[u8]) -> Result<PsObject, String> {
    let font = crate::type1_parser::parse_type1(font_data)?;

    let save_level = ctx.save_stack.current_level();
    let global = ctx.vm_alloc_mode;
    let created = ctx.save_stack.last_save_id();

    // Create the font dictionary (respects current VM allocation mode)
    let font_dict =
        ctx.dicts
            .allocate_with(30, font.font_name.as_bytes(), save_level, global, created);

    // /FontName → name object
    let name_id = ctx.names.intern(font.font_name.as_bytes());
    ctx.dicts.put(
        font_dict,
        DictKey::Name(ctx.name_cache.n_font_name),
        PsObject::name_lit(name_id),
    );

    // /FontType → Int(1)
    ctx.dicts.put(
        font_dict,
        DictKey::Name(ctx.name_cache.n_font_type),
        PsObject::int(1),
    );

    // /FontMatrix → array of 6 reals
    let fm_items: Vec<PsObject> = font
        .font_matrix
        .iter()
        .map(|&v| PsObject::real(v))
        .collect();
    let fm_entity = ctx
        .arrays
        .allocate_from_with(&fm_items, save_level, global, created);
    ctx.dicts.put(
        font_dict,
        DictKey::Name(ctx.name_cache.n_font_matrix),
        PsObject::array(fm_entity, 6),
    );

    // /FontBBox → array of 4 reals
    let bb_items: Vec<PsObject> = font.font_bbox.iter().map(|&v| PsObject::real(v)).collect();
    let bb_entity = ctx
        .arrays
        .allocate_from_with(&bb_items, save_level, global, created);
    ctx.dicts.put(
        font_dict,
        DictKey::Name(ctx.name_cache.n_font_bbox),
        PsObject::array(bb_entity, 4),
    );

    // /PaintType → Int
    ctx.dicts.put(
        font_dict,
        DictKey::Name(ctx.name_cache.n_paint_type),
        PsObject::int(font.paint_type),
    );

    // /Encoding → array of 256 name objects
    let enc_items: Vec<PsObject> = font
        .encoding
        .iter()
        .map(|name| {
            let id = ctx.names.intern(name.as_bytes());
            PsObject::name_lit(id)
        })
        .collect();
    let enc_entity = ctx
        .arrays
        .allocate_from_with(&enc_items, save_level, global, created);
    ctx.dicts.put(
        font_dict,
        DictKey::Name(ctx.name_cache.n_encoding),
        PsObject::array(enc_entity, 256),
    );

    // /CharStrings → dict mapping glyph names to string objects (encrypted bytes)
    let cs_dict = ctx.dicts.allocate_with(
        font.charstrings.len().max(10),
        b"CharStrings",
        save_level,
        global,
        created,
    );
    for (glyph_name, bytes) in &font.charstrings {
        let glyph_name_id = ctx.names.intern(glyph_name.as_bytes());
        let str_entity = ctx
            .strings
            .allocate_from_with(bytes, save_level, global, created);
        let str_obj = PsObject::string(str_entity, bytes.len() as u32);
        ctx.dicts
            .put(cs_dict, DictKey::Name(glyph_name_id), str_obj);
    }
    ctx.dicts.put(
        font_dict,
        DictKey::Name(ctx.name_cache.n_char_strings),
        PsObject::dict(cs_dict),
    );

    // /Private → dict with lenIV and Subrs (standard Type 1 structure)
    let priv_dict = ctx
        .dicts
        .allocate_with(10, b"Private", save_level, global, created);
    ctx.dicts.put(
        priv_dict,
        DictKey::Name(ctx.name_cache.n_len_iv),
        PsObject::int(font.len_iv as i32),
    );

    // /Subrs → array of string objects (encrypted subroutine bytes) inside Private
    let subr_items: Vec<PsObject> = font
        .subrs
        .iter()
        .map(|bytes| {
            let entity = ctx
                .strings
                .allocate_from_with(bytes, save_level, global, created);
            PsObject::string(entity, bytes.len() as u32)
        })
        .collect();
    let subrs_entity = ctx
        .arrays
        .allocate_from_with(&subr_items, save_level, global, created);
    ctx.dicts.put(
        priv_dict,
        DictKey::Name(ctx.name_cache.n_subrs),
        PsObject::array(subrs_entity, font.subrs.len() as u32),
    );

    ctx.dicts.put(
        font_dict,
        DictKey::Name(ctx.name_cache.n_private),
        PsObject::dict(priv_dict),
    );

    // /FID → unique font ID
    let fid = ctx.next_fid;
    ctx.next_fid += 1;
    ctx.dicts.put(
        font_dict,
        DictKey::Name(ctx.name_cache.n_fid),
        PsObject::int(fid),
    );

    // Register in FontDirectory under the font name
    let font_obj = PsObject::dict(font_dict);
    let font_directory = ctx.font_directory;
    ctx.dict_put_cow(font_directory, DictKey::Name(name_id), font_obj);

    Ok(font_obj)
}

/// Try to find a font by name: check FontDirectory first, then load from disk.
pub fn find_font(ctx: &mut Context, name_bytes: &[u8]) -> Result<PsObject, String> {
    let name_id = ctx.names.intern(name_bytes);
    let key = DictKey::Name(name_id);

    // Check FontDirectory
    if let Some(font_obj) = ctx.dicts.get(ctx.font_directory, &key) {
        return Ok(font_obj);
    }

    // Try to load from disk
    let font_name = String::from_utf8_lossy(name_bytes);
    let resource_path = ctx
        .font_resource_path
        .clone()
        .ok_or_else(|| format!("Font '{}' not found and no resource path set", font_name))?;

    let font_data = load_font_file(&font_name, &resource_path, &ctx.files)
        .ok_or_else(|| format!("Font '{}' not found in {}", font_name, resource_path))?;

    let font_obj = load_type1_font(ctx, &font_data)?;

    // The font may have been registered under a different name (the actual font name
    // from the .t1 file). We need to also register under the requested name.
    let actual_name = get_font_name(ctx, font_obj);
    if actual_name.as_deref() != Some(&*font_name) {
        let font_directory = ctx.font_directory;
        ctx.dict_put_cow(font_directory, key, font_obj);
    }

    Ok(font_obj)
}

/// Extract /FontName from a font dict object.
fn get_font_name(ctx: &Context, font_obj: PsObject) -> Option<String> {
    if let PsValue::Dict(entity) = font_obj.value
        && let Some(name_obj) = ctx
            .dicts
            .get(entity, &DictKey::Name(ctx.name_cache.n_font_name))
        && let PsValue::Name(id) = name_obj.value
    {
        return Some(String::from_utf8_lossy(ctx.names.get_bytes(id)).to_string());
    }
    None
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn test_font_substitution() {
        assert_eq!(find_substitution("Helvetica"), Some("NimbusSans-Regular"));
        assert_eq!(
            find_substitution("Times-Roman"),
            Some("NimbusRoman-Regular")
        );
        assert_eq!(find_substitution("Courier"), Some("NimbusMonoPS-Regular"));
        assert_eq!(find_substitution("Symbol"), Some("StandardSymbolsPS"));
        assert_eq!(find_substitution("NoSuchFont"), None);
    }

    #[test]
    fn test_load_real_font() {
        let font_path = std::path::Path::new(env!("CARGO_MANIFEST_DIR"))
            .join("../../resources/Font/NimbusSans-Regular.t1");
        if !font_path.exists() {
            eprintln!("Skipping test — font file not found");
            return;
        }

        let mut ctx = Context::new();
        let font_data = std::fs::read(&font_path).unwrap();
        let font_obj = load_type1_font(&mut ctx, &font_data).unwrap();

        // Verify it's a dict
        assert!(matches!(font_obj.value, PsValue::Dict(_)));

        // Verify FontName
        if let PsValue::Dict(entity) = font_obj.value {
            let name_obj = ctx
                .dicts
                .get(entity, &DictKey::Name(ctx.name_cache.n_font_name))
                .unwrap();
            if let PsValue::Name(id) = name_obj.value {
                assert_eq!(ctx.names.get_bytes(id), b"NimbusSans-Regular");
            }

            // Verify FontType = 1
            let type_obj = ctx
                .dicts
                .get(entity, &DictKey::Name(ctx.name_cache.n_font_type))
                .unwrap();
            assert_eq!(type_obj.as_i32(), Some(1));

            // Verify CharStrings is a dict with entries
            let cs_obj = ctx
                .dicts
                .get(entity, &DictKey::Name(ctx.name_cache.n_char_strings))
                .unwrap();
            if let PsValue::Dict(cs_entity) = cs_obj.value {
                assert!(ctx.dicts.length(cs_entity) > 100);
            } else {
                panic!("CharStrings should be a dict");
            }
        }

        // Verify it's registered in FontDirectory
        let name_id = ctx.names.intern(b"NimbusSans-Regular");
        assert!(
            ctx.dicts
                .get(ctx.font_directory, &DictKey::Name(name_id))
                .is_some()
        );
    }
}