Implement subsetting engine 🚀

Cargo.toml

@@ -9,3 +9,4 @@ pdf = { path = "../pdf" }
 opentype = { path = "../opentype" }
 unicode-segmentation = "1.2"
 unicode-xid = "0.1.0"
+byteorder = "1"

src/font.rs

@@ -0,0 +1,411 @@
+//! Font utility and subsetting.
+
+use std::fmt;
+use std::io::{self, Cursor};
+use std::collections::HashMap;
+use byteorder::{BE, ReadBytesExt, WriteBytesExt};
+use opentype::{OpenTypeReader, Outlines, TableRecord, Tag};
+use opentype::tables::{Header, CharMap, MaximumProfile, HorizontalMetrics};
+
+/// An font wrapper which allows to subset a font.
+pub struct Font {
+    program: Vec<u8>,
+}
+
+impl Font {
+    /// Create a new font from a font program.
+    pub fn new(program: Vec<u8>) -> Font {
+        Font { program }
+    }
+
+    /// Generate a subsetted version of this font including only the chars listed in
+    /// `chars`.
+    ///
+    /// The resulting pair contains the new font data and the new glyph mapping.
+    ///
+    /// All needed tables will be included (returning an error if a table was not present
+    /// in the  source font) and optional tables will be included if there were present
+    /// in the source font.
+    pub fn subsetted<C, I1, S1, I2, S2>(
+        &self,
+        chars: C,
+        needed_tables: I1,
+        optional_tables: I2
+    ) -> Result<(Vec<u8>, HashMap<char, u16>), SubsettingError>
+    where
+        C: IntoIterator<Item=char>,
+        I1: IntoIterator<Item=S1>, S1: AsRef<str>,
+        I2: IntoIterator<Item=S2>, S2: AsRef<str>
+    {
+        let mut chars: Vec<char> = chars.into_iter().collect();
+        chars.sort();
+
+        let mut cursor = Cursor::new(&self.program);
+        let mut reader = OpenTypeReader::new(&mut cursor);
+        let outlines = reader.outlines()?;
+        let mut tables = reader.tables()?.to_vec();
+        tables.sort_by_key(|r| r.tag);
+
+        Subsetter {
+            program: &self.program,
+            reader,
+            outlines,
+            tables,
+            cmap: None,
+            hmtx: None,
+            loca: None,
+            chars,
+            records: Vec::new(),
+            body: Vec::new(),
+        }.subset(needed_tables, optional_tables)
+    }
+}
+
+struct Subsetter<'p> {
+    // Original font
+    program: &'p [u8],
+    reader: OpenTypeReader<'p, Cursor<&'p Vec<u8>>>,
+    outlines: Outlines,
+    tables: Vec<TableRecord>,
+    cmap: Option<CharMap>,
+    hmtx: Option<HorizontalMetrics>,
+    loca: Option<Vec<u32>>,
+
+    // Subsetted font
+    chars: Vec<char>,
+    records: Vec<TableRecord>,
+    body: Vec<u8>,
+}
+
+impl<'p> Subsetter<'p> {
+    fn subset<I1, S1, I2, S2>(mut self, needed_tables: I1, optional_tables: I2)
+    -> SubsetResult<(Vec<u8>, HashMap<char, u16>)>
+    where
+        I1: IntoIterator<Item=S1>, S1: AsRef<str>,
+        I2: IntoIterator<Item=S2>, S2: AsRef<str>
+    {
+        // Iterate through the needed tables first
+        for table in needed_tables.into_iter() {
+            let table = table.as_ref();
+            let tag: Tag = table.parse()
+                .map_err(|_| SubsettingError::UnsupportedTable(table.to_string()))?;
+
+            if self.contains(tag) {
+                self.write_table(tag)?;
+            } else {
+                return Err(SubsettingError::MissingTable(tag.to_string()));
+            }
+        }
+
+        // Now iterate through the optional tables
+        for table in optional_tables.into_iter() {
+            let table = table.as_ref();
+            let tag: Tag = table.parse()
+                .map_err(|_| SubsettingError::UnsupportedTable(table.to_string()))?;
+
+            if self.contains(tag) {
+                self.write_table(tag)?;
+            }
+        }
+
+        self.write_header()?;
+
+        let mapping = self.chars.into_iter().enumerate().map(|(i, c)| (c, i as u16))
+            .collect::<HashMap<char, u16>>();
+
+        Ok((self.body, mapping))
+    }
+
+    fn write_header(&mut self) -> SubsetResult<()> {
+        // Create an output buffer
+        let header_len = 12 + self.records.len() * 16;
+        let mut header = Vec::with_capacity(header_len);
+
+        let num_tables = self.records.len() as u16;
+
+        // The highester power lower than the table count.
+        let mut max_power = 1u16;
+        while max_power * 2 <= num_tables {
+            max_power *= 2;
+        }
+        max_power = std::cmp::min(max_power, num_tables);
+
+        let search_range = max_power * 16;
+        let entry_selector = (max_power as f32).log2() as u16;
+        let range_shift = num_tables * 16 - search_range;
+
+        // Write the base header
+        header.write_u32::<BE>(match self.outlines {
+            Outlines::TrueType => 0x00010000,
+            Outlines::CFF => 0x4f54544f,
+        })?;
+        header.write_u16::<BE>(num_tables)?;
+        header.write_u16::<BE>(search_range)?;
+        header.write_u16::<BE>(entry_selector)?;
+        header.write_u16::<BE>(range_shift)?;
+
+        // Write the table records
+        for record in &self.records {
+            header.extend(record.tag.value());
+            header.write_u32::<BE>(record.check_sum)?;
+            header.write_u32::<BE>(header_len as u32 + record.offset)?;
+            header.write_u32::<BE>(record.length)?;
+        }
+
+        header.append(&mut self.body);
+        self.body = header;
+
+        Ok(())
+    }
+
+    fn write_table(&mut self, tag: Tag) -> SubsetResult<()> {
+        match tag.value() {
+            b"head" | b"cvt " | b"prep" | b"fpgm" | b"name" | b"post" | b"OS/2" => {
+                self.copy_table(tag)
+            },
+            b"hhea" => {
+                let table = self.get_table_data(tag)?;
+                let glyph_count = self.chars.len() as u16;
+                self.write_table_body(tag, |this| {
+                    this.body.extend(&table[..table.len() - 2]);
+                    Ok(this.body.write_u16::<BE>(glyph_count)?)
+                })
+            },
+            b"maxp" => {
+                let table = self.get_table_data(tag)?;
+                let glyph_count = self.chars.len() as u16;
+                self.write_table_body(tag, |this| {
+                    this.body.extend(&table[..4]);
+                    this.body.write_u16::<BE>(glyph_count)?;
+                    Ok(this.body.extend(&table[6..]))
+                })
+            },
+            b"hmtx" => {
+                self.write_table_body(tag, |this| {
+                    this.read_cmap()?;
+                    this.read_hmtx()?;
+                    let cmap = this.cmap.as_ref().unwrap();
+                    let metrics = this.hmtx.as_ref().unwrap();
+
+                    for &c in &this.chars {
+                        let glyph_id = take(cmap.get(c), c)?;
+                        let metrics = take(metrics.get(glyph_id), c)?;
+
+                        this.body.write_i16::<BE>(metrics.advance_width)?;
+                        this.body.write_i16::<BE>(metrics.left_side_bearing)?;
+                    }
+                    Ok(())
+                })
+            },
+            b"loca" => {
+                self.write_table_body(tag, |this| {
+                    this.read_cmap()?;
+                    this.read_loca()?;
+                    let cmap = this.cmap.as_ref().unwrap();
+                    let loca = this.loca.as_ref().unwrap();
+
+                    let mut offset = 0;
+                    for &c in &this.chars {
+                        this.body.write_u32::<BE>(offset)?;
+                        let glyph = take(cmap.get(c), c)? as usize;
+                        let len = take(loca.get(glyph + 1), c)? - take(loca.get(glyph), c)?;
+                        offset += len;
+                    }
+                    this.body.write_u32::<BE>(offset)?;
+                    Ok(())
+                })
+            },
+            b"glyf" => {
+                self.write_table_body(tag, |this| {
+                    let table = this.get_table_data(tag)?;
+                    this.read_cmap()?;
+                    this.read_loca()?;
+                    let cmap = this.cmap.as_ref().unwrap();
+                    let loca = this.loca.as_ref().unwrap();
+
+                    for &c in &this.chars {
+                        let glyph = take(cmap.get(c), c)? as usize;
+                        let start = *take(loca.get(glyph), c)? as usize;
+                        let end = *take(loca.get(glyph + 1), c)? as usize;
+                        let shapes = table.get(start..end).ok_or(SubsettingError::InvalidFont)?;
+                        this.body.extend(shapes);
+                    }
+                    Ok(())
+                })
+            },
+            b"cmap" => {
+                // Always uses format 12 for simplicity
+                self.write_table_body(tag, |this| {
+                    // Find out which chars are in consecutive groups
+                    let mut groups = Vec::new();
+                    let len = this.chars.len();
+                    let mut i = 0;
+                    while i < len {
+                        let start = i;
+                        while i + 1 < len && this.chars[i+1] as u32 == this.chars[i] as u32 + 1 {
+                            i += 1;
+                        }
+                        groups.push((this.chars[start], this.chars[i], start));
+                        i += 1;
+                    }
+
+                    // Table header
+                    this.body.write_u16::<BE>(0)?;
+                    this.body.write_u16::<BE>(1)?;
+                    this.body.write_u16::<BE>(3)?;
+                    this.body.write_u16::<BE>(1)?;
+                    this.body.write_u32::<BE>(12)?;
+
+                    // Subtable header
+                    this.body.write_u16::<BE>(12)?;
+                    this.body.write_u16::<BE>(0)?;
+                    this.body.write_u32::<BE>((16 + 12 * groups.len()) as u32)?;
+                    this.body.write_u32::<BE>(0)?;
+                    this.body.write_u32::<BE>(groups.len() as u32)?;
+
+                    // Subtable body
+                    for group in &groups {
+                        this.body.write_u32::<BE>(group.0 as u32)?;
+                        this.body.write_u32::<BE>(group.1 as u32)?;
+                        this.body.write_u32::<BE>(group.2 as u32)?;
+                    }
+
+                    Ok(())
+                })
+            },
+
+            _ => Err(SubsettingError::UnsupportedTable(tag.to_string())),
+        }
+    }
+
+    fn copy_table(&mut self, tag: Tag) -> SubsetResult<()> {
+        self.write_table_body(tag, |this| {
+            let table = this.get_table_data(tag)?;
+            Ok(this.body.extend(table))
+        })
+    }
+
+    fn write_table_body<F>(&mut self, tag: Tag, writer: F) -> SubsetResult<()>
+    where F: FnOnce(&mut Self) -> SubsetResult<()> {
+        let start = self.body.len();
+        writer(self)?;
+        let end = self.body.len();
+        while (self.body.len() - start) % 4 != 0 {
+            self.body.push(0);
+        }
+
+        Ok(self.records.push(TableRecord {
+            tag,
+            check_sum: calculate_check_sum(&self.body[start..]),
+            offset: start as u32,
+            length: (end - start) as u32,
+        }))
+    }
+
+    fn get_table_data(&self, tag: Tag) -> SubsetResult<&'p [u8]> {
+        let record = match self.tables.binary_search_by_key(&tag, |r| r.tag) {
+            Ok(index) => &self.tables[index],
+            Err(_) => return Err(SubsettingError::MissingTable(tag.to_string())),
+        };
+
+        self.program.get(record.offset as usize .. (record.offset + record.length) as usize)
+            .ok_or(SubsettingError::InvalidFont)
+    }
+
+    fn contains(&self, tag: Tag) -> bool {
+        self.tables.binary_search_by_key(&tag, |r| r.tag).is_ok()
+    }
+
+    fn read_cmap(&mut self) -> SubsetResult<()> {
+        Ok(if self.cmap.is_none() {
+            self.cmap = Some(self.reader.read_table::<CharMap>()?);
+        })
+    }
+
+    fn read_hmtx(&mut self) -> SubsetResult<()> {
+        Ok(if self.hmtx.is_none() {
+            self.hmtx = Some(self.reader.read_table::<HorizontalMetrics>()?);
+        })
+    }
+
+    fn read_loca(&mut self) -> SubsetResult<()> {
+        Ok(if self.loca.is_none() {
+            let mut table = self.get_table_data("loca".parse().unwrap())?;
+            let format = self.reader.read_table::<Header>()?.index_to_loc_format;
+            let count = self.reader.read_table::<MaximumProfile>()?.num_glyphs + 1;
+
+            let loca = if format == 0 {
+                (0..count).map(|_| table.read_u16::<BE>()
+                    .map(|x| (x as u32) * 2))
+                    .collect::<io::Result<Vec<u32>>>()
+            } else {
+                (0..count).map(|_| table.read_u32::<BE>())
+                    .collect::<io::Result<Vec<u32>>>()
+            }?;
+
+            self.loca = Some(loca);
+        })
+    }
+}
+
+
+/// Calculate a checksum over the sliced data as sum of u32's.
+/// The data length has to be a multiple of four.
+fn calculate_check_sum(data: &[u8]) -> u32 {
+    let mut sum = 0u32;
+    data.chunks_exact(4).for_each(|c| {
+        sum = sum.wrapping_add(
+            ((c[0] as u32) << 24)
+          + ((c[1] as u32) << 16)
+          + ((c[2] as u32) << 8)
+          + (c[3] as u32)
+        );
+    });
+    sum
+}
+
+/// Returns an error about a missing character or the wrapped data.
+fn take<T>(opt: Option<T>, c: char) -> SubsetResult<T> {
+    opt.ok_or(SubsettingError::MissingCharacter(c))
+}
+
+
+type SubsetResult<T> = Result<T, SubsettingError>;
+
+/// A failure when subsetting a font.
+#[derive(Debug)]
+pub enum SubsettingError {
+    MissingTable(String),
+    UnsupportedTable(String),
+    MissingCharacter(char),
+    InvalidFont,
+    FontError(opentype::Error),
+    IoError(io::Error),
+}
+
+impl From<io::Error> for SubsettingError {
+    fn from(err: io::Error) -> SubsettingError {
+        SubsettingError::IoError(err)
+    }
+}
+
+impl From<opentype::Error> for SubsettingError {
+    fn from(err: opentype::Error) -> SubsettingError {
+        SubsettingError::FontError(err)
+    }
+}
+
+impl fmt::Display for SubsettingError {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        use SubsettingError::*;
+        write!(f, "subsetting error: ")?;
+        match self {
+            MissingTable(table) => write!(f, "missing table: {}", table),
+            UnsupportedTable(table) => write!(f, "unsupported table: {}", table),
+            MissingCharacter(c) => write!(f, "missing character: {}", c),
+            InvalidFont => write!(f, "invalid font"),
+            FontError(err) => write!(f, "font error: {}", err),
+            IoError(err) => write!(f, "io error: {}", err),
+        }
+    }
+}

src/lib.rs

@@ -23,6 +23,7 @@
 
 mod pdf;
 mod utility;
+pub mod font;
 pub mod parsing;
 pub mod doc;
 

src/pdf.rs

@@ -2,7 +2,7 @@
 
 use std::fmt;
 use std::io::{self, Write, Cursor};
-use crate::doc::Document;
+use std::collections::{HashMap, HashSet};
 use pdf::{PdfWriter, Id, Rect, Version, Trailer};
 use pdf::doc::{Catalog, PageTree, Page, Resource, Content};
 use pdf::text::Text;
@@ -11,6 +11,8 @@ use pdf::font::{
     WidthRecord, FontDescriptor, FontFlags, EmbeddedFont, GlyphUnit
 };
 use opentype::{OpenTypeReader, tables::{self, NameEntry, MacStyleFlags}};
+use crate::doc::Document;
+use crate::font::Font;
 
 
 /// A type that is a sink for documents that can be written in the _PDF_ format.
@@ -47,6 +49,12 @@ impl From<opentype::Error> for PdfWritingError {
     }
 }
 
+impl From<crate::font::SubsettingError> for PdfWritingError {
+    fn from(err: crate::font::SubsettingError) -> PdfWritingError {
+        PdfWritingError { message: format!("{}", err) }
+    }
+}
+
 impl fmt::Display for PdfWritingError {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
         write!(f, "pdf writing error: {}", self.message)
@@ -60,7 +68,7 @@ struct PdfCreator<'a, W: Write> {
     writer: PdfWriter<'a, W>,
     doc: &'a Document,
     offsets: Offsets,
-    font_data: FontData,
+    font: PdfFont,
 }
 
 /// Offsets for the various groups of ids.
@@ -72,17 +80,6 @@ struct Offsets {
     fonts: (Id, Id),
 }
 
-/// The data we need from the font.
-struct FontData {
-    data: Vec<u8>,
-    name: tables::Name,
-    head: tables::Header,
-    post: tables::Post,
-    os2: tables::OS2,
-    hmtx: tables::HorizontalMetrics,
-    cmap: tables::CharMap,
-}
-
 impl<'a, W: Write> PdfCreator<'a, W> {
     /// Create a new _PDF_ Creator.
     pub fn new(target: &'a mut W, doc: &'a Document) -> PdfResult<PdfCreator<'a, W>> {
@@ -94,9 +91,17 @@ impl<'a, W: Write> PdfCreator<'a, W> {
         let contents = (pages.1 + 1, pages.1 + content_count);
         let fonts = (contents.1 + 1, contents.1 + 4);
 
-        // Read the font from a file.
+        // Find out which chars are used in this document.
+        let mut chars = HashSet::new();
+        for page in &doc.pages {
+            for content in &page.contents {
+                chars.extend(content.0.chars());
+            }
+        }
+
+        // Create a subsetted pdf font.
         let data = std::fs::read(format!("../fonts/{}.ttf", doc.font))?;
-        let font_data = FontData::load(data)?;
+        let font = PdfFont::new(&doc.font, data, chars)?;
 
         Ok(PdfCreator {
             writer: PdfWriter::new(target),
@@ -108,7 +113,7 @@ impl<'a, W: Write> PdfCreator<'a, W> {
                 contents,
                 fonts,
             },
-            font_data,
+            font,
         })
     }
 
@@ -184,17 +189,9 @@ impl<'a, W: Write> PdfCreator<'a, W> {
     /// Write the fonts.
     fn write_fonts(&mut self) -> PdfResult<()> {
         let id = self.offsets.fonts.0;
-        let font_data = &self.font_data;
-
-        // Create conversion function from font units to PDF units.
-        let ratio = 1000.0 / (font_data.head.units_per_em as f32);
-        let convert = |x| (ratio * x as f32).round() as GlyphUnit;
-
-        let font_name = font_data.name.get_decoded(NameEntry::PostScriptName);
-        let base_font = font_name.as_ref().unwrap_or(&self.doc.font);
 
         self.writer.write_obj(id, &Type0Font::new(
-            base_font.clone(),
+            self.font.name.clone(),
             CMapEncoding::Predefined("Identity-H".to_owned()),
             id + 1
         )).unwrap();
@@ -202,80 +199,124 @@ impl<'a, W: Write> PdfCreator<'a, W> {
         self.writer.write_obj(id + 1,
             CIDFont::new(
                 CIDFontType::Type2,
-                base_font.clone(),
+                self.font.name.clone(),
                 CIDSystemInfo::new("(Adobe)", "(Identity)", 0),
                 id + 2,
-            ).widths(vec![
-                WidthRecord::start(0, font_data.hmtx.metrics.iter().map(|m| convert(m.advance_width))
-            )])
+            ).widths(vec![WidthRecord::start(0, self.font.widths.clone())])
         ).unwrap();
 
-        let mut flags = FontFlags::empty();
-        flags.set(FontFlags::FIXED_PITCH, font_data.post.is_fixed_pitch);
-        flags.set(FontFlags::SERIF, base_font.contains("Serif"));
-        flags.insert(FontFlags::SYMBOLIC);
-        flags.set(FontFlags::ITALIC, font_data.head.mac_style.contains(MacStyleFlags::ITALIC));
-        flags.insert(FontFlags::SMALL_CAP);
-
         self.writer.write_obj(id + 2,
             FontDescriptor::new(
-                base_font.clone(),
-                flags,
-                font_data.post.italic_angle.to_f32(),
+                self.font.name.clone(),
+                self.font.flags,
+                self.font.italic_angle,
             )
-            .font_bbox(Rect::new(
-                convert(font_data.head.x_min),
-                convert(font_data.head.y_min),
-                convert(font_data.head.x_max),
-                convert(font_data.head.y_max)
-            ))
-            .ascent(convert(font_data.os2.s_typo_ascender))
-            .descent(convert(font_data.os2.s_typo_descender))
-            .cap_height(convert(font_data.os2.s_cap_height
-                .unwrap_or(font_data.os2.s_typo_ascender)))
-            .stem_v((10.0 + 220.0 * (font_data.os2.us_weight_class as f32
-                - 50.0) / 900.0) as GlyphUnit)
+            .font_bbox(self.font.bounding_box)
+            .ascent(self.font.ascender)
+            .descent(self.font.descender)
+            .cap_height(self.font.cap_height)
+            .stem_v(self.font.stem_v)
             .font_file_3(id + 3)
         ).unwrap();
 
-        self.writer.write_obj(id + 3, &EmbeddedFont::OpenType(&font_data.data)).unwrap();
+
+        self.writer.write_obj(id + 3, &EmbeddedFont::OpenType(&self.font.data)).unwrap();
 
         Ok(())
     }
 
     /// Encode the given text for our font.
     fn encode(&self, text: &str) -> Vec<u8> {
-        let default = self.font_data.os2.us_default_char.unwrap_or(0);
         let mut bytes = Vec::with_capacity(2 * text.len());
-        text.chars().map(|c| {
-            self.font_data.cmap.get(c).unwrap_or(default)
-        })
-        .for_each(|glyph| {
+        for glyph in text.chars().map(|c| self.font.map(c)) {
             bytes.push((glyph >> 8) as u8);
             bytes.push((glyph & 0xff) as u8);
-        });
+        }
         bytes
     }
 }
 
-impl FontData {
-    /// Load various needed tables from the font data.
-    pub fn load(data: Vec<u8>) -> PdfResult<FontData> {
-        let mut readable = Cursor::new(data);
+
+/// The data we need from the font.
+struct PdfFont {
+    data: Vec<u8>,
+    mapping: HashMap<char, u16>,
+    default_glyph: u16,
+    name: String,
+    widths: Vec<GlyphUnit>,
+    flags: FontFlags,
+    italic_angle: f32,
+    bounding_box: Rect<GlyphUnit>,
+    ascender: GlyphUnit,
+    descender: GlyphUnit,
+    cap_height: GlyphUnit,
+    stem_v: GlyphUnit,
+}
+
+impl PdfFont {
+    /// Create a subetted version of the font and calculate some information
+    /// needed for creating the _PDF_.
+    pub fn new(font_name: &str, data: Vec<u8>, chars: HashSet<char>) -> PdfResult<PdfFont> {
+        let mut readable = Cursor::new(&data);
         let mut reader = OpenTypeReader::new(&mut readable);
 
-        let name = reader.read_table::<tables::Name>()?;
         let head = reader.read_table::<tables::Header>()?;
+        let name = reader.read_table::<tables::Name>()?;
         let post = reader.read_table::<tables::Post>()?;
         let os2 = reader.read_table::<tables::OS2>()?;
-        let hmtx = reader.read_table::<tables::HorizontalMetrics>()?;
-        let cmap = reader.read_table::<tables::CharMap>()?;
 
-        Ok(FontData {
-            data: readable.into_inner(),
-            name, head, post, os2, hmtx, cmap,
+        let font = Font::new(data);
+        let (subsetted, mapping) = font.subsetted(
+            chars,
+            &["head", "hhea", "maxp", "hmtx", "loca", "glyf"],
+            &["cvt ", "prep", "fpgm", "OS/2", "cmap", "name", "post"],
+        )?;
+
+        let unit_ratio = 1000.0 / (head.units_per_em as f32);
+        let convert = |x| (unit_ratio * x as f32).round() as GlyphUnit;
+
+        let base_font = name.get_decoded(NameEntry::PostScriptName);
+        let font_name =  base_font.unwrap_or_else(|| font_name.to_owned());
+
+
+        let mut flags = FontFlags::empty();
+        flags.set(FontFlags::FIXED_PITCH, post.is_fixed_pitch);
+        flags.set(FontFlags::SERIF, font_name.contains("Serif"));
+        flags.insert(FontFlags::SYMBOLIC);
+        flags.set(FontFlags::ITALIC, head.mac_style.contains(MacStyleFlags::ITALIC));
+        flags.insert(FontFlags::SMALL_CAP);
+
+        let mut readable = Cursor::new(&subsetted);
+        let mut reader = OpenTypeReader::new(&mut readable);
+        let hmtx = reader.read_table::<tables::HorizontalMetrics>()?;
+        let widths = hmtx.metrics.iter().map(|m| convert(m.advance_width)).collect();
+
+
+        Ok(PdfFont {
+            data: subsetted,
+            mapping,
+            default_glyph: os2.us_default_char.unwrap_or(0),
+            name: font_name,
+            widths,
+            flags,
+            italic_angle: post.italic_angle.to_f32(),
+            bounding_box: Rect::new(
+                convert(head.x_min),
+                convert(head.y_min),
+                convert(head.x_max),
+                convert(head.y_max)
+            ),
+            ascender: convert(os2.s_typo_ascender),
+            descender: convert(os2.s_typo_descender),
+            cap_height: convert(os2.s_cap_height.unwrap_or(os2.s_typo_ascender)),
+            stem_v: (10.0 + 220.0 * (os2.us_weight_class as f32 - 50.0) / 900.0) as GlyphUnit,
         })
     }
+
+    /// Map a character to it's glyph index.
+    fn map(&self, c: char) -> u16 {
+        self.mapping.get(&c).map(|&g| g).unwrap_or(self.default_glyph)
+    }
 }
 
 
@@ -304,4 +345,17 @@ mod pdf_tests {
              Stet clita kasd gubergren, no sea takimata sanctus est.
         ");
     }
+
+    // #[test]
+    // fn pdf_fix_1() {
+    //     use unicode_normalization::UnicodeNormalization;
+
+    //     let text = "Hello World! from Typeset‼";
+    //     let chars = text.nfd().collect::<HashSet<char>>();
+
+    //     // Create a subsetted pdf font.
+    //     let data = std::fs::read("../fonts/NotoSans-Regular.ttf").unwrap();
+    //     let font = PdfFont::new("NotoSans-Regular", data, chars).unwrap();
+    //     std::fs::write("../target/NotoTest.ttf", font.data).unwrap();
+    // }
 }