LibWeb: Skip user-select:none when extracting selected text

Problem: Select All (Ctrl+A or the context menu) followed by Ctrl+C
unexpectedly copies text from elements with user-select:none — breaking
compat with Chrome and Firefox, which both exclude user-select:none
content from the clipboard.

Cause: Navigable::selected_text() walks the selection range via
visible_text_in_range() and concatenates each text node’s data. The walk
filters out nodes without a layout, but not nodes whose used value of
user-select is ‘none’.

Fix: Add a user-select check at each visible_text_in_range() walk point.
The Selection range itself is left unchanged. Selection.toString() still
returns the full text per spec — but the clipboard-extraction path now
excludes user-select: none subtrees, per spec

Author: sideshowbarker

Libraries/LibWeb/HTML/Navigable.cpp

@@ -3241,25 +3241,32 @@ bool Navigable::is_focused() const
 
 static String visible_text_in_range(DOM::Range const& range)
 {
-    // NOTE: This is an adaption of Range stringification, but we skip over DOM nodes that don't have a corresponding layout node.
+    // NOTE: This is an adaption of Range stringification — but we skip over DOM nodes that don't have a corresponding
+    //       layout node, and over nodes whose used value of user-select is 'none'. The latter implements
+    //       https://drafts.csswg.org/css-ui/#valdef-user-select-none — applied at the clipboard-extraction boundary.
     StringBuilder builder;
 
+    auto is_user_select_none = [](DOM::Node const& node) {
+        auto const* layout = node.layout_node();
+        return layout && layout->user_select_used_value() == CSS::UserSelect::None;
+    };
+
     if (range.start_container() == range.end_container() && is<DOM::Text>(*range.start_container())) {
-        if (!range.start_container()->layout_node())
+        if (!range.start_container()->layout_node() || is_user_select_none(*range.start_container()))
             return String {};
         return static_cast<DOM::Text const&>(*range.start_container()).data().substring_view(range.start_offset(), range.end_offset() - range.start_offset()).to_utf8_but_should_be_ported_to_utf16();
     }
 
-    if (is<DOM::Text>(*range.start_container()) && range.start_container()->layout_node())
+    if (is<DOM::Text>(*range.start_container()) && range.start_container()->layout_node() && !is_user_select_none(*range.start_container()))
         builder.append(static_cast<DOM::Text const&>(*range.start_container()).data().substring_view(range.start_offset()));
 
     range.for_each_contained([&](GC::Ref<DOM::Node> node) {
-        if (is<DOM::Text>(*node) && node->layout_node())
+        if (is<DOM::Text>(*node) && node->layout_node() && !is_user_select_none(*node))
             builder.append(static_cast<DOM::Text const&>(*node).data());
         return IterationDecision::Continue;
     });
 
-    if (is<DOM::Text>(*range.end_container()) && range.end_container()->layout_node())
+    if (is<DOM::Text>(*range.end_container()) && range.end_container()->layout_node() && !is_user_select_none(*range.end_container()))
         builder.append(static_cast<DOM::Text const&>(*range.end_container()).data().substring_view(0, range.end_offset()));
 
     return MUST(builder.to_string());

Libraries/LibWeb/Internals/Internals.cpp

@@ -410,6 +410,11 @@ String Internals::current_cursor()
         });
 }
 
+String Internals::selected_text_for_clipboard()
+{
+    return page().focused_navigable().selected_text();
+}
+
 WebIDL::ExceptionOr<bool> Internals::dispatch_user_activated_event(DOM::EventTarget& target, DOM::Event& event)
 {
     event.set_is_trusted(true);

Libraries/LibWeb/Internals/Internals.h

@@ -70,6 +70,8 @@ class WEB_API Internals final : public InternalsBase {
 
     String current_cursor();
 
+    String selected_text_for_clipboard();
+
     WebIDL::ExceptionOr<bool> dispatch_user_activated_event(DOM::EventTarget&, DOM::Event& event);
 
     void spoof_current_url(String const& url);

Libraries/LibWeb/Internals/Internals.idl

@@ -45,6 +45,10 @@ interface Internals {
 
     DOMString currentCursor();
 
+    // Returns the text that would be placed on the clipboard if the user copied the current selection now.
+    // Excludes nodes whose used value of user-select is 'none' — mirroring what browsers actually copy.
+    DOMString selectedTextForClipboard();
+
     boolean dispatchUserActivatedEvent(EventTarget target, Event event);
     undefined spoofCurrentURL(USVString url);
 

Tests/LibWeb/Text/expected/select-all-respects-user-select-none.txt

@@ -0,0 +1,2 @@
+selection.toString(): "hiddenvisiblealso hiddenalso visible"
+clipboard text: "visiblealso visible"

Tests/LibWeb/Text/input/select-all-respects-user-select-none.html

@@ -0,0 +1,16 @@
+<!DOCTYPE html>
+<script src="include.js"></script>
+<div id="container"><p style="user-select: none;">hidden</p><p>visible</p><p style="user-select: none;">also hidden</p><p>also visible</p></div>
+<script>
+    test(() => {
+        getSelection().selectAllChildren(document.getElementById("container"));
+
+        // Per the Selection API spec, the Range itself still spans the whole container, including user-select:none
+        // subtrees — so Selection.toString() returns everything.
+        println(`selection.toString(): "${getSelection().toString().replace(/\n/g, "\\n")}"`);
+
+        // But the clipboard/visible-selection path must exclude user-select: none content, per
+        // https://drafts.csswg.org/css-ui/#valdef-user-select-none.
+        println(`clipboard text: "${internals.selectedTextForClipboard().replace(/\n/g, "\\n")}"`);
+    });
+</script>