Fix idling? blocking on lazy iframes that Chrome never loads

agrberg · agrberg · commit 7ef14d62555f · 2026-05-17T12:48:37.000-04:00
Chrome fires Page.frameAttached for every iframe in the DOM, but only fires Page.frameStoppedLoading for frames it actually loads. For a loading="lazy" iframe parked outside the viewport (e.g. inside a closed <details>), Chrome never starts loading it, so it never transitions to :started_loading or :stopped_loading. It stays at state nil indefinitely. The previous idling? required every frame to be :stopped_loading, which meant any lazy iframe blocked idle detection for the full browser timeout (default 5s). Treat freshly-attached frames (state nil) as idle too — they haven't started loading, so there's nothing to wait for. Fixes #583
diff --git a/CHANGELOG.md b/CHANGELOG.md
@@ -6,6 +6,7 @@
 
 ### Fixed
 - Full-page screenshots no longer resize the window, preventing focus steal on macOS [#580]
+- `idling?` no longer blocks for the full browser timeout when a page contains a `loading="lazy"` iframe that Chrome never starts loading [#583]
 
 ### Removed
 
diff --git a/lib/ferrum/page/frames.rb b/lib/ferrum/page/frames.rb
@@ -191,7 +191,7 @@ def subscribe_execution_contexts_cleared
       end
 
       def idling?
-        @frames.values.all? { |f| f.state == :stopped_loading }
+        @frames.values.all? { |f| f.state.nil? || f.state == :stopped_loading }
       end
     end
   end
diff --git a/spec/frame_spec.rb b/spec/frame_spec.rb
@@ -125,6 +125,17 @@
     end
   end
 
+  context "with loading=lazy iframe" do
+    it "does not block idle detection when Chrome never loads the iframe" do
+      started_at = Process.clock_gettime(Process::CLOCK_MONOTONIC)
+      page.go_to("/lazy_iframe")
+      elapsed = Process.clock_gettime(Process::CLOCK_MONOTONIC) - started_at
+
+      expect(elapsed).to be < 2.0
+      expect(page.body).to include("Lazy iframe")
+    end
+  end
+
   it "supports clicking in a frame", skip: true do
     page.go_to
     page.execute <<-JS
diff --git a/spec/support/views/lazy_iframe.erb b/spec/support/views/lazy_iframe.erb
@@ -0,0 +1,14 @@
+<!DOCTYPE html>
+<html>
+  <head>
+    <title>Lazy iframe</title>
+  </head>
+  <body>
+    <h1>Lazy iframe</h1>
+
+    <details>
+      <summary>Hidden until expanded</summary>
+      <iframe loading="lazy" src="/slow" name="lazy_frame"></iframe>
+    </details>
+  </body>
+</html>
