Replace tracing with log (#2928)

* Replace tracing crate with log

It's just so much simpler to use

* Add `bacon wasm` job

* eframe: add a WebLogger for piping log events to the web console

crates/egui/Cargo.toml

@@ -45,6 +45,9 @@ extra_debug_asserts = ["epaint/extra_debug_asserts"]
 ## Always enable additional checks.
 extra_asserts = ["epaint/extra_asserts"]
 
+## Turn on the `log` feature, that makes egui log some errors using the [`log`](https://docs.rs/log) crate.
+log = ["dep:log", "epaint/log"]
+
 ## [`mint`](https://docs.rs/mint) enables interoperability with other math libraries such as [`glam`](https://docs.rs/glam) and [`nalgebra`](https://docs.rs/nalgebra).
 mint = ["epaint/mint"]
 
@@ -75,10 +78,6 @@ accesskit = { version = "0.10.1", optional = true }
 ## Enable this when generating docs.
 document-features = { version = "0.2", optional = true }
 
+log = { version = "0.4", optional = true, features = ["std"] }
 ron = { version = "0.8", optional = true }
 serde = { version = "1", optional = true, features = ["derive", "rc"] }
-
-# egui doesn't log much, but when it does, it uses [`tracing`](https://docs.rs/tracing).
-tracing = { version = "0.1", optional = true, default-features = false, features = [
-    "std",
-] }

crates/egui/src/os.rs

@@ -65,8 +65,8 @@ impl OperatingSystem {
         {
             Self::Nix
         } else {
-            #[cfg(feature = "tracing")]
-            tracing::warn!(
+            #[cfg(feature = "log")]
+            log::warn!(
                 "egui: Failed to guess operating system from User-Agent {:?}. Please file an issue at https://github.com/emilk/egui/issues",
                 user_agent);
 

crates/egui/src/util/id_type_map.rs

@@ -286,8 +286,8 @@ fn from_ron_str<T: serde::de::DeserializeOwned>(ron: &str) -> Option<T> {
     match ron::from_str::<T>(ron) {
         Ok(value) => Some(value),
         Err(_err) => {
-            #[cfg(feature = "tracing")]
-            tracing::warn!(
+            #[cfg(feature = "log")]
+            log::warn!(
                 "egui: Failed to deserialize {} from memory: {}, ron error: {:?}",
                 std::any::type_name::<T>(),
                 _err,