Use tracing in examples

madsmtm · madsmtm · commit 89008ef2e055 · 2026-01-17T08:22:01.000+01:00
println! and eprintln! are no-ops on WASM.
diff --git a/Cargo.toml b/Cargo.toml
@@ -134,6 +134,7 @@ redox_syscall = "0.7"
 colorous = "1.0.12"
 web-time = "1.0.0"
 winit = "0.30.0"
+tracing-subscriber = { version = "0.3.18", features = ["env-filter"] }
 
 [target.'cfg(target_os = "android")'.dev-dependencies]
 winit = { version = "0.30.0", features = ["android-native-activity"] }
@@ -155,6 +156,7 @@ criterion = { version = "0.8.1", default-features = false, features = [
 [target.'cfg(target_family = "wasm")'.dev-dependencies]
 wasm-bindgen-test = "0.3"
 console_error_panic_hook = "0.1"
+tracing-web = "0.1"
 
 [target.'cfg(not(any(target_os = "android", target_vendor = "apple", target_os = "redox", target_family = "wasm", target_os = "windows")))'.dev-dependencies]
 rustix = { version = "1.0.1", features = ["event"] }
diff --git a/README.md b/README.md
@@ -98,7 +98,7 @@ fn main() {
         match event {
             WindowEvent::RedrawRequested => {
                 let Some(surface) = surface else {
-                    eprintln!("RedrawRequested fired before Resumed or after Suspended");
+                    tracing::error!("RedrawRequested fired before Resumed or after Suspended");
                     return;
                 };
                 let size = window.inner_size();
diff --git a/clippy.toml b/clippy.toml
@@ -0,0 +1,6 @@
+disallowed-macros = [
+    { path = "std::print", reason = "use tracing in examples instead, that works on WASM too" },
+    { path = "std::eprint", reason = "use tracing in examples instead, that works on WASM too" },
+    { path = "std::println", reason = "use tracing in examples instead, that works on WASM too" },
+    { path = "std::eprintln", reason = "use tracing in examples instead, that works on WASM too" },
+]
diff --git a/examples/animation.rs b/examples/animation.rs
@@ -42,7 +42,7 @@ fn main() {
         match event {
             WindowEvent::Resized(size) => {
                 let Some(surface) = surface else {
-                    eprintln!("Resized fired before Resumed or after Suspended");
+                    tracing::error!("Resized fired before Resumed or after Suspended");
                     return;
                 };
 
@@ -54,7 +54,7 @@ fn main() {
             }
             WindowEvent::RedrawRequested => {
                 let Some(surface) = surface else {
-                    eprintln!("RedrawRequested fired before Resumed or after Suspended");
+                    tracing::error!("RedrawRequested fired before Resumed or after Suspended");
                     return;
                 };
 
diff --git a/examples/drm.rs b/examples/drm.rs
@@ -124,7 +124,7 @@ mod imple {
         let mut tick = 0;
         while Instant::now().duration_since(start) < Duration::from_secs(2) {
             tick += 1;
-            println!("Drawing tick {tick}");
+            tracing::info!("Drawing tick {tick}");
 
             // Start drawing.
             let mut buffer = surface.buffer_mut()?;
@@ -142,17 +142,17 @@ mod imple {
 
             // Receive the events.
             let events = device.receive_events()?;
-            println!("Got some events...");
+            tracing::info!("Got some events...");
             for event in events {
                 match event {
                     Event::PageFlip(_) => {
-                        println!("Page flip event.");
+                        tracing::info!("Page flip event.");
                     }
                     Event::Vblank(_) => {
-                        println!("Vblank event.");
+                        tracing::info!("Vblank event.");
                     }
                     _ => {
-                        println!("Unknown event.");
+                        tracing::info!("Unknown event.");
                     }
                 }
             }
@@ -233,8 +233,7 @@ mod imple {
 )))]
 mod imple {
     pub(super) fn entry() -> Result<(), Box<dyn std::error::Error>> {
-        eprintln!("This example requires the `kms` feature.");
-        Ok(())
+        panic!("This example requires the `kms` feature.")
     }
 }
 
diff --git a/examples/fruit.rs b/examples/fruit.rs
@@ -46,7 +46,7 @@ fn main() {
         match event {
             WindowEvent::RedrawRequested => {
                 let Some(surface) = surface else {
-                    eprintln!("RedrawRequested fired before Resumed or after Suspended");
+                    tracing::error!("RedrawRequested fired before Resumed or after Suspended");
                     return;
                 };
 
diff --git a/examples/libxcb.rs b/examples/libxcb.rs
@@ -175,5 +175,5 @@ fn main() {
 fn main() {
     util::setup();
 
-    eprintln!("This example requires the `x11` feature to be enabled on a supported platform.");
+    panic!("This example requires the `x11` feature to be enabled on a supported platform.")
 }
diff --git a/examples/rectangle.rs b/examples/rectangle.rs
@@ -55,7 +55,7 @@ fn main() {
         match event {
             WindowEvent::Resized(size) => {
                 let Some(surface) = surface else {
-                    eprintln!("Resized fired before Resumed or after Suspended");
+                    tracing::error!("Resized fired before Resumed or after Suspended");
                     return;
                 };
 
@@ -68,7 +68,7 @@ fn main() {
             }
             WindowEvent::RedrawRequested => {
                 let Some(surface) = surface else {
-                    eprintln!("RedrawRequested fired before Resumed or after Suspended");
+                    tracing::error!("RedrawRequested fired before Resumed or after Suspended");
                     return;
                 };
                 // Draw something in the window
diff --git a/examples/util/mod.rs b/examples/util/mod.rs
@@ -4,8 +4,35 @@ mod winit_app;
 #[allow(unused_imports)]
 pub use self::winit_app::*;
 
-/// Set up the console error hook on WebAssembly.
+/// Initialize an appropriate tracing subscriber, and set the console error hook on WASM.
 pub fn setup() {
+    #[cfg(not(target_family = "wasm"))]
+    {
+        use tracing_subscriber::filter::{EnvFilter, LevelFilter};
+
+        tracing_subscriber::fmt()
+            .with_env_filter(
+                EnvFilter::builder()
+                    .with_default_directive(LevelFilter::INFO.into())
+                    .from_env_lossy(),
+            )
+            .init();
+    }
+
     #[cfg(target_family = "wasm")]
-    console_error_panic_hook::set_once();
+    {
+        console_error_panic_hook::set_once();
+
+        use tracing_subscriber::layer::SubscriberExt;
+        use tracing_subscriber::util::SubscriberInitExt;
+
+        tracing_subscriber::registry()
+            .with(
+                tracing_subscriber::fmt::layer()
+                    .with_ansi(false)
+                    .without_time()
+                    .with_writer(tracing_web::MakeWebConsoleWriter::new()),
+            )
+            .init();
+    }
 }
diff --git a/examples/winit.rs b/examples/winit.rs
@@ -29,7 +29,7 @@ pub(crate) fn entry(event_loop: EventLoop<()>) {
         match event {
             WindowEvent::Resized(size) => {
                 let Some(surface) = surface else {
-                    eprintln!("Resized fired before Resumed or after Suspended");
+                    tracing::error!("Resized fired before Resumed or after Suspended");
                     return;
                 };
 
@@ -41,7 +41,7 @@ pub(crate) fn entry(event_loop: EventLoop<()>) {
             }
             WindowEvent::RedrawRequested => {
                 let Some(surface) = surface else {
-                    eprintln!("RedrawRequested fired before Resumed or after Suspended");
+                    tracing::error!("RedrawRequested fired before Resumed or after Suspended");
                     return;
                 };
 
diff --git a/examples/winit_multithread.rs b/examples/winit_multithread.rs
@@ -20,15 +20,15 @@ pub mod ex {
         done: mpsc::Sender<()>,
     ) {
         loop {
-            println!("waiting for render...");
+            tracing::info!("waiting for render...");
             let Ok((surface, width, height)) = do_render.recv() else {
-                println!("main thread destroyed");
+                tracing::info!("main thread destroyed");
                 break;
             };
 
             // Perform the rendering.
             let mut surface = surface.lock().unwrap();
-            println!("resizing...");
+            tracing::info!("resizing...");
             surface.resize(width, height).unwrap();
 
             let mut buffer = surface.buffer_mut().unwrap();
@@ -42,7 +42,7 @@ pub mod ex {
                 }
             }
 
-            println!("presenting...");
+            tracing::info!("presenting...");
             buffer.present().unwrap();
 
             // We're done, tell the main thread to keep going.
@@ -67,13 +67,13 @@ pub mod ex {
                 // when a new surface is created.
                 let (start_render, do_render) = mpsc::channel();
                 let (render_done, finish_render) = mpsc::channel();
-                println!("starting thread...");
+                tracing::info!("starting thread...");
                 std::thread::spawn(move || render_thread(do_render, render_done));
 
                 (window, start_render, finish_render)
             },
             move |_elwt, (window, _start_render, _finish_render)| {
-                println!("making surface...");
+                tracing::info!("making surface...");
                 Arc::new(Mutex::new(
                     softbuffer::Surface::new(&context, window.clone()).unwrap(),
                 ))
@@ -90,12 +90,12 @@ pub mod ex {
             match event {
                 WindowEvent::RedrawRequested => {
                     let Some(surface) = surface else {
-                        eprintln!("RedrawRequested fired before Resumed or after Suspended");
+                        tracing::error!("RedrawRequested fired before Resumed or after Suspended");
                         return;
                     };
 
                     let size = window.inner_size();
-                    println!("got size: {size:?}");
+                    tracing::info!("got size: {size:?}");
                     if let (Some(width), Some(height)) =
                         (NonZeroU32::new(size.width), NonZeroU32::new(size.height))
                     {
@@ -127,7 +127,7 @@ pub mod ex {
 mod ex {
     use winit::event_loop::EventLoop;
     pub(crate) fn entry(_event_loop: EventLoop<()>) {
-        eprintln!("winit_multithreaded doesn't work on WASM");
+        panic!("winit_multithreaded doesn't work on WASM")
     }
 }
 
diff --git a/examples/winit_wrong_sized_buffer.rs b/examples/winit_wrong_sized_buffer.rs
@@ -32,7 +32,7 @@ fn main() {
         match event {
             WindowEvent::RedrawRequested => {
                 let Some(surface) = surface else {
-                    eprintln!("RedrawRequested fired before Resumed or after Suspended");
+                    tracing::warn!("RedrawRequested fired before Resumed or after Suspended");
                     return;
                 };
 

Original file line number	Diff line number	Diff line change
`@@ -124,7 +124,7 @@ mod imple {`
`124`	`124`	`let mut tick = 0;`
`125`	`125`	`while Instant::now().duration_since(start) < Duration::from_secs(2) {`
`126`	`126`	`tick += 1;`
`127`		`- println!("Drawing tick {tick}");`
	`127`	`+ tracing::info!("Drawing tick {tick}");`
`128`	`128`
`129`	`129`	`// Start drawing.`
`130`	`130`	`let mut buffer = surface.buffer_mut()?;`
`@@ -142,17 +142,17 @@ mod imple {`
`142`	`142`
`143`	`143`	`// Receive the events.`
`144`	`144`	`let events = device.receive_events()?;`
`145`		`- println!("Got some events...");`
	`145`	`+ tracing::info!("Got some events...");`
`146`	`146`	`for event in events {`
`147`	`147`	`match event {`
`148`	`148`	`Event::PageFlip(_) => {`
`149`		`- println!("Page flip event.");`
	`149`	`+ tracing::info!("Page flip event.");`
`150`	`150`	`}`
`151`	`151`	`Event::Vblank(_) => {`
`152`		`- println!("Vblank event.");`
	`152`	`+ tracing::info!("Vblank event.");`
`153`	`153`	`}`
`154`	`154`	`_ => {`
`155`		`- println!("Unknown event.");`
	`155`	`+ tracing::info!("Unknown event.");`
`156`	`156`	`}`
`157`	`157`	`}`
`158`	`158`	`}`
`@@ -233,8 +233,7 @@ mod imple {`
`233`	`233`	`)))]`
`234`	`234`	`mod imple {`
`235`	`235`	`pub(super) fn entry() -> Result<(), Box<dyn std::error::Error>> {`
`236`		- eprintln!("This example requires the `kms` feature.");
`237`		`- Ok(())`
	`236`	+ panic!("This example requires the `kms` feature.")
`238`	`237`	`}`
`239`	`238`	`}`
`240`	`239`
Original file line number	Diff line number	Diff line change
`@@ -175,5 +175,5 @@ fn main() {`
`175`	`175`	`fn main() {`
`176`	`176`	`util::setup();`
`177`	`177`
`178`		- eprintln!("This example requires the `x11` feature to be enabled on a supported platform.");
	`178`	+ panic!("This example requires the `x11` feature to be enabled on a supported platform.")
`179`	`179`	`}`