From 4a00a6ac2ccbf4c9b660ec90e411b709875cb59c Mon Sep 17 00:00:00 2001
From: SGavrl <277843151+SGavrl@users.noreply.github.com>
Date: Tue, 9 Jun 2026 21:21:51 +0000
Subject: [PATCH] Implement DOM.focus for keyboard input (#283)

CDP clients (browser-use and similar) focus an input via DOM.focus before
typing; Input.dispatchKeyEvent then targets document.activeElement. Without a
DOM.focus handler the focus call errored, keystrokes landed on nothing, and the
field stayed empty. Resolve the node and call its JS focus(), which sets
document.activeElement. Completes the type path for DOM-agent frameworks.
---
 crates/obscura-cdp/src/domains/dom.rs | 61 +++++++++++++++++++++++++++
 1 file changed, 61 insertions(+)

diff --git a/crates/obscura-cdp/src/domains/dom.rs b/crates/obscura-cdp/src/domains/dom.rs
index fb2f4aa..53034b2 100644
--- a/crates/obscura-cdp/src/domains/dom.rs
+++ b/crates/obscura-cdp/src/domains/dom.rs
@@ -165,6 +165,21 @@ pub async fn handle(
         }
         "setAttributeValue" => Ok(json!({})),
         "removeNode" => Ok(json!({})),
+        "focus" => {
+            // No layout engine, but obscura's JS focus() sets document.activeElement,
+            // which Input.dispatchKeyEvent targets. CDP clients (browser-use) focus an
+            // input via DOM.focus before typing; without this their keystrokes land on
+            // nothing and the field stays empty.
+            let page = ctx.get_session_page_mut(session_id).ok_or("No page")?;
+            let node_id = resolve_node_id(page, params)?;
+            let code = format!(
+                "(function() {{ var el = globalThis._wrap && globalThis._wrap({0}); \
+                 if (el && typeof el.focus === 'function') {{ el.focus(); return true; }} return false; }})()",
+                node_id
+            );
+            let _ = page.evaluate(&code);
+            Ok(json!({}))
+        }
         "getBoxModel" => {
             let page = ctx.get_session_page_mut(session_id).ok_or("No page")?;
             let node_id = match resolve_node_id(page, params) {
@@ -282,3 +297,49 @@ fn serialize_node(dom: &DomTree, node_id: NodeId, max_depth: u32, current_depth:
     }
     result
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use crate::dispatch::CdpContext;
+
+    #[tokio::test]
+    async fn dom_focus_sets_active_element() {
+        // CDP clients (browser-use) focus an input via DOM.focus before typing;
+        // dispatchKeyEvent then targets document.activeElement. DOM.focus must
+        // actually move focus or keystrokes land on nothing.
+        let mut ctx = CdpContext::new();
+        let page_id = ctx.create_page();
+        let session = Some(format!("{page_id}-session"));
+        ctx.sessions.insert(session.clone().unwrap(), page_id.clone());
+
+        crate::domains::page::handle(
+            "navigate",
+            &json!({ "url": "data:text/html,<input id=q>", "waitUntil": "load" }),
+            &mut ctx,
+            &session,
+        )
+        .await
+        .expect("navigate should succeed");
+
+        let qs = handle("querySelector", &json!({ "selector": "input" }), &mut ctx, &session)
+            .await
+            .expect("querySelector should succeed");
+        let nid = qs["nodeId"].as_u64().expect("input nodeId");
+        assert!(nid > 0, "the input element should be found");
+
+        handle("focus", &json!({ "nodeId": nid }), &mut ctx, &session)
+            .await
+            .expect("DOM.focus should succeed");
+
+        let active = ctx
+            .get_session_page_mut(&session)
+            .unwrap()
+            .evaluate("(function(){return document.activeElement?document.activeElement.tagName:'NONE';})()");
+        assert_eq!(
+            active,
+            json!("INPUT"),
+            "DOM.focus must set document.activeElement to the focused input"
+        );
+    }
+}