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.

Cargo.lock

@@ -1101,6 +1101,7 @@ dependencies = [
  "egui_glow",
  "epi",
  "js-sys",
+ "percent-encoding",
  "ron",
  "serde",
  "tracing",

eframe/CHANGELOG.md

@@ -14,6 +14,7 @@ NOTE: [`egui_web`](../egui_web/CHANGELOG.md), [`egui-winit`](../egui-winit/CHANG
 * Added `NativeOptions::initial_window_pos`.
 * Shift-scroll will now result in horizontal scrolling on all platforms ([#1136](https://github.com/emilk/egui/pull/1136)).
 * Log using the `tracing` crate. Log to stdout by adding `tracing_subscriber::fmt::init();` to your `main` ([#1192](https://github.com/emilk/egui/pull/1192)).
+* Expose all parts of the location/url in `frame.info().web_info` ([#1258](https://github.com/emilk/egui/pull/1258)).
 
 
 ## 0.16.0 - 2021-12-29

egui_demo_lib/src/backend_panel.rs

@@ -172,6 +172,12 @@ impl BackendPanel {
 
         show_integration_name(ui, &frame.info());
 
+        if let Some(web_info) = &frame.info().web_info {
+            ui.collapsing("Web info (location)", |ui| {
+                ui.monospace(format!("{:#?}", web_info.location));
+            });
+        }
+
         // For instance: `egui_web` sets `pixels_per_point` every frame to force
         // egui to use the same scale as the web zoom factor.
         let integration_controls_pixels_per_point = ui.input().raw.pixels_per_point.is_some();

egui_demo_lib/src/wrap_app.rs

@@ -69,7 +69,7 @@ impl epi::App for WrapApp {
 
     fn update(&mut self, ctx: &egui::Context, frame: &epi::Frame) {
         if let Some(web_info) = frame.info().web_info.as_ref() {
-            if let Some(anchor) = web_info.web_location_hash.strip_prefix('#') {
+            if let Some(anchor) = web_info.location.hash.strip_prefix('#') {
                 self.selected_anchor = anchor.to_owned();
             }
         }

egui_web/CHANGELOG.md

@@ -10,6 +10,7 @@ All notable changes to the `egui_web` integration will be noted in this file.
 * Shift-scroll will now result in horizontal scrolling ([#1136](https://github.com/emilk/egui/pull/1136)).
 * Updated `epi::IntegrationInfo::web_location_hash` on `hashchange` event ([#1140](https://github.com/emilk/egui/pull/1140)).
 * Panics will now be logged using `console.error`.
+* Parse and percent-decode the web location query string ([#1258](https://github.com/emilk/egui/pull/1258)).
 
 
 ## 0.16.0 - 2021-12-29

egui_web/Cargo.toml

@@ -57,6 +57,7 @@ epi = { version = "0.16.0", path = "../epi" }
 
 bytemuck = "1.7"
 js-sys = "0.3"
+percent-encoding = "2.1"
 tracing = "0.1"
 wasm-bindgen = "0.2"
 wasm-bindgen-futures = "0.4"

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())?;

epi/src/lib.rs

@@ -361,10 +361,62 @@ impl Frame {
 /// Information about the web environment (if applicable).
 #[derive(Clone, Debug)]
 pub struct WebInfo {
-    /// e.g. "#fragment" part of "www.example.com/index.html#fragment".
+    /// Information about the URL.
+    pub location: Location,
+}
+
+/// Information about the URL.
+///
+/// Everything has been percent decoded (`%20` -> ` ` etc).
+#[derive(Clone, Debug)]
+pub struct Location {
+    /// The full URL (`location.href`) without the hash.
+    ///
+    /// Example: "http://www.example.com:80/index.html?foo=bar".
+    pub url: String,
+
+    /// `location.protocol`
+    ///
+    /// Example: "http:".
+    pub protocol: String,
+
+    /// `location.host`
+    ///
+    /// Example: "example.com:80".
+    pub host: String,
+
+    /// `location.hostname`
+    ///
+    /// Example: "example.com".
+    pub hostname: String,
+
+    /// `location.port`
+    ///
+    /// Example: "80".
+    pub port: String,
+
+    /// The "#fragment" part of "www.example.com/index.html?query#fragment".
+    ///
     /// Note that the leading `#` is included in the string.
     /// Also known as "hash-link" or "anchor".
-    pub web_location_hash: String,
+    pub hash: String,
+
+    /// The "query" part of "www.example.com/index.html?query#fragment".
+    ///
+    /// Note that the leading `?` is NOT included in the string.
+    ///
+    /// Use [`Self::web_query_map]` to get the parsed version of it.
+    pub query: String,
+
+    /// The parsed "query" part of "www.example.com/index.html?query#fragment".
+    ///
+    /// "foo=42&bar%20" is parsed as `{"foo": "42",  "bar ": ""}`
+    pub query_map: std::collections::BTreeMap<String, String>,
+
+    /// `location.origin`
+    ///
+    /// Example: "http://www.example.com:80"
+    pub origin: String,
 }
 
 /// Information about the integration passed to the use app each frame.