2 files changed, 273 insertions, 0 deletions
diff --git a/runtime/src/debug/basic.rs b/runtime/src/debug/basic.rs
new file mode 100644
index 00000000..32f725a1
--- /dev/null
+++ b/runtime/src/debug/basic.rs
@@ -0,0 +1,226 @@
+#![allow(missing_docs)]
+use crate::core::time;
+
+use std::collections::VecDeque;
+
+/// A bunch of time measurements for debugging purposes.
+#[derive(Debug)]
+pub struct Debug {
+    is_enabled: bool,
+
+    startup_start: time::Instant,
+    startup_duration: time::Duration,
+
+    update_start: time::Instant,
+    update_durations: TimeBuffer,
+
+    view_start: time::Instant,
+    view_durations: TimeBuffer,
+
+    layout_start: time::Instant,
+    layout_durations: TimeBuffer,
+
+    event_start: time::Instant,
+    event_durations: TimeBuffer,
+
+    draw_start: time::Instant,
+    draw_durations: TimeBuffer,
+
+    render_start: time::Instant,
+    render_durations: TimeBuffer,
+
+    message_count: usize,
+    last_messages: VecDeque<String>,
+}
+
+impl Debug {
+    /// Creates a new [`struct@Debug`].
+    pub fn new() -> Self {
+        let now = time::Instant::now();
+
+        Self {
+            is_enabled: false,
+            startup_start: now,
+            startup_duration: time::Duration::from_secs(0),
+
+            update_start: now,
+            update_durations: TimeBuffer::new(200),
+
+            view_start: now,
+            view_durations: TimeBuffer::new(200),
+
+            layout_start: now,
+            layout_durations: TimeBuffer::new(200),
+
+            event_start: now,
+            event_durations: TimeBuffer::new(200),
+
+            draw_start: now,
+            draw_durations: TimeBuffer::new(200),
+
+            render_start: now,
+            render_durations: TimeBuffer::new(50),
+
+            message_count: 0,
+            last_messages: VecDeque::new(),
+        }
+    }
+
+    pub fn toggle(&mut self) {
+        self.is_enabled = !self.is_enabled;
+    }
+
+    pub fn startup_started(&mut self) {
+        self.startup_start = time::Instant::now();
+    }
+
+    pub fn startup_finished(&mut self) {
+        self.startup_duration = time::Instant::now() - self.startup_start;
+    }
+
+    pub fn update_started(&mut self) {
+        self.update_start = time::Instant::now();
+    }
+
+    pub fn update_finished(&mut self) {
+        self.update_durations
+            .push(time::Instant::now() - self.update_start);
+    }
+
+    pub fn view_started(&mut self) {
+        self.view_start = time::Instant::now();
+    }
+
+    pub fn view_finished(&mut self) {
+        self.view_durations
+            .push(time::Instant::now() - self.view_start);
+    }
+
+    pub fn layout_started(&mut self) {
+        self.layout_start = time::Instant::now();
+    }
+
+    pub fn layout_finished(&mut self) {
+        self.layout_durations
+            .push(time::Instant::now() - self.layout_start);
+    }
+
+    pub fn event_processing_started(&mut self) {
+        self.event_start = time::Instant::now();
+    }
+
+    pub fn event_processing_finished(&mut self) {
+        self.event_durations
+            .push(time::Instant::now() - self.event_start);
+    }
+
+    pub fn draw_started(&mut self) {
+        self.draw_start = time::Instant::now();
+    }
+
+    pub fn draw_finished(&mut self) {
+        self.draw_durations
+            .push(time::Instant::now() - self.draw_start);
+    }
+
+    pub fn render_started(&mut self) {
+        self.render_start = time::Instant::now();
+    }
+
+    pub fn render_finished(&mut self) {
+        self.render_durations
+            .push(time::Instant::now() - self.render_start);
+    }
+
+    pub fn log_message<Message: std::fmt::Debug>(&mut self, message: &Message) {
+        self.last_messages.push_back(format!("{message:?}"));
+
+        if self.last_messages.len() > 10 {
+            let _ = self.last_messages.pop_front();
+        }
+
+        self.message_count += 1;
+    }
+
+    pub fn overlay(&self) -> Vec<String> {
+        if !self.is_enabled {
+            return Vec::new();
+        }
+
+        let mut lines = Vec::new();
+
+        fn key_value<T: std::fmt::Debug>(key: &str, value: T) -> String {
+            format!("{key} {value:?}")
+        }
+
+        lines.push(format!(
+            "{} {} - {}",
+            env!("CARGO_PKG_NAME"),
+            env!("CARGO_PKG_VERSION"),
+            env!("CARGO_PKG_REPOSITORY"),
+        ));
+        lines.push(key_value("Startup:", self.startup_duration));
+        lines.push(key_value("Update:", self.update_durations.average()));
+        lines.push(key_value("View:", self.view_durations.average()));
+        lines.push(key_value("Layout:", self.layout_durations.average()));
+        lines.push(key_value(
+            "Event processing:",
+            self.event_durations.average(),
+        ));
+        lines.push(key_value(
+            "Primitive generation:",
+            self.draw_durations.average(),
+        ));
+        lines.push(key_value("Render:", self.render_durations.average()));
+        lines.push(key_value("Message count:", self.message_count));
+        lines.push(String::from("Last messages:"));
+        lines.extend(self.last_messages.iter().map(|msg| {
+            if msg.len() <= 100 {
+                format!("    {msg}")
+            } else {
+                format!("    {msg:.100}...")
+            }
+        }));
+
+        lines
+    }
+}
+
+impl Default for Debug {
+    fn default() -> Self {
+        Self::new()
+    }
+}
+
+#[derive(Debug)]
+struct TimeBuffer {
+    head: usize,
+    size: usize,
+    contents: Vec<time::Duration>,
+}
+
+impl TimeBuffer {
+    fn new(capacity: usize) -> TimeBuffer {
+        TimeBuffer {
+            head: 0,
+            size: 0,
+            contents: vec![time::Duration::from_secs(0); capacity],
+        }
+    }
+
+    fn push(&mut self, duration: time::Duration) {
+        self.head = (self.head + 1) % self.contents.len();
+        self.contents[self.head] = duration;
+        self.size = (self.size + 1).min(self.contents.len());
+    }
+
+    fn average(&self) -> time::Duration {
+        let sum: time::Duration = if self.size == self.contents.len() {
+            self.contents[..].iter().sum()
+        } else {
+            self.contents[..self.size].iter().sum()
+        };
+
+        sum / self.size.max(1) as u32
+    }
+}
diff --git a/runtime/src/debug/null.rs b/runtime/src/debug/null.rs
new file mode 100644
index 00000000..2db0eebb
--- /dev/null
+++ b/runtime/src/debug/null.rs
@@ -0,0 +1,47 @@
+#![allow(missing_docs)]
+#[derive(Debug, Default)]
+pub struct Debug;
+
+impl Debug {
+    pub fn new() -> Self {
+        Self
+    }
+
+    pub fn startup_started(&mut self) {}
+
+    pub fn startup_finished(&mut self) {}
+
+    pub fn update_started(&mut self) {}
+
+    pub fn update_finished(&mut self) {}
+
+    pub fn view_started(&mut self) {}
+
+    pub fn view_finished(&mut self) {}
+
+    pub fn layout_started(&mut self) {}
+
+    pub fn layout_finished(&mut self) {}
+
+    pub fn event_processing_started(&mut self) {}
+
+    pub fn event_processing_finished(&mut self) {}
+
+    pub fn draw_started(&mut self) {}
+
+    pub fn draw_finished(&mut self) {}
+
+    pub fn render_started(&mut self) {}
+
+    pub fn render_finished(&mut self) {}
+
+    pub fn log_message<Message: std::fmt::Debug>(
+        &mut self,
+        _message: &Message,
+    ) {
+    }
+
+    pub fn overlay(&self) -> Vec<String> {
+        Vec::new()
+    }
+}