Add web location info to egui_web/epi (#1258)

This adds all parts of the web "location" (URL) to frame.info().web_info, included a HashMap of the query parameters, percent-decoded and ready to go.

This lets you easily pass key-value pairs to your eframe web app.

egui_web/src/backend.rs

@@ -81,6 +81,77 @@ impl epi::backend::RepaintSignal for NeedRepaint {
 
 // ----------------------------------------------------------------------------
 
+fn web_location() -> epi::Location {
+    let location = web_sys::window().unwrap().location();
+
+    let hash = percent_decode(&location.hash().unwrap_or_default());
+
+    let query = location
+        .search()
+        .unwrap_or_default()
+        .strip_prefix('?')
+        .map(percent_decode)
+        .unwrap_or_default();
+
+    let query_map = parse_query_map(&query)
+        .iter()
+        .map(|(k, v)| (k.to_string(), v.to_string()))
+        .collect();
+
+    epi::Location {
+        url: percent_decode(&location.href().unwrap_or_default()),
+        protocol: percent_decode(&location.protocol().unwrap_or_default()),
+        host: percent_decode(&location.host().unwrap_or_default()),
+        hostname: percent_decode(&location.hostname().unwrap_or_default()),
+        port: percent_decode(&location.port().unwrap_or_default()),
+        hash,
+        query,
+        query_map,
+        origin: percent_decode(&location.origin().unwrap_or_default()),
+    }
+}
+
+fn parse_query_map(query: &str) -> BTreeMap<&str, &str> {
+    query
+        .split('&')
+        .filter_map(|pair| {
+            if pair.is_empty() {
+                None
+            } else {
+                Some(if let Some((key, value)) = pair.split_once('=') {
+                    (key, value)
+                } else {
+                    (pair, "")
+                })
+            }
+        })
+        .collect()
+}
+
+#[test]
+fn test_parse_query() {
+    assert_eq!(parse_query_map(""), BTreeMap::default());
+    assert_eq!(parse_query_map("foo"), BTreeMap::from_iter([("foo", "")]));
+    assert_eq!(
+        parse_query_map("foo=bar"),
+        BTreeMap::from_iter([("foo", "bar")])
+    );
+    assert_eq!(
+        parse_query_map("foo=bar&baz=42"),
+        BTreeMap::from_iter([("foo", "bar"), ("baz", "42")])
+    );
+    assert_eq!(
+        parse_query_map("foo&baz=42"),
+        BTreeMap::from_iter([("foo", ""), ("baz", "42")])
+    );
+    assert_eq!(
+        parse_query_map("foo&baz&&"),
+        BTreeMap::from_iter([("foo", ""), ("baz", "")])
+    );
+}
+
+// ----------------------------------------------------------------------------
+
 pub struct AppRunner {
     pub(crate) frame: epi::Frame,
     egui_ctx: egui::Context,
@@ -108,7 +179,7 @@ impl AppRunner {
             info: epi::IntegrationInfo {
                 name: painter.name(),
                 web_info: Some(epi::WebInfo {
-                    web_location_hash: location_hash().unwrap_or_default(),
+                    location: web_location(),
                 }),
                 prefer_dark_mode,
                 cpu_usage: None,

egui_web/src/lib.rs

@@ -33,6 +33,7 @@ pub use web_sys;
 
 pub use painter::Painter;
 use std::cell::Cell;
+use std::collections::BTreeMap;
 use std::rc::Rc;
 use std::sync::Arc;
 use wasm_bindgen::prelude::*;
@@ -353,9 +354,23 @@ pub fn open_url(url: &str, new_tab: bool) -> Option<()> {
     Some(())
 }
 
-/// e.g. "#fragment" part of "www.example.com/index.html#fragment"
-pub fn location_hash() -> Option<String> {
-    web_sys::window()?.location().hash().ok()
+/// e.g. "#fragment" part of "www.example.com/index.html#fragment",
+///
+/// Percent decoded
+pub fn location_hash() -> String {
+    percent_decode(
+        &web_sys::window()
+            .unwrap()
+            .location()
+            .hash()
+            .unwrap_or_default(),
+    )
+}
+
+pub fn percent_decode(s: &str) -> String {
+    percent_encoding::percent_decode_str(s)
+        .decode_utf8_lossy()
+        .to_string()
 }
 
 /// Web sends all keys as strings, so it is up to us to figure out if it is
@@ -661,7 +676,7 @@ fn install_document_events(runner_ref: &AppRunnerRef) -> Result<(), JsValue> {
 
             // `epi::Frame::info(&self)` clones `epi::IntegrationInfo`, but we need to modify the original here
             if let Some(web_info) = &mut frame_lock.info.web_info {
-                web_info.web_location_hash = location_hash().unwrap_or_default();
+                web_info.location.hash = location_hash();
             }
         }) as Box<dyn FnMut()>);
         window.add_event_listener_with_callback("hashchange", closure.as_ref().unchecked_ref())?;