Add logging/tracing support

demo/Cargo.toml

@@ -18,3 +18,11 @@ parley = { git = "https://github.com/linebender/parley", features = ["accesskit"
 peniko = { version = "0.3.1", default-features = false }
 pollster = "0.4.0"
 vello = "0.4.0"
+
+# Send tracing events to Android GPU inspector, for profiling
+tracing_android_trace = "0.1.1"
+tracing-subscriber = "0.3.19"
+# Make events recorded with profiling (e.g. in wgpu) visible to Android GPU inspector
+profiling = { version = "1.0.16", features = ["profile-with-tracing"] }
+# Make events recorded to `tracing` visible in logcat
+tracing = { version = "0.1.38", features = ["log-always"] }

demo/src/lib.rs

@@ -20,6 +20,7 @@ use log::LevelFilter;
 use std::ffi::c_void;
 use std::num::NonZeroUsize;
 use std::time::Instant;
+use tracing_subscriber::{layer::SubscriberExt, util::SubscriberInitExt};
 use vello::kurbo;
 use vello::peniko::Color;
 use vello::util::{RenderContext, RenderSurface};
@@ -525,6 +526,13 @@ pub unsafe extern "system" fn JNI_OnLoad(vm: *mut RawJavaVM, _: *mut c_void) ->
             .with_max_level(LevelFilter::Trace)
             .with_tag("android-view-demo"),
     );
+    // This will try to create a "log" logger, and error because one was already created above
+    // We therefore ignore the error
+    // Ideally, we'd only ignore the SetLoggerError, but the only way that's possible is to inspect
+    // `Debug/Display` on the TryInitError, which is awful.
+    let _ = tracing_subscriber::registry()
+        .with(tracing_android_trace::AndroidTraceLayer::new())
+        .try_init();
 
     let vm = unsafe { JavaVM::from_raw(vm) }.unwrap();
     let mut env = vm.get_env().unwrap();