From 1629a7e30c6010812f7412f99ade448f7d0d94df Mon Sep 17 00:00:00 2001
From: Shadowfacts <me@shadowfacts.net>
Date: Tue, 14 Jan 2025 21:23:11 -0500
Subject: [PATCH] Character set extraction

---
 Cargo.lock                          |  19 +-
 Cargo.toml                          |   2 +
 src/generator/archive.rs            |   2 +-
 src/generator/css.rs                |  92 ++++++--
 src/generator/css/character_sets.rs | 322 ++++++++++++++++++++++++++++
 src/generator/css/font_subset.rs    |  46 ++++
 src/generator/home.rs               |   2 +-
 src/generator/mod.rs                |  50 +++--
 src/generator/not_found.rs          |   8 +-
 src/generator/posts.rs              |  14 +-
 src/generator/tags.rs               |  11 +-
 src/generator/templates.rs          |  22 +-
 src/generator/tutorials.rs          |  32 +--
 src/generator/tv.rs                 |  10 +-
 14 files changed, 537 insertions(+), 95 deletions(-)
 create mode 100644 src/generator/css/character_sets.rs
 create mode 100644 src/generator/css/font_subset.rs

diff --git a/Cargo.lock b/Cargo.lock
index 5458bf5..96feda4 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -24,6 +24,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "e89da841a80418a9b391ebaea17f5c112ffaaa96f621d2c285b5174da76b9011"
 dependencies = [
  "cfg-if",
+ "getrandom",
  "once_cell",
  "version_check",
  "zerocopy",
@@ -162,9 +163,9 @@ checksum = "bef38d45163c2f1dde094a7dfd33ccf595c92905c8f8f4fdc18d06fb1037718a"
 
 [[package]]
 name = "bitflags"
-version = "2.6.0"
+version = "2.7.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "b048fb63fd8b5923fc5aa7b340d8e156aec7ec02f0c78fa8a6ddc2613f6f71de"
+checksum = "1be3f42a67d6d345ecd59f675f3f012d6974981560836e938c22b424b85ce1be"
 
 [[package]]
 name = "block-buffer"
@@ -711,7 +712,7 @@ version = "0.9.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "0bf760ebf69878d9fd8f110c89703d90ce35095324d1f1edcb595c63945ee757"
 dependencies = [
- "bitflags 2.6.0",
+ "bitflags 2.7.0",
  "ignore",
  "walkdir",
 ]
@@ -1038,7 +1039,7 @@ version = "0.1.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "c0ff37bd590ca25063e35af745c343cb7a0271906fb7b37e4813e8f79f00268d"
 dependencies = [
- "bitflags 2.6.0",
+ "bitflags 2.7.0",
  "libc",
  "redox_syscall",
 ]
@@ -1152,7 +1153,7 @@ version = "7.0.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "c533b4c39709f9ba5005d8002048266593c1cfaf3c5f0739d5b8ab0c6c504009"
 dependencies = [
- "bitflags 2.6.0",
+ "bitflags 2.7.0",
  "filetime",
  "fsevent-sys",
  "inotify",
@@ -1404,7 +1405,7 @@ version = "0.12.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "f86ba2052aebccc42cbbb3ed234b8b13ce76f75c3551a303cb2bcffcff12bb14"
 dependencies = [
- "bitflags 2.6.0",
+ "bitflags 2.7.0",
  "getopts",
  "memchr",
  "pulldown-cmark-escape",
@@ -1472,7 +1473,7 @@ version = "0.5.8"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "03a862b389f93e68874fbf580b9de08dd02facb9a788ebadaf4a3fd33cf58834"
 dependencies = [
- "bitflags 2.6.0",
+ "bitflags 2.7.0",
 ]
 
 [[package]]
@@ -1933,7 +1934,7 @@ version = "0.6.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "403fa3b783d4b626a8ad51d766ab03cb6d2dbfc46b1c5d4448395e6628dc9697"
 dependencies = [
- "bitflags 2.6.0",
+ "bitflags 2.7.0",
  "bytes",
  "futures-util",
  "http",
@@ -2235,8 +2236,10 @@ checksum = "06abde3611657adf66d383f00b093d7faecc7fa57071cce2578660c9f1010821"
 name = "v7"
 version = "0.1.0"
 dependencies = [
+ "ahash",
  "anyhow",
  "base64",
+ "bitflags 2.7.0",
  "chrono",
  "clap",
  "compute_graph",
diff --git a/Cargo.toml b/Cargo.toml
index 4cdd027..c48a7bd 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -16,8 +16,10 @@ serde = { version = "1.0", features = ["derive"] }
 serde_json = "1.0"
 
 [dependencies]
+ahash = "0.8.11"
 anyhow = "1.0.95"
 base64 = "0.22.1"
+bitflags = "2.7.0"
 chrono = { version = "0.4.39", features = ["serde"] }
 clap = { version = "4.5.23", features = ["cargo"] }
 compute_graph = { path = "crates/compute_graph" }
diff --git a/src/generator/archive.rs b/src/generator/archive.rs
index 88da2ce..1cda671 100644
--- a/src/generator/archive.rs
+++ b/src/generator/archive.rs
@@ -23,7 +23,7 @@ pub fn make_graph(
     posts: Input<Vec<Post<HtmlContent>>>,
     default_template: Input<Templates>,
     watcher: &mut FileWatcher,
-) -> Input<()> {
+) -> Input<String> {
     let entries = builder.add_rule(Entries(posts));
     let posts_by_year = builder.add_rule(PostsByYear(entries));
 
diff --git a/src/generator/css.rs b/src/generator/css.rs
index 279ce89..aa4a108 100644
--- a/src/generator/css.rs
+++ b/src/generator/css.rs
@@ -1,3 +1,6 @@
+mod character_sets;
+mod font_subset;
+
 use std::{
     cell::RefCell,
     collections::{HashMap, HashSet},
@@ -7,10 +10,11 @@ use std::{
 };
 
 use base64::{Engine, prelude::BASE64_STANDARD};
+use character_sets::{CharacterSets, FontKey};
 use compute_graph::{
     InvalidationSignal,
     builder::GraphBuilder,
-    input::{Input, InputVisitable, InputVisitor},
+    input::{DynamicInput, Input, InputVisitable, InputVisitor},
     rule::Rule,
     synchronicity::Asynchronous,
 };
@@ -20,44 +24,67 @@ use log::error;
 
 use super::{
     FileWatcher,
-    util::{content_path, output_writer},
+    util::{Combine, content_path, output_writer},
 };
 
 pub fn make_graph(
     builder: &mut GraphBuilder<(), Asynchronous>,
+    render_inputs: Vec<Input<String>>,
+    render_dynamic_inputs: Vec<DynamicInput<String>>,
     watcher: Rc<RefCell<FileWatcher>>,
 ) -> Input<()> {
     let mut watcher_ = watcher.borrow_mut();
-    let mut files = HashMap::<&'static str, Input<String>>::new();
-    let filenames = [
+    let mut variables = HashMap::<&'static str, Input<String>>::new();
+
+    variables.insert(
+        "external-link",
+        read_to_base64(
+            content_path("css/external-link.svg"),
+            builder,
+            &mut *watcher_,
+        ),
+    );
+
+    let character_sets = character_sets::make_graph(builder, render_inputs, render_dynamic_inputs);
+    let assertion = builder.add_rule(AssertNoBoldMonospace(character_sets.clone()));
+
+    let fonts = [
         (
             "valkyrie-a-regular",
             content_path("css/fonts/valkyrie_a_regular.woff2"),
+            FontKey::empty(),
         ),
         (
             "valkyrie-a-bold",
             content_path("css/fonts/valkyrie_a_bold.woff2"),
+            FontKey::BOLD,
         ),
         (
             "valkyrie-a-italic",
             content_path("css/fonts/valkyrie_a_italic.woff2"),
+            FontKey::ITALIC,
         ),
         (
             "valkyrie-a-bold-italic",
             content_path("css/fonts/valkyrie_a_bold_italic.woff2"),
+            FontKey::BOLD.union(FontKey::ITALIC),
         ),
-        ("external-link", content_path("css/external-link.svg")),
         (
             "berkeley-mono-regular",
             content_path("css/fonts/BerkeleyMono-Regular.woff2"),
+            FontKey::MONOSPACE,
         ),
         (
             "berkeley-mono-italic",
             content_path("css/fonts/BerkeleyMono-Oblique.woff2"),
+            FontKey::MONOSPACE.union(FontKey::ITALIC),
         ),
     ];
-    for (name, path) in filenames.into_iter() {
-        files.insert(name, read_file(path, builder, &mut *watcher_));
+    for (name, path, font_key) in fonts.into_iter() {
+        let file = read_file(path, builder, &mut *watcher_);
+        let subsetted = font_subset::make_graph(builder, file, character_sets.clone(), font_key);
+        let base64 = builder.add_rule(ConvertToBase64(subsetted));
+        variables.insert(name, base64);
     }
     drop(watcher_);
 
@@ -66,31 +93,40 @@ pub fn make_graph(
         watcher,
         watched: HashSet::new(),
         invalidate: Rc::clone(&invalidate_css_box),
-        fonts: files,
+        variables,
     });
     invalidate_css_box.replace(Some(invalidate_css));
-    css
+    builder.add_rule(Combine(css, assertion))
 }
 
 fn read_file(
     path: PathBuf,
     builder: &mut GraphBuilder<(), Asynchronous>,
     watcher: &mut FileWatcher,
-) -> Input<String> {
-    let (font, invalidate) = builder.add_invalidatable_rule(ReadFile(path.clone()));
+) -> Input<Vec<u8>> {
+    let (file, invalidate) = builder.add_invalidatable_rule(ReadFile(path.clone()));
     watcher.watch(path, move || invalidate.invalidate());
-    font
+    file
+}
+
+fn read_to_base64(
+    path: PathBuf,
+    builder: &mut GraphBuilder<(), Asynchronous>,
+    watcher: &mut FileWatcher,
+) -> Input<String> {
+    let file = read_file(path, builder, watcher);
+    builder.add_rule(ConvertToBase64(file))
 }
 
 struct CompileScss {
     watcher: Rc<RefCell<FileWatcher>>,
     watched: HashSet<PathBuf>,
     invalidate: Rc<RefCell<Option<InvalidationSignal>>>,
-    fonts: HashMap<&'static str, Input<String>>,
+    variables: HashMap<&'static str, Input<String>>,
 }
 impl InputVisitable for CompileScss {
     fn visit_inputs(&self, visitor: &mut impl InputVisitor) {
-        for input in self.fonts.values() {
+        for input in self.variables.values() {
             visitor.visit(input);
         }
     }
@@ -106,7 +142,7 @@ impl Rule for CompileScss {
             OutputStyle::Compressed
         };
         let mut options = Options::default().fs(&fs).style(style);
-        for (name, input) in self.fonts.iter() {
+        for (name, input) in self.variables.iter() {
             let value = Value::String(input.value().to_owned(), QuoteKind::None);
             options = options.add_custom_var(*name, value);
         }
@@ -160,14 +196,14 @@ impl<'a> Fs for TrackingFs<'a> {
 #[derive(InputVisitable)]
 struct ReadFile(#[skip_visit] PathBuf);
 impl Rule for ReadFile {
-    type Output = String;
+    type Output = Vec<u8>;
 
     fn evaluate(&mut self) -> Self::Output {
         match std::fs::read(&self.0) {
-            Ok(data) => BASE64_STANDARD.encode(data),
+            Ok(data) => data,
             Err(e) => {
                 error!("Error reading font {:?}: {:?}", &self.0, e);
-                String::new()
+                vec![]
             }
         }
     }
@@ -176,3 +212,23 @@ impl Rule for ReadFile {
         write!(f, "{}", self.0.display())
     }
 }
+
+#[derive(InputVisitable)]
+struct ConvertToBase64(Input<Vec<u8>>);
+impl Rule for ConvertToBase64 {
+    type Output = String;
+    fn evaluate(&mut self) -> Self::Output {
+        BASE64_STANDARD.encode(self.input_0().as_slice())
+    }
+}
+
+#[derive(InputVisitable)]
+struct AssertNoBoldMonospace(Input<CharacterSets>);
+impl Rule for AssertNoBoldMonospace {
+    type Output = ();
+    fn evaluate(&mut self) -> Self::Output {
+        let sets = self.input_0();
+        assert!(sets.bold_monospace().is_empty());
+        assert!(sets.bold_italic_monospace().is_empty());
+    }
+}
diff --git a/src/generator/css/character_sets.rs b/src/generator/css/character_sets.rs
new file mode 100644
index 0000000..0befa6f
--- /dev/null
+++ b/src/generator/css/character_sets.rs
@@ -0,0 +1,322 @@
+use bitflags::bitflags;
+use compute_graph::{
+    NodeId,
+    builder::GraphBuilder,
+    input::{DynamicInput, Input, InputVisitable},
+    rule::{DynamicNodeFactory, DynamicRule, DynamicRuleContext, Rule},
+    synchronicity::Asynchronous,
+};
+use html5ever::{
+    Attribute, local_name,
+    tokenizer::{
+        BufferQueue, TagKind, Token, TokenSink, TokenSinkResult, Tokenizer, TokenizerOpts,
+        TokenizerResult,
+    },
+};
+
+pub fn make_graph(
+    builder: &mut GraphBuilder<(), Asynchronous>,
+    inputs: Vec<Input<String>>,
+    dynamic_inputs: Vec<DynamicInput<String>>,
+) -> Input<CharacterSets> {
+    let mut charsets = inputs
+        .into_iter()
+        .map(|inp| builder.add_rule(BuildCharacterSet(inp)))
+        .collect::<Vec<_>>();
+    let dynamic_charsets =
+        builder.add_dynamic_rule(MakeBuildDynamicCharacterSets::new(dynamic_inputs));
+    let dynamic_unioned = builder.add_rule(UnionDynamicCharacterSets(dynamic_charsets));
+    charsets.push(dynamic_unioned);
+    builder.add_rule(UnionCharacterSets(charsets))
+}
+
+#[derive(InputVisitable)]
+struct BuildCharacterSet(Input<String>);
+impl Rule for BuildCharacterSet {
+    type Output = CharacterSets;
+    fn evaluate(&mut self) -> Self::Output {
+        get_character_sets(&*self.input_0())
+    }
+}
+
+struct MakeBuildDynamicCharacterSets {
+    strings: Vec<DynamicInput<String>>,
+    factory: DynamicNodeFactory<NodeId, CharacterSets>,
+}
+impl MakeBuildDynamicCharacterSets {
+    fn new(strings: Vec<DynamicInput<String>>) -> Self {
+        Self {
+            strings,
+            factory: DynamicNodeFactory::new(),
+        }
+    }
+}
+impl InputVisitable for MakeBuildDynamicCharacterSets {
+    fn visit_inputs(&self, visitor: &mut impl compute_graph::input::InputVisitor) {
+        for input in self.strings.iter() {
+            input.visit_inputs(visitor);
+        }
+    }
+}
+impl DynamicRule for MakeBuildDynamicCharacterSets {
+    type ChildOutput = CharacterSets;
+    fn evaluate(&mut self, ctx: &mut impl DynamicRuleContext) -> Vec<Input<Self::ChildOutput>> {
+        for dynamic_input in self.strings.iter() {
+            for input in dynamic_input.value().inputs.iter() {
+                self.factory.add_node(ctx, input.node_id(), |ctx| {
+                    ctx.add_rule(BuildCharacterSet(input.clone()))
+                });
+            }
+        }
+        self.factory.all_nodes(ctx)
+    }
+}
+
+struct UnionCharacterSets(Vec<Input<CharacterSets>>);
+impl InputVisitable for UnionCharacterSets {
+    fn visit_inputs(&self, visitor: &mut impl compute_graph::input::InputVisitor) {
+        for input in self.0.iter() {
+            input.visit_inputs(visitor);
+        }
+    }
+}
+impl Rule for UnionCharacterSets {
+    type Output = CharacterSets;
+    fn evaluate(&mut self) -> Self::Output {
+        let mut merged = CharacterSets::default();
+        for input in self.0.iter() {
+            merged.extend(&*input.value());
+        }
+        merged
+    }
+}
+
+#[derive(InputVisitable)]
+struct UnionDynamicCharacterSets(DynamicInput<CharacterSets>);
+impl Rule for UnionDynamicCharacterSets {
+    type Output = CharacterSets;
+    fn evaluate(&mut self) -> Self::Output {
+        let mut merged = CharacterSets::default();
+        for input in self.0.value().inputs.iter() {
+            merged.extend(&*input.value());
+        }
+        merged
+    }
+}
+
+fn get_character_sets(html: &str) -> CharacterSets {
+    let accumulator = CharacterSetAccumulator::default();
+    let mut tokenizer = Tokenizer::new(accumulator, TokenizerOpts::default());
+    let mut queue = BufferQueue::default();
+    queue.push_back(html.into());
+    let result = tokenizer.feed(&mut queue);
+    match result {
+        TokenizerResult::Done => (),
+        result => panic!("unexpected result: {result:?}"),
+    }
+    tokenizer.sink.characters
+}
+
+#[derive(Default, PartialEq, Clone)]
+pub struct CharacterSets {
+    sets: [ahash::HashSet<char>; FONT_VARIATIONS],
+}
+impl CharacterSets {
+    pub fn get(&self, key: FontKey) -> &ahash::HashSet<char> {
+        &self.sets[key.bits() as usize]
+    }
+
+    pub fn get_mut(&mut self, key: FontKey) -> &mut ahash::HashSet<char> {
+        &mut self.sets[key.bits() as usize]
+    }
+
+    fn extend(&mut self, other: &CharacterSets) {
+        for i in 0..FONT_VARIATIONS {
+            self.sets[i].extend(&other.sets[i]);
+        }
+    }
+}
+
+#[allow(unused)]
+impl CharacterSets {
+    pub fn regular(&self) -> &ahash::HashSet<char> {
+        &self.sets[0]
+    }
+
+    pub fn bold(&self) -> &ahash::HashSet<char> {
+        self.get(FontKey::BOLD)
+    }
+
+    pub fn italic(&self) -> &ahash::HashSet<char> {
+        self.get(FontKey::ITALIC)
+    }
+
+    pub fn monospace(&self) -> &ahash::HashSet<char> {
+        self.get(FontKey::MONOSPACE)
+    }
+
+    pub fn bold_italic(&self) -> &ahash::HashSet<char> {
+        self.get(FontKey::BOLD.union(FontKey::ITALIC))
+    }
+
+    pub fn bold_monospace(&self) -> &ahash::HashSet<char> {
+        self.get(FontKey::BOLD.union(FontKey::MONOSPACE))
+    }
+
+    pub fn italic_monospace(&self) -> &ahash::HashSet<char> {
+        self.get(FontKey::ITALIC.union(FontKey::MONOSPACE))
+    }
+
+    pub fn bold_italic_monospace(&self) -> &ahash::HashSet<char> {
+        self.get(FontKey::all())
+    }
+}
+impl std::fmt::Debug for CharacterSets {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        let keys = [
+            (FontKey::empty(), "regular"),
+            (FontKey::BOLD, "bold"),
+            (FontKey::ITALIC, "italic"),
+            (FontKey::MONOSPACE, "monospace"),
+            (FontKey::BOLD.union(FontKey::ITALIC), "bold_italic"),
+            (FontKey::BOLD.union(FontKey::MONOSPACE), "bold_monospace"),
+            (
+                FontKey::ITALIC.union(FontKey::MONOSPACE),
+                "italic_monospace",
+            ),
+            (FontKey::all(), "bold_italic_monospace"),
+        ];
+        let mut debug = f.debug_struct("CharacterSets");
+        let mut had_empty = false;
+        for (key, name) in keys {
+            let chars = self.get(key);
+            if chars.is_empty() {
+                had_empty = true;
+            } else {
+                debug.field(name, chars);
+            }
+        }
+        if had_empty {
+            debug.finish_non_exhaustive()
+        } else {
+            debug.finish()
+        }
+    }
+}
+
+bitflags! {
+    #[derive(Clone, Copy)]
+    pub struct FontKey: u8 {
+        const BOLD = 1;
+        const ITALIC = 1 << 1;
+        const MONOSPACE = 1 << 2;
+    }
+}
+
+const FONT_VARIATIONS: usize = FontKey::all().bits() as usize + 1;
+
+// N.B.: html5ever 0.28.0 changed TokenSink::process_token to take &self.
+// At which point we upgrade, the state on this type will need to use something
+// else to provide interior mutability.
+#[derive(Default)]
+struct CharacterSetAccumulator {
+    characters: CharacterSets,
+    depths: [usize; 3],
+}
+impl CharacterSetAccumulator {
+    fn handle_token(&mut self, token: Token) {
+        match token {
+            Token::TagToken(tag) => {
+                let depth = if tag.name == local_name!("strong") || tag.name == local_name!("b") {
+                    &mut self.depths[0]
+                } else if tag.name == local_name!("em")
+                    || tag.name == local_name!("i")
+                    || tag.attrs.iter().any(Self::is_hl_cmt)
+                {
+                    &mut self.depths[1]
+                } else if tag.name == local_name!("code") {
+                    &mut self.depths[2]
+                } else {
+                    return;
+                };
+                if tag.kind == TagKind::StartTag {
+                    *depth += 1;
+                } else {
+                    *depth -= 1;
+                }
+            }
+            Token::CharacterTokens(s) => {
+                let mut key = FontKey::empty();
+                key.set(FontKey::BOLD, self.depths[0] > 0);
+                key.set(FontKey::ITALIC, self.depths[1] > 0);
+                key.set(FontKey::MONOSPACE, self.depths[2] > 0);
+                let set = self.characters.get_mut(key);
+                set.extend(s.chars());
+            }
+            _ => (),
+        }
+    }
+
+    fn is_hl_cmt(attr: &Attribute) -> bool {
+        attr.name.prefix == None
+            && attr.name.local == local_name!("class")
+            // this is a bit of a kludge for performance; the hl-cmt class is only
+            // ever used by itself, so we don't try to parse the attr value
+            && attr.value == "hl-cmt".into()
+    }
+}
+impl TokenSink for CharacterSetAccumulator {
+    type Handle = ();
+    fn process_token(&mut self, token: Token, _line_number: u64) -> TokenSinkResult<Self::Handle> {
+        self.handle_token(token);
+        TokenSinkResult::Continue
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::get_character_sets;
+
+    macro_rules! char_set {
+        ($s:ident) => {
+            stringify!($s).chars().collect::<ahash::HashSet<char>>()
+        };
+    }
+
+    #[test]
+    fn simple() {
+        let result = get_character_sets("<p>test</p>");
+        assert!(result.bold().is_empty());
+        assert!(result.italic().is_empty());
+        assert!(result.monospace().is_empty());
+        assert!(result.regular() == &char_set!(tes));
+    }
+
+    #[test]
+    fn formatting() {
+        let result = get_character_sets("<p>te<strong>st</strong></p>");
+        assert!(result.bold() == &char_set!(st));
+        assert!(result.italic().is_empty());
+        assert!(result.monospace().is_empty());
+        assert!(result.regular() == &char_set!(te));
+    }
+
+    #[test]
+    fn combined_formatting() {
+        let result = get_character_sets("<strong>a<em>b</em></strong>");
+        assert!(result.bold() == &char_set!(a));
+        assert!(result.bold_italic() == &char_set!(b));
+    }
+
+    #[test]
+    fn redundant_nesting() {
+        let result = get_character_sets("<b><b>x</b>y</b>");
+        assert!(result.bold() == &char_set!(xy));
+    }
+
+    #[test]
+    fn hl_cmt_is_italic() {
+        let result = get_character_sets(r#"<span class="hl-cmt">a</span>"#);
+        assert!(result.italic() == &char_set!(a));
+    }
+}
diff --git a/src/generator/css/font_subset.rs b/src/generator/css/font_subset.rs
new file mode 100644
index 0000000..37ac8ee
--- /dev/null
+++ b/src/generator/css/font_subset.rs
@@ -0,0 +1,46 @@
+use compute_graph::{
+    builder::GraphBuilder,
+    input::{Input, InputVisitable},
+    rule::Rule,
+    synchronicity::Asynchronous,
+};
+
+use super::character_sets::{CharacterSets, FontKey};
+
+pub fn make_graph(
+    builder: &mut GraphBuilder<(), Asynchronous>,
+    font: Input<Vec<u8>>,
+    character_sets: Input<CharacterSets>,
+    key: FontKey,
+) -> Input<Vec<u8>> {
+    let characters = builder.add_rule(GetCharacterSet {
+        sets: character_sets,
+        key,
+    });
+    builder.add_rule(SubsetFont { font, characters })
+}
+
+#[derive(InputVisitable)]
+struct GetCharacterSet {
+    sets: Input<CharacterSets>,
+    #[skip_visit]
+    key: FontKey,
+}
+impl Rule for GetCharacterSet {
+    type Output = ahash::HashSet<char>;
+    fn evaluate(&mut self) -> Self::Output {
+        self.sets().get(self.key).clone()
+    }
+}
+
+#[derive(InputVisitable)]
+struct SubsetFont {
+    font: Input<Vec<u8>>,
+    characters: Input<ahash::HashSet<char>>,
+}
+impl Rule for SubsetFont {
+    type Output = Vec<u8>;
+    fn evaluate(&mut self) -> Self::Output {
+        self.font().clone()
+    }
+}
diff --git a/src/generator/home.rs b/src/generator/home.rs
index 0f2f897..d833466 100644
--- a/src/generator/home.rs
+++ b/src/generator/home.rs
@@ -21,7 +21,7 @@ pub fn make_graph(
     posts: Input<Vec<Post<HtmlContent>>>,
     default_template: Input<Templates>,
     watcher: &mut FileWatcher,
-) -> Input<()> {
+) -> Input<String> {
     let latest_post = builder.add_rule(LatestPost(posts));
 
     let template_path = content_path("index.html");
diff --git a/src/generator/mod.rs b/src/generator/mod.rs
index bb0fa45..e76ad7a 100644
--- a/src/generator/mod.rs
+++ b/src/generator/mod.rs
@@ -15,6 +15,7 @@ mod util;
 use std::cell::RefCell;
 use std::rc::Rc;
 
+use compute_graph::input::{DynamicInput, Input};
 use compute_graph::{AsyncGraph, builder::GraphBuilder};
 use util::Combine;
 
@@ -34,64 +35,71 @@ pub async fn generate(watcher: Rc<RefCell<FileWatcher>>) -> anyhow::Result<Async
 fn make_graph(watcher: Rc<RefCell<FileWatcher>>) -> anyhow::Result<AsyncGraph<()>> {
     let mut builder = GraphBuilder::new_async();
 
+    let mut render_inputs: Vec<Input<String>> = vec![];
+    let mut render_dynamic_inputs: Vec<DynamicInput<String>> = vec![];
+
     let default_template = templates::make_graph(&mut builder, &mut *watcher.borrow_mut());
 
-    let (void_outputs, posts, all_posts) =
+    let (render_posts, posts, all_posts) =
         posts::make_graph(&mut builder, default_template.clone(), Rc::clone(&watcher));
+    render_dynamic_inputs.push(render_posts);
 
-    let archive = archive::make_graph(
+    let render_archive = archive::make_graph(
         &mut builder,
         all_posts.clone(),
         default_template.clone(),
         &mut *watcher.borrow_mut(),
     );
+    render_inputs.push(render_archive);
 
-    let tags = tags::make_graph(
+    let render_tags = tags::make_graph(
         &mut builder,
         posts.clone(),
         default_template.clone(),
         &mut *watcher.borrow_mut(),
     );
+    render_dynamic_inputs.push(render_tags);
 
-    let home = home::make_graph(
+    let render_home = home::make_graph(
         &mut builder,
         all_posts,
         default_template.clone(),
         &mut *watcher.borrow_mut(),
     );
-
-    let css = css::make_graph(&mut builder, Rc::clone(&watcher));
+    render_inputs.push(render_home);
 
     let statics = static_files::make_graph(&mut builder, Rc::clone(&watcher));
 
     let rss = rss::make_graph(&mut builder, posts);
 
-    let tv = tv::make_graph(&mut builder, default_template.clone(), Rc::clone(&watcher));
+    let (render_tv_series, render_tv) =
+        tv::make_graph(&mut builder, default_template.clone(), Rc::clone(&watcher));
+    render_dynamic_inputs.push(render_tv_series);
+    render_inputs.push(render_tv);
 
-    let tutorials = tutorials::make_graph(
+    let (render_tutorial_indexes, render_tutorials) = tutorials::make_graph(
         &mut builder,
         default_template.clone(),
         &mut *watcher.borrow_mut(),
     );
+    render_inputs.extend(render_tutorial_indexes);
+    render_dynamic_inputs.extend(render_tutorials);
 
-    let not_found = not_found::make_graph(
+    let render_not_found = not_found::make_graph(
         &mut builder,
         default_template.clone(),
         &mut *watcher.borrow_mut(),
     );
+    render_inputs.push(render_not_found);
 
-    let output = Combine::make(&mut builder, &[
-        void_outputs,
-        archive,
-        tags,
-        home,
-        css,
-        statics,
-        rss,
-        tv,
-        tutorials,
-        not_found,
-    ]);
+    let css = css::make_graph(
+        &mut builder,
+        render_inputs,
+        render_dynamic_inputs,
+        Rc::clone(&watcher),
+    );
+
+    let output = Combine::make(&mut builder, &[css, statics, rss]);
     builder.set_existing_output(output);
     Ok(builder.build()?)
 }
diff --git a/src/generator/not_found.rs b/src/generator/not_found.rs
index 215f56d..525beb4 100644
--- a/src/generator/not_found.rs
+++ b/src/generator/not_found.rs
@@ -14,18 +14,16 @@ pub fn make_graph(
     builder: &mut GraphBuilder<(), Asynchronous>,
     default_template: Input<Templates>,
     watcher: &mut FileWatcher,
-) -> Input<()> {
+) -> Input<String> {
     let path = content_path("404.html");
     let (templates, invalidate) =
         builder.add_invalidatable_rule(AddTemplate::new("404", path.clone(), default_template));
     watcher.watch(path, move || invalidate.invalidate());
 
-    let render = builder.add_rule(RenderTemplate {
+    builder.add_rule(RenderTemplate {
         name: "404",
         output_path: "404.html".into(),
         templates,
         context: make_template_context(&"/404.html".into()).into(),
-    });
-
-    render
+    })
 }
diff --git a/src/generator/posts.rs b/src/generator/posts.rs
index 07342ae..6ab8dc3 100644
--- a/src/generator/posts.rs
+++ b/src/generator/posts.rs
@@ -21,7 +21,7 @@ use tera::Context;
 use super::{
     FileWatcher,
     templates::{AddTemplate, BuildTemplateContext, RenderTemplate, Templates},
-    util::{MapDynamicToVoid, content_path},
+    util::content_path,
 };
 
 pub fn make_graph(
@@ -29,7 +29,7 @@ pub fn make_graph(
     default_template: Input<Templates>,
     watcher: Rc<RefCell<FileWatcher>>,
 ) -> (
-    Input<()>,
+    DynamicInput<String>,
     DynamicInput<ReadPostOutput>,
     Input<Vec<Post<HtmlContent>>>,
 ) {
@@ -57,11 +57,7 @@ pub fn make_graph(
     let write_posts =
         builder.add_dynamic_rule(MakeWritePosts::new(html_posts.clone(), article_template));
 
-    (
-        builder.add_rule(MapDynamicToVoid(write_posts)),
-        posts,
-        builder.add_rule(AllPosts(html_posts)),
-    )
+    (write_posts, posts, builder.add_rule(AllPosts(html_posts)))
 }
 
 #[derive(InputVisitable)]
@@ -264,7 +260,7 @@ struct MakeWritePosts {
     permalink_factory: DynamicNodeFactory<PathBuf, String>,
     output_path_factory: DynamicNodeFactory<PathBuf, PathBuf>,
     build_context_factory: DynamicNodeFactory<PathBuf, Context>,
-    render_factory: DynamicNodeFactory<PathBuf, ()>,
+    render_factory: DynamicNodeFactory<PathBuf, String>,
 }
 impl MakeWritePosts {
     fn new(posts: DynamicInput<Option<Post<HtmlContent>>>, templates: Input<Templates>) -> Self {
@@ -279,7 +275,7 @@ impl MakeWritePosts {
     }
 }
 impl DynamicRule for MakeWritePosts {
-    type ChildOutput = ();
+    type ChildOutput = String;
     fn evaluate(&mut self, ctx: &mut impl DynamicRuleContext) -> Vec<Input<Self::ChildOutput>> {
         for post_input in self.posts.value().inputs.iter() {
             if let Some(post) = post_input.value().as_ref() {
diff --git a/src/generator/tags.rs b/src/generator/tags.rs
index f31a360..00f6d8c 100644
--- a/src/generator/tags.rs
+++ b/src/generator/tags.rs
@@ -16,7 +16,7 @@ use super::{
     archive::{Entry, PostsYearMap},
     posts::{ReadPostOutput, metadata::Tag},
     templates::{AddTemplate, BuildTemplateContext, RenderTemplate, Templates},
-    util::{MapDynamicToVoid, content_path},
+    util::content_path,
 };
 
 pub fn make_graph(
@@ -24,7 +24,7 @@ pub fn make_graph(
     posts: DynamicInput<ReadPostOutput>,
     default_template: Input<Templates>,
     watcher: &mut FileWatcher,
-) -> Input<()> {
+) -> DynamicInput<String> {
     let by_tags = builder.add_dynamic_rule(MakePostsByTags::new(posts));
 
     let template_path = content_path("layout/tag.html");
@@ -35,8 +35,7 @@ pub fn make_graph(
     ));
     watcher.watch(template_path, move || invalidate_template.invalidate());
 
-    let write_tags = builder.add_dynamic_rule(MakeWriteTagPages::new(by_tags, tag_template));
-    builder.add_rule(MapDynamicToVoid(write_tags))
+    builder.add_dynamic_rule(MakeWriteTagPages::new(by_tags, tag_template))
 }
 
 #[derive(InputVisitable)]
@@ -170,7 +169,7 @@ struct MakeWriteTagPages {
     #[skip_visit]
     templates: Input<Templates>,
     build_context_factory: DynamicNodeFactory<String, Context>,
-    render_factory: DynamicNodeFactory<String, ()>,
+    render_factory: DynamicNodeFactory<String, String>,
 }
 impl MakeWriteTagPages {
     fn new(tags: DynamicInput<TagAndPosts>, templates: Input<Templates>) -> Self {
@@ -183,7 +182,7 @@ impl MakeWriteTagPages {
     }
 }
 impl DynamicRule for MakeWriteTagPages {
-    type ChildOutput = ();
+    type ChildOutput = String;
     fn evaluate(
         &mut self,
         ctx: &mut impl compute_graph::rule::DynamicRuleContext,
diff --git a/src/generator/templates.rs b/src/generator/templates.rs
index 1870f0f..5ff24e3 100644
--- a/src/generator/templates.rs
+++ b/src/generator/templates.rs
@@ -1,4 +1,5 @@
 use std::{
+    io::Write,
     path::{Path, PathBuf},
     time::SystemTime,
 };
@@ -178,27 +179,36 @@ pub struct RenderTemplate {
     pub context: RenderTemplateContext,
 }
 impl Rule for RenderTemplate {
-    type Output = ();
+    type Output = String;
 
     fn evaluate(&mut self) -> Self::Output {
         let templates = self.templates.value();
         let has_template = templates.tera.get_template_names().any(|n| n == self.name);
         if !has_template {
             error!("Missing template {:?}", self.name);
-            return;
+            return String::new();
         }
         let path: &Path = match self.output_path {
             TemplateOutputPath::Constant(ref p) => p,
             TemplateOutputPath::Dynamic(ref input) => &input.value(),
         };
-        let writer = output_writer(path).expect("output writer");
+        let mut writer = output_writer(path).expect("output writer");
         let context = match self.context {
             RenderTemplateContext::Constant(ref ctx) => ctx,
             RenderTemplateContext::Dynamic(ref input) => &input.value(),
         };
-        let result = templates.tera.render_to(&self.name, context, writer);
-        if let Err(e) = result {
-            error!("Error rendering template to {path:?}: {e:?}");
+        match templates.tera.render(&self.name, context) {
+            Ok(str) => {
+                let result = writer.write_all(str.as_bytes());
+                if let Err(e) = result {
+                    error!("Error writing template to {path:?}: {e:?}");
+                }
+                str
+            }
+            Err(e) => {
+                error!("Error rendering template {:?}: {:?}", self.name, e);
+                return String::new();
+            }
         }
     }
 
diff --git a/src/generator/tutorials.rs b/src/generator/tutorials.rs
index 10de2e2..b22f332 100644
--- a/src/generator/tutorials.rs
+++ b/src/generator/tutorials.rs
@@ -1,11 +1,11 @@
 use chrono::{DateTime, FixedOffset};
-use compute_graph::input::InputVisitable;
+use compute_graph::input::{DynamicInput, InputVisitable};
 use compute_graph::rule::{DynamicNodeFactory, DynamicRule, DynamicRuleContext};
 use compute_graph::{builder::GraphBuilder, input::Input, synchronicity::Asynchronous};
 use serde::{Deserialize, Serialize};
 
 use crate::generator::templates::{AddTemplate, RenderTemplate, make_template_context};
-use crate::generator::util::{Combine, MapDynamicToVoid, word_count};
+use crate::generator::util::word_count;
 
 use super::markdown;
 use super::util::slugify::slugify;
@@ -16,7 +16,7 @@ pub fn make_graph(
     builder: &mut GraphBuilder<(), Asynchronous>,
     default_template: Input<Templates>,
     watcher: &mut FileWatcher,
-) -> Input<()> {
+) -> (Vec<Input<String>>, Vec<DynamicInput<String>>) {
     let post_path = content_path("layout/tutorial_post.html");
     let (post_template, invalidate) = builder.add_invalidatable_rule(AddTemplate::new(
         "tutorial_post",
@@ -45,10 +45,14 @@ pub fn make_graph(
         read_series("forge-modding-1102", "Forge Mods for 1.10.2"),
         read_series("forge-modding-1112", "Forge Mods for 1.11.2"),
         read_series("forge-modding-112", "Forge Mods for 1.12"),
-    ];
+    ]
+    .into_iter()
+    .flatten()
+    .collect::<Vec<_>>();
 
     let mut index_entries = vec![];
-    let mut render_inputs = vec![];
+    let mut render_series = vec![];
+    let mut render_posts = vec![];
 
     for series in serieses {
         index_entries.push(TutorialIndexEntry {
@@ -73,7 +77,7 @@ pub fn make_graph(
         series_context.insert("entries", &entries);
         series_context.insert("series_name", series.name);
         series_context.insert("series_slug", series.slug);
-        render_inputs.push(builder.add_rule(RenderTemplate {
+        render_series.push(builder.add_rule(RenderTemplate {
             name: "tutorial_series",
             output_path: format!("tutorials/{}/index.html", series.slug).into(),
             templates: series_template.clone(),
@@ -84,25 +88,25 @@ pub fn make_graph(
             series.posts,
             post_template.clone(),
         ));
-        render_inputs.push(builder.add_rule(MapDynamicToVoid(render_dynamic)))
+        render_posts.push(render_dynamic)
     }
 
     let mut index_context = make_template_context(&"/tutorials/".into());
     index_context.insert("entries", &index_entries);
-    render_inputs.push(builder.add_rule(RenderTemplate {
+    render_series.push(builder.add_rule(RenderTemplate {
         name: "tutorials",
         output_path: "tutorials/index.html".into(),
         templates: index_template,
         context: index_context.into(),
     }));
 
-    Combine::make(builder, &render_inputs)
+    (render_series, render_posts)
 }
 
-fn read_series(slug: &'static str, name: &'static str) -> TutorialSeries {
+fn read_series(slug: &'static str, name: &'static str) -> Option<TutorialSeries> {
     let mut path = content_path("tutorials");
     path.push(slug);
-    let entries = std::fs::read_dir(path).expect("reading tutorial dir");
+    let entries = std::fs::read_dir(path).ok()?;
     let posts = entries
         .into_iter()
         .map(move |ent| {
@@ -119,7 +123,7 @@ fn read_series(slug: &'static str, name: &'static str) -> TutorialSeries {
         })
         .collect();
 
-    TutorialSeries { name, slug, posts }
+    Some(TutorialSeries { name, slug, posts })
 }
 
 struct TutorialSeries {
@@ -179,7 +183,7 @@ struct MakeRenderTutorials {
     templates: Input<Templates>,
     #[skip_visit]
     evaluated: bool,
-    render_factory: DynamicNodeFactory<String, ()>,
+    render_factory: DynamicNodeFactory<String, String>,
 }
 impl MakeRenderTutorials {
     fn new(posts: Vec<TutorialPost>, templates: Input<Templates>) -> Self {
@@ -192,7 +196,7 @@ impl MakeRenderTutorials {
     }
 }
 impl DynamicRule for MakeRenderTutorials {
-    type ChildOutput = ();
+    type ChildOutput = String;
     fn evaluate(&mut self, ctx: &mut impl DynamicRuleContext) -> Vec<Input<Self::ChildOutput>> {
         assert!(!self.evaluated);
         self.evaluated = true;
diff --git a/src/generator/tv.rs b/src/generator/tv.rs
index 6be5814..cdcc58a 100644
--- a/src/generator/tv.rs
+++ b/src/generator/tv.rs
@@ -27,14 +27,13 @@ use crate::generator::{
 use super::{
     FileWatcher, markdown,
     templates::{BuildTemplateContext, RenderTemplate, Templates},
-    util::{Combine, MapDynamicToVoid},
 };
 
 pub fn make_graph(
     builder: &mut GraphBuilder<(), Asynchronous>,
     default_template: Input<Templates>,
     watcher: Rc<RefCell<FileWatcher>>,
-) -> Input<()> {
+) -> (DynamicInput<String>, Input<String>) {
     let tv_path = content_path("tv/");
     let (shows, invalidate) = builder
         .add_invalidatable_dynamic_rule(MakeReadShows::new(tv_path.clone(), Rc::clone(&watcher)));
@@ -53,7 +52,6 @@ pub fn make_graph(
         .watch(show_path, move || invalidate.invalidate());
 
     let render_shows = builder.add_dynamic_rule(MakeRenderShows::new(shows.clone(), show_template));
-    let void_outputs = builder.add_rule(MapDynamicToVoid(render_shows));
 
     let tv_path = content_path("tv.html");
     let (index_template, invalidate) =
@@ -78,7 +76,7 @@ pub fn make_graph(
         context: index_context.into(),
     });
 
-    builder.add_rule(Combine(void_outputs, render_index))
+    (render_shows, render_index)
 }
 
 #[derive(InputVisitable)]
@@ -274,7 +272,7 @@ struct MakeRenderShows {
     #[skip_visit]
     templates: Input<Templates>,
     build_context_factory: DynamicNodeFactory<String, Context>,
-    render_factory: DynamicNodeFactory<String, ()>,
+    render_factory: DynamicNodeFactory<String, String>,
 }
 impl MakeRenderShows {
     fn new(shows: DynamicInput<Option<Show>>, templates: Input<Templates>) -> Self {
@@ -287,7 +285,7 @@ impl MakeRenderShows {
     }
 }
 impl DynamicRule for MakeRenderShows {
-    type ChildOutput = ();
+    type ChildOutput = String;
     fn evaluate(&mut self, ctx: &mut impl DynamicRuleContext) -> Vec<Input<Self::ChildOutput>> {
         for show_input in self.shows.value().inputs.iter() {
             if let Some(show) = show_input.value().as_ref() {