From 0b9911b2e6302c89b73e5c07bb77a2bb1dd85e8c Mon Sep 17 00:00:00 2001
From: jprochazk <1665677+jprochazk@users.noreply.github.com>
Date: Wed, 29 May 2024 12:32:30 +0200
Subject: [PATCH] docs for `focused_element` + add `has_focus` helper

---
 crates/eframe/src/web/mod.rs        | 22 +++++++++++++++++++---
 crates/eframe/src/web/text_agent.rs |  3 +--
 2 files changed, 20 insertions(+), 5 deletions(-)

diff --git a/crates/eframe/src/web/mod.rs b/crates/eframe/src/web/mod.rs
index 1963795f126..e5cdab9ad7d 100644
--- a/crates/eframe/src/web/mod.rs
+++ b/crates/eframe/src/web/mod.rs
@@ -53,11 +53,27 @@ pub(crate) fn string_from_js_value(value: &JsValue) -> String {
     value.as_string().unwrap_or_else(|| format!("{value:#?}"))
 }
 
-pub(crate) fn focused_element() -> Option<web_sys::HtmlElement> {
+/// Returns the `Element` with active focus.
+///
+/// Elements can only be focused if they are:
+/// - `<a>`/`<area>` with an `href` attribute
+/// - `<input>`/`<select>`/`<textarea>`/`<button>` which aren't `disabled`
+/// - any other element with a `tabindex` attribute
+pub(crate) fn focused_element() -> Option<web_sys::Element> {
     web_sys::window()?
         .document()?
-        .active_element()
-        .and_then(|v| v.dyn_into().ok())
+        .active_element()?
+        .dyn_into()
+        .ok()
+}
+
+pub(crate) fn has_focus<T: Clone + JsCast>(element: &T) -> bool {
+    fn inner<T: Clone + JsCast>(element: &T) -> Option<bool> {
+        let element = element.dyn_ref::<web_sys::Element>()?;
+        let focused_element = focused_element()?;
+        Some(element == &focused_element)
+    }
+    inner(element).unwrap_or(false)
 }
 
 /// Current time in seconds (since undefined point in time).
diff --git a/crates/eframe/src/web/text_agent.rs b/crates/eframe/src/web/text_agent.rs
index 264a3e3dafb..d723096b739 100644
--- a/crates/eframe/src/web/text_agent.rs
+++ b/crates/eframe/src/web/text_agent.rs
@@ -134,8 +134,7 @@ impl TextAgent {
     }
 
     pub fn has_focus(&self) -> bool {
-        let active_element = super::focused_element();
-        self.input.clone().dyn_into().ok() == active_element
+        super::has_focus(&self.input)
     }
 
     fn focus(&self) {