diff --git a/src/webenginewidgets/render_widget_host_view_qt_delegate_widget.h b/src/webenginewidgets/render_widget_host_view_qt_delegate_widget.h
index ab24b1e4123044355351a9fa6e17476e68100153..42b454bc5dfccb7ceb9538eaeb582e61af8ba9c1 100644
--- a/src/webenginewidgets/render_widget_host_view_qt_delegate_widget.h
+++ b/src/webenginewidgets/render_widget_host_view_qt_delegate_widget.h
@@ -48,6 +48,12 @@
 
 namespace QtWebEngineCore {
 
+// Useful information keyboard and mouse QEvent propagation.
+// A RenderWidgetHostViewQtDelegateWidget instance initialized as a popup will receive
+// no keyboard focus (so all keyboard QEvents will be sent to the parent RWHVQD instance),
+// but will still receive mouse input (all mouse QEvent moves and clicks will be given to the popup
+// RWHVQD instance, and the mouse interaction area covers the surface of the whole parent
+// QWebEngineView, and not only the smaller surface that an HTML select popup would occupy).
 class RenderWidgetHostViewQtDelegateWidget : public QQuickWidget, public RenderWidgetHostViewQtDelegate {
     Q_OBJECT
 public: