On Web, implement navigating back/forward with mouse buttons (#5792)

### What
By popular request

### 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 newly built examples:
[rerun.io/viewer](https://rerun.io/viewer/pr/5792)
* Using examples from latest `main` build:
[rerun.io/viewer](https://rerun.io/viewer/pr/5792?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/5792?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)!

- [PR Build Summary](https://build.rerun.io/pr/5792)
- [Docs
preview](https://rerun.io/preview/fb21b7fbbebe58182dfe33276e81c59540393683/docs)
<!--DOCS-PREVIEW-->
- [Examples
preview](https://rerun.io/preview/fb21b7fbbebe58182dfe33276e81c59540393683/examples)
<!--EXAMPLES-PREVIEW-->
- [Recent benchmark results](https://build.rerun.io/graphs/crates.html)
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crates/re_viewer/src/app.rs

@@ -1320,6 +1320,22 @@ impl eframe::App for App {
                 .add(egui_ctx.input(|i| i.time), seconds);
         }
 
+        #[cfg(target_arch = "wasm32")]
+        {
+            // Handle pressing the back/forward mouse buttons explicitly, since eframe catches those.
+            let back_pressed =
+                egui_ctx.input(|i| i.pointer.button_pressed(egui::PointerButton::Extra1));
+            let fwd_pressed =
+                egui_ctx.input(|i| i.pointer.button_pressed(egui::PointerButton::Extra2));
+
+            if back_pressed {
+                crate::web_tools::go_back();
+            }
+            if fwd_pressed {
+                crate::web_tools::go_forward();
+            }
+        }
+
         // Temporarily take the `StoreHub` out of the Viewer so it doesn't interfere with mutability
         let mut store_hub = self.store_hub.take().unwrap();
 

crates/re_viewer/src/web_tools.rs

@@ -31,6 +31,28 @@ pub fn percent_encode(s: &str) -> String {
     format!("{}", js_sys::encode_uri_component(s))
 }
 
+pub fn go_back() -> Option<()> {
+    let history = web_sys::window()?
+        .history()
+        .map_err(|err| format!("Failed to get History API: {}", string_from_js_value(err)))
+        .ok_or_log_error()?;
+    history
+        .back()
+        .map_err(|err| format!("Failed to go back: {}", string_from_js_value(err)))
+        .ok_or_log_error()
+}
+
+pub fn go_forward() -> Option<()> {
+    let history = web_sys::window()?
+        .history()
+        .map_err(|err| format!("Failed to get History API: {}", string_from_js_value(err)))
+        .ok_or_log_error()?;
+    history
+        .forward()
+        .map_err(|err| format!("Failed to go forward: {}", string_from_js_value(err)))
+        .ok_or_log_error()
+}
+
 /// The current percent-encoded URL suffix, e.g. "?foo=bar#baz".
 pub fn current_url_suffix() -> Option<String> {
     let location = web_sys::window()?.location();