Add test for UI wakeup (rerun-io#7422)

### What
* Part of rerun-io#7378

### Issues found
* rerun-io#7425
* emilk/egui#5114
* rerun-io#7427

## How to test
#### 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)

## Tested

### Web
* [x] ✅ Browser alt-tabbed
* [x] ❌ Web background tab
* Has never _properly_ worked. Is blocked on
emilk/egui#5112
  * It catches up when we switch back to the tab though
       
### Linux
* [x] ✅X11 alt-tabbed
* [x] ✅ X11 minimized
* [x] ✅  Wayland alt-tabbed
* [x] ❌ Wayland minimized (Hyprland placed on non-visible workspace)
* [x] ✅ X-Wayland alt-tabbed
* [x] ✅ X-Wayland minimized (Hyprland placed on non-visible workspace)

### Mac
* [x] ✅ Native alt-tabbed
* [x] ✅ Native minimized

### Windows
* [x] ✅ Native alt-tabbed
* [x] ✅ Native minimized

### Checklist
* [x] I have read and agree to [Contributor
Guide](https://github.com/rerun-io/rerun/blob/main/CONTRIBUTING.md) and
the [Code of
Conduct](https://github.com/rerun-io/rerun/blob/main/CODE_OF_CONDUCT.md)
* [x] I've included a screenshot or gif (if applicable)
* [x] I have tested the web demo (if applicable):
* Using examples from latest `main` build:
[rerun.io/viewer](https://rerun.io/viewer/pr/7422?manifest_url=https://app.rerun.io/version/main/examples_manifest.json)
* Using full set of examples from `nightly` build:
[rerun.io/viewer](https://rerun.io/viewer/pr/7422?manifest_url=https://app.rerun.io/version/nightly/examples_manifest.json)
* [x] The PR title and labels are set such as to maximize their
usefulness for the next release's CHANGELOG
* [x] If applicable, add a new check to the [release
checklist](https://github.com/rerun-io/rerun/blob/main/tests/python/release_checklist)!
* [x] If have noted any breaking changes to the log API in
`CHANGELOG.md` and the migration guide

- [PR Build Summary](https://build.rerun.io/pr/7422)
- [Recent benchmark results](https://build.rerun.io/graphs/crates.html)
- [Wasm size tracking](https://build.rerun.io/graphs/sizes.html)

To run all checks from `main`, comment on the PR with `@rerun-bot
full-check`.

---------

Co-authored-by: Antoine Beyeler <[email protected]>

Author: emilk

Cargo.lock

@@ -7111,6 +7111,16 @@ 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.. {
+        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");
+}