Phase 10: Monitoring and automated benchmarks

10.1: Add Criterion dev-dependency and benchmarks for:
  - matching_rules (100 rules)
  - ComputedStyle::compute (empty, 5 props)
  - resolve_string (no vars, 1 var, 3 vars)

10.3: Add --perf CLI flag and src/perf.rs module:
  - PerfScope drop-guard timed scopes (vdom, style, render)
  - Instrumented: VDOM eval (app.rs update), render (app.rs view),
    style matching (style.rs compute_cached)
  - Per-frame report printed to stderr at end of view()

10.2+10.4: Threshold check in perf report:
  - Prints warning if total > 16ms (60 FPS frame budget)

Refactor: Move Message enum to lib.rs so benchmarks can import
the public API. Added lib.rs as library root.

Cargo.lock

@@ -108,6 +108,12 @@ dependencies = [
  "libc",
 ]
 
+[[package]]
+name = "anes"
+version = "0.1.6"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "4b46cbb362ab8752921c97e041f5e366ee6297bd428a31275b9fcf1e380f7299"
+
 [[package]]
 name = "anstream"
 version = "1.0.0"
@@ -583,6 +589,12 @@ dependencies = [
  "wayland-client",
 ]
 
+[[package]]
+name = "cast"
+version = "0.3.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "37b2a672a2cb129a2e41c10b1224bb368f9f37a2b16b612598138befd7b37eb5"
+
 [[package]]
 name = "castaway"
 version = "0.2.4"
@@ -629,6 +641,33 @@ dependencies = [
  "windows-link",
 ]
 
+[[package]]
+name = "ciborium"
+version = "0.2.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "42e69ffd6f0917f5c029256a24d0161db17cea3997d185db0d35926308770f0e"
+dependencies = [
+ "ciborium-io",
+ "ciborium-ll",
+ "serde",
+]
+
+[[package]]
+name = "ciborium-io"
+version = "0.2.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "05afea1e0a06c9be33d539b876f1ce3692f4afea2cb41f740e7743225ed1c757"
+
+[[package]]
+name = "ciborium-ll"
+version = "0.2.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "57663b653d948a338bfb3eeba9bb2fd5fcfaecb9e199e87e1eda4d9e8b240fd9"
+dependencies = [
+ "ciborium-io",
+ "half",
+]
+
 [[package]]
 name = "clap"
 version = "4.6.1"
@@ -910,6 +949,42 @@ dependencies = [
  "cfg-if",
 ]
 
+[[package]]
+name = "criterion"
+version = "0.5.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "f2b12d017a929603d80db1831cd3a24082f8137ce19c69e6447f54f5fc8d692f"
+dependencies = [
+ "anes",
+ "cast",
+ "ciborium",
+ "clap",
+ "criterion-plot",
+ "is-terminal",
+ "itertools 0.10.5",
+ "num-traits",
+ "once_cell",
+ "oorandom",
+ "plotters",
+ "rayon",
+ "regex",
+ "serde",
+ "serde_derive",
+ "serde_json",
+ "tinytemplate",
+ "walkdir",
+]
+
+[[package]]
+name = "criterion-plot"
+version = "0.5.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "6b50826342786a51a89e2da3a28f1c32b06e387201bc2d19791f622c673706b1"
+dependencies = [
+ "cast",
+ "itertools 0.10.5",
+]
+
 [[package]]
 name = "crossbeam-deque"
 version = "0.8.6"
@@ -1479,6 +1554,7 @@ dependencies = [
  "clap",
  "colored",
  "compact_str",
+ "criterion",
  "glt",
  "iced",
  "indicatif",
@@ -1949,12 +2025,32 @@ dependencies = [
  "syn",
 ]
 
+[[package]]
+name = "is-terminal"
+version = "0.4.17"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "3640c1c38b8e4e43584d8df18be5fc6b0aa314ce6ebf51b53313d4306cca8e46"
+dependencies = [
+ "hermit-abi",
+ "libc",
+ "windows-sys 0.61.2",
+]
+
 [[package]]
 name = "is_terminal_polyfill"
 version = "1.70.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "a6cb138bb79a146c1bd460005623e142ef0181e3d0219cb493e02f7d08a35695"
 
+[[package]]
+name = "itertools"
+version = "0.10.5"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "b0fd2260e829bddf4cb6ea802289de2f86d6a7a690192fbe91b3f46e0f2c8473"
+dependencies = [
+ "either",
+]
+
 [[package]]
 name = "itertools"
 version = "0.14.0"
@@ -2870,6 +2966,12 @@ version = "1.70.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "384b8ab6d37215f3c5301a95a4accb5d64aa607f1fcb26a11b5303878451b4fe"
 
+[[package]]
+name = "oorandom"
+version = "11.1.5"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "d6790f58c7ff633d8771f42965289203411a5e5c68388703c06e14f24770b41e"
+
 [[package]]
 name = "orbclient"
 version = "0.3.54"
@@ -3016,6 +3118,34 @@ version = "0.2.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "b4596b6d070b27117e987119b4dac604f3c58cfb0b191112e24771b2faeac1a6"
 
+[[package]]
+name = "plotters"
+version = "0.3.7"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "5aeb6f403d7a4911efb1e33402027fc44f29b5bf6def3effcc22d7bb75f2b747"
+dependencies = [
+ "num-traits",
+ "plotters-backend",
+ "plotters-svg",
+ "wasm-bindgen",
+ "web-sys",
+]
+
+[[package]]
+name = "plotters-backend"
+version = "0.3.7"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "df42e13c12958a16b3f7f4386b9ab1f3e7933914ecea48da7139435263a4172a"
+
+[[package]]
+name = "plotters-svg"
+version = "0.3.7"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "51bae2ac328883f7acdfea3d66a7c35751187f870bc81f94563733a154d7a670"
+dependencies = [
+ "plotters-backend",
+]
+
 [[package]]
 name = "png"
 version = "0.17.16"
@@ -3241,7 +3371,7 @@ dependencies = [
  "built",
  "cfg-if",
  "interpolate_name",
- "itertools",
+ "itertools 0.14.0",
  "libc",
  "libfuzzer-sys",
  "log",
@@ -4051,6 +4181,16 @@ dependencies = [
  "tracing",
 ]
 
+[[package]]
+name = "tinytemplate"
+version = "1.2.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "be4d6b5f19ff7664e8c98d03e2139cb510db9b0a60b55f8e8709b689d939b6bc"
+dependencies = [
+ "serde",
+ "serde_json",
+]
+
 [[package]]
 name = "tinyvec"
 version = "1.11.0"

Cargo.toml

@@ -20,3 +20,10 @@ rayon = { version = "1.10", optional = true }
 [features]
 default = []
 parallel = ["rayon"]
+
+[dev-dependencies]
+criterion = { version = "0.5", features = ["html_reports"] }
+
+[[bench]]
+name = "bench"
+harness = false

benches/bench.rs

@@ -0,0 +1,99 @@
+use criterion::{criterion_group, criterion_main, Criterion};
+
+fn bench_matching_rules(c: &mut Criterion) {
+    let mut group = c.benchmark_group("matching_rules");
+    group.sample_size(10);
+
+    group.bench_function("100_rules", |b| {
+        b.iter(|| {
+            let mut stylesheet = glint_runtime::interpreter::style::StyleSheet::new();
+            for i in 0..100 {
+                stylesheet.add_rule(
+                    format!(".class-{}", i),
+                    std::collections::HashMap::from([("color".into(), "red".into())]),
+                );
+            }
+            stylesheet.build_index();
+            let _ = stylesheet.matching_rules(
+                "Button",
+                None,
+                &["class-1"],
+                &[],
+                &Default::default(),
+                &[],
+                &[],
+                &std::collections::HashMap::new(),
+            );
+        })
+    });
+
+    group.finish();
+}
+
+fn bench_style_compute(c: &mut Criterion) {
+    let mut group = c.benchmark_group("computed_style");
+    group.sample_size(10);
+
+    group.bench_function("compute_empty", |b| {
+        b.iter(|| {
+            let _ = glint_runtime::interpreter::style::ComputedStyle::compute(
+                &[],
+                &[],
+            );
+        })
+    });
+
+    group.bench_function("compute_5_props", |b| {
+        let props: Vec<(std::borrow::Cow<'_, str>, std::borrow::Cow<'_, str>)> = vec![
+            ("color".into(), "red".into()),
+            ("padding".into(), "10px".into()),
+            ("font-size".into(), "16px".into()),
+            ("background".into(), "#fff".into()),
+            ("width".into(), "100px".into()),
+        ];
+        b.iter(|| {
+            let _ = glint_runtime::interpreter::style::ComputedStyle::compute(
+                &props,
+                &[],
+            );
+        })
+    });
+
+    group.finish();
+}
+
+fn bench_resolve_string(c: &mut Criterion) {
+    let mut group = c.benchmark_group("resolve_string");
+    group.sample_size(10);
+
+    let vars = std::collections::HashMap::from([
+        ("name".to_string(), glint_runtime::interpreter::Value::Str("world".into())),
+        ("count".to_string(), glint_runtime::interpreter::Value::Int(42)),
+    ]);
+
+    group.bench_function("no_vars", |b| {
+        b.iter(|| {
+            use glint_runtime::interpreter::Interpreter;
+            let _ = Interpreter::resolve_string("hello world", &vars);
+        })
+    });
+
+    group.bench_function("1_var", |b| {
+        b.iter(|| {
+            use glint_runtime::interpreter::Interpreter;
+            let _ = Interpreter::resolve_string("Hello $name!", &vars);
+        })
+    });
+
+    group.bench_function("3_vars", |b| {
+        b.iter(|| {
+            use glint_runtime::interpreter::Interpreter;
+            let _ = Interpreter::resolve_string("$name has count $count and is $name", &vars);
+        })
+    });
+
+    group.finish();
+}
+
+criterion_group!(benches, bench_matching_rules, bench_style_compute, bench_resolve_string);
+criterion_main!(benches);

src/app.rs

@@ -4,6 +4,7 @@ use iced::widget::{column, container};
 use iced::{Length, Theme};
 
 use crate::interpreter::{Document, Element, Interpreter, RheiContext, Value};
+use crate::perf;
 use crate::renderer::render_element;
 use crate::Message;
 
@@ -63,6 +64,7 @@ impl GlintApp {
 
         let dirty_set = self.doc.tracker.take_dirty_set();
         let root_refs: Vec<&Element<'static>> = self.doc.roots.iter().collect();
+        let _vdom_scope = perf::PerfScope::new("vdom");
         self.vdom_roots = Interpreter::evaluate_vdom_incr(
             &root_refs,
             &mut self.doc.variables,
@@ -72,11 +74,13 @@ impl GlintApp {
             &[],
             &dirty_set,
         );
+        drop(_vdom_scope);
 
         iced::Task::none()
     }
 
     pub fn view(&self) -> iced::Element<'_, Message, Theme, iced::Renderer> {
+        let _render_scope = perf::PerfScope::new("render");
         let mut content = column![]
             .width(Length::Fill)
             .height(Length::Fill);
@@ -115,20 +119,25 @@ impl GlintApp {
         let has_sticky = !global_sticky_layers.is_empty();
         let has_fixed = !global_fixed_layers.is_empty();
 
-        if !has_abs && !has_sticky && !has_fixed {
+        let render_result = {
-            main_flow.into()
+            if !has_abs && !has_sticky && !has_fixed {
-        } else {
+                main_flow.into()
-            let mut stack_widget = iced::widget::stack![main_flow];
+            } else {
-            for layer in global_abs_layers {
+                let mut stack_widget = iced::widget::stack![main_flow];
-                stack_widget = stack_widget.push(layer);
+                for layer in global_abs_layers {
+                    stack_widget = stack_widget.push(layer);
+                }
+                for layer in global_sticky_layers {
+                    stack_widget = stack_widget.push(layer);
+                }
+                for layer in global_fixed_layers {
+                    stack_widget = stack_widget.push(layer);
+                }
+                stack_widget.into()
             }
-            for layer in global_sticky_layers {
+        };
-                stack_widget = stack_widget.push(layer);
+        drop(_render_scope);
-            }
+        perf::print_frame();
-            for layer in global_fixed_layers {
+        render_result
-                stack_widget = stack_widget.push(layer);
-            }
-            stack_widget.into()
-        }
     }
 }

src/interpreter/style.rs

@@ -821,6 +821,7 @@ impl StyleSheet {
         props: &[(Cow<'_, str>, Cow<'_, str>)],
         matched_sheets: &[&'a HashMap<String, String>],
     ) -> ComputedStyle {
+        let _scope = crate::perf::PerfScope::new("style");
         let epoch = self.epoch;
         self.cache.lock().unwrap().get_or_compute(type_name, props, epoch, matched_sheets)
     }

src/lib.rs

@@ -0,0 +1,21 @@
+pub mod app;
+pub mod cli;
+pub mod interpreter;
+pub mod perf;
+pub mod renderer;
+
+pub use app::GlintApp;
+pub use interpreter::{Element, Interpreter, RheiContext, Value};
+pub use interpreter::style::{ComputedStyle, StyleSheet};
+pub use interpreter::types::{Document, Interner};
+pub use interpreter::reactive::{ElementId, ReactiveTracker};
+
+#[derive(Debug, Clone)]
+pub enum Message {
+    EventTriggered(String),
+    InputChanged(Option<String>, String),
+    ToggleChanged(Option<String>, bool),
+    SliderChanged(Option<String>, f64),
+    WindowScrolled(f32),
+    ScrollableScrolled(u64, f32),
+}

src/main.rs

@@ -1,19 +1,11 @@
 mod app;
 mod cli;
 mod interpreter;
+mod perf;
 mod renderer;
 
 use clap::{Parser, Subcommand};
-
+use glint_runtime::Message;
-#[derive(Debug, Clone)]
-pub enum Message {
-    EventTriggered(String),
-    InputChanged(Option<String>, String),
-    ToggleChanged(Option<String>, bool),
-    SliderChanged(Option<String>, f64),
-    WindowScrolled(f32),
-    ScrollableScrolled(u64, f32),
-}
 
 #[derive(Parser)]
 #[command(name = "glint-runtime")]
@@ -39,6 +31,10 @@ enum Commands {
     Run {
         /// Bytecode file to execute
         file: String,
+
+        /// Print per-frame performance metrics (VDOM/Style/Render timing)
+        #[arg(long)]
+        perf: bool,
     },
 }
 
@@ -59,7 +55,10 @@ fn main() {
             });
             cli::compile_files(&gltm_files, &glts_files, &output_path);
         }
-        Commands::Run { file } => {
+        Commands::Run { file, perf } => {
+            if perf {
+                crate::perf::set_enabled(true);
+            }
             cli::run_file(&file);
         }
     }

src/perf.rs

@@ -0,0 +1,87 @@
+use std::cell::{Cell, RefCell};
+use std::time::Instant;
+
+#[derive(Debug, Clone, Default)]
+pub struct PerfReport {
+    pub vdom_eval: f64,
+    pub style: f64,
+    pub render: f64,
+    pub total: f64,
+}
+
+thread_local! {
+    static PERF_ENABLED: Cell<bool> = Cell::new(false);
+    static PERF_REPORT: RefCell<PerfReport> = RefCell::new(PerfReport::default());
+}
+
+pub fn set_enabled(enabled: bool) {
+    PERF_ENABLED.with(|e| e.set(enabled));
+}
+
+pub fn is_enabled() -> bool {
+    PERF_ENABLED.with(|e| e.get())
+}
+
+pub struct PerfScope {
+    name: &'static str,
+    start: Instant,
+}
+
+impl PerfScope {
+    pub fn new(name: &'static str) -> Self {
+        Self {
+            name,
+            start: Instant::now(),
+        }
+    }
+}
+
+impl Drop for PerfScope {
+    fn drop(&mut self) {
+        if !is_enabled() {
+            return;
+        }
+        let ms = self.start.elapsed().as_secs_f64() * 1000.0;
+        PERF_REPORT.with(|r| {
+            let mut r = r.borrow_mut();
+            match self.name {
+                "vdom" => r.vdom_eval += ms,
+                "style" => r.style += ms,
+                "render" => r.render += ms,
+                _ => {}
+            }
+        });
+    }
+}
+
+pub fn report_and_reset() -> Option<String> {
+    if !is_enabled() {
+        return None;
+    }
+    PERF_REPORT.with(|r| {
+        let r = r.borrow();
+        let total = r.vdom_eval + r.style + r.render;
+        let mut out = format!(
+            "VDOM: {:.2}ms | Style: {:.2}ms | Render: {:.2}ms | Total: {:.2}ms",
+            r.vdom_eval, r.style, r.render, total
+        );
+        if total > 16.0 {
+            out.push_str(&format!(
+                " ⚠️ Frame budget exceeded! {:.2}ms > 16ms",
+                total
+            ));
+        }
+        Some(out)
+    })
+}
+
+pub fn reset() {
+    PERF_REPORT.with(|r| *r.borrow_mut() = PerfReport::default());
+}
+
+pub fn print_frame() {
+    if let Some(report) = report_and_reset() {
+        eprintln!("[perf] {}", report);
+    }
+    reset();
+}