Add test for ui wakeup

Cargo.lock

@@ -7107,6 +7107,16 @@ dependencies = [
  "rerun",
 ]
 
+[[package]]
+name = "test_ui_wakeup"
+version = "0.19.0-alpha.1+dev"
+dependencies = [
+ "anyhow",
+ "clap",
+ "re_log",
+ "rerun",
+]
+
 [[package]]
 name = "thiserror"
 version = "1.0.63"

crates/viewer/re_viewer/src/app.rs

@@ -1034,6 +1034,8 @@ impl App {
         let start = web_time::Instant::now();
 
         while let Some((channel_source, msg)) = self.rx.try_recv() {
+            re_log::trace!("Received a message from {channel_source:?}"); // Used by `test_ui_wakeup` test app!
+
             let msg = match msg.payload {
                 re_smart_channel::SmartMessagePayload::Msg(msg) => msg,
 

tests/rust/test_ui_wakeup/Cargo.toml

@@ -0,0 +1,20 @@
+[package]
+name = "test_ui_wakeup"
+version.workspace = true
+edition.workspace = true
+rust-version.workspace = true
+license.workspace = true
+publish = false
+
+[lints]
+workspace = true
+
+[dependencies]
+re_log = { workspace = true, features = ["setup"] }
+rerun = { path = "../../../crates/top/rerun", features = [
+  "clap",
+  "web_viewer",
+] }
+
+anyhow.workspace = true
+clap = { workspace = true, features = ["derive"] }

tests/rust/test_ui_wakeup/src/main.rs

@@ -0,0 +1,63 @@
+//! Test that the Rerun Viewer UI wakes up as new messages arrive,
+//! even if the viewer is hidden.
+//!
+//! ## Test setup - build the viewer
+//! * `pixi run rerun-build`
+//! * `pixi run rerun-build-web`
+//!
+//! ## Test matrix
+//! * Run `cargo r -p test_ui_wakeup` and test:
+//!   * That the viewer wakes up in the background when it's alt-tabbed
+//!   * That the viewer wakes up when minimized (it should log "Received a message from…")
+//! * Run `cargo r -p test_ui_wakeup -- --serve` and test:
+//!   * The viewer wakes up when browser is alt-tabbed away
+//!   * Switch to a different browser tab, send a few messages, switch back. The messages should be there
+//!     (this is not a conclusive test, as the messages might have been received on tab select)
+
+use std::io::Read as _;
+
+#[derive(Debug, clap::Parser)]
+#[clap(author, version, about)]
+struct Args {
+    #[command(flatten)]
+    rerun: rerun::clap::RerunArgs,
+}
+
+fn main() -> anyhow::Result<()> {
+    re_log::setup_logging();
+
+    use clap::Parser as _;
+    let args = Args::parse();
+
+    // This is so that re_viewer logs incoming messages:
+    let rust_log = "info,re_viewer=trace";
+    eprintln!("Setting RUST_LOG={rust_log}");
+    std::env::set_var("RUST_LOG", rust_log);
+
+    println!("Starting Viewer…");
+    let (rec, _serve_guard) = args.rerun.init("rerun_example_ui_wakeup")?;
+
+    // Wait out some log spam from the viewer starting:
+    std::thread::sleep(std::time::Duration::from_secs(1));
+
+    println!("Now put the viewer in the background (alt-tab, minimize, put in background tab, etc");
+
+    for i in 0..usize::MAX {
+        println!("Sending message number {i}…");
+        rec.log(
+            "Text",
+            &rerun::TextDocument::new(format!("This is message number {i}")),
+        )?;
+        println!("Press ENTER to send more data to the viewer");
+
+        wait_from_enter();
+    }
+
+    Ok(())
+}
+
+fn wait_from_enter() {
+    let _ = std::io::stdin()
+        .read(&mut [0u8])
+        .expect("Failed to read from stdin");
+}