LibWeb: Implement BrowsingContext::selected_text() in terms of Selection

Instead of sifting through the layout tree to extract the selected text,
look at the DOM selection instead.

Note that we can't just stringify the DOM Range, as that would include
non-visible things (like the content of <style> elements, etc.) so we
run it through an ad-hoc variant of the range stringification algorithm.
This can probably be factored better, but it's a start. :^)

1 files changed, 26 insertions, 35 deletions

diff --git a/Userland/Libraries/LibWeb/HTML/BrowsingContext.cpp b/Userland/Libraries/LibWeb/HTML/BrowsingContext.cpp
index e0b3c365c0..d25709cf2c 100644
--- a/Userland/Libraries/LibWeb/HTML/BrowsingContext.cpp
+++ b/Userland/Libraries/LibWeb/HTML/BrowsingContext.cpp
@@ -8,6 +8,7 @@
 #include <LibWeb/DOM/Document.h>
 #include <LibWeb/DOM/Event.h>
 #include <LibWeb/DOM/HTMLCollection.h>
+#include <LibWeb/DOM/Range.h>
 #include <LibWeb/Fetch/Infrastructure/HTTP/Requests.h>
 #include <LibWeb/HTML/BrowsingContext.h>
 #include <LibWeb/HTML/BrowsingContextContainer.h>
@@ -468,53 +469,43 @@ void BrowsingContext::set_cursor_position(DOM::Position position)
     reset_cursor_blink_cycle();
 }
 
-DeprecatedString BrowsingContext::selected_text() const
+static DeprecatedString 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.
     StringBuilder builder;
-    if (!active_document())
-        return {};
-    auto* layout_root = active_document()->layout_node();
-    if (!layout_root)
-        return {};
-    if (!layout_root->selection().is_valid())
-        return {};
 
-    auto selection = layout_root->selection().normalized();
-
-    if (selection.start().layout_node.ptr() == selection.end().layout_node) {
-        if (!is<Layout::TextNode>(*selection.start().layout_node))
-            return "";
-        return verify_cast<Layout::TextNode>(*selection.start().layout_node).text_for_rendering().substring(selection.start().index_in_node, selection.end().index_in_node - selection.start().index_in_node);
+    if (range.start_container() == range.end_container() && is<DOM::Text>(*range.start_container())) {
+        if (!range.start_container()->layout_node())
+            return ""sv;
+        return static_cast<DOM::Text const&>(*range.start_container()).data().substring(range.start_offset(), range.end_offset() - range.start_offset());
     }
 
-    // Start node
-    auto layout_node = selection.start().layout_node;
-    if (is<Layout::TextNode>(*layout_node)) {
-        auto& text = verify_cast<Layout::TextNode>(*layout_node).text_for_rendering();
-        builder.append(text.substring(selection.start().index_in_node, text.length() - selection.start().index_in_node));
-    }
+    if (is<DOM::Text>(*range.start_container()) && range.start_container()->layout_node())
+        builder.append(static_cast<DOM::Text const&>(*range.start_container()).data().substring_view(range.start_offset()));
 
-    // Middle nodes
-    layout_node = layout_node->next_in_pre_order();
-    while (layout_node && layout_node.ptr() != selection.end().layout_node) {
-        if (is<Layout::TextNode>(*layout_node))
-            builder.append(verify_cast<Layout::TextNode>(*layout_node).text_for_rendering());
-        else if (is<Layout::BreakNode>(*layout_node) || is<Layout::BlockContainer>(*layout_node))
-            builder.append('\n');
-
-        layout_node = layout_node->next_in_pre_order();
+    for (DOM::Node const* node = range.start_container(); node != range.end_container()->next_sibling(); node = node->next_in_pre_order()) {
+        if (is<DOM::Text>(*node) && range.contains_node(*node) && node->layout_node())
+            builder.append(static_cast<DOM::Text const&>(*node).data());
     }
 
-    // End node
-    VERIFY(layout_node.ptr() == selection.end().layout_node);
-    if (is<Layout::TextNode>(*layout_node)) {
-        auto& text = verify_cast<Layout::TextNode>(*layout_node).text_for_rendering();
-        builder.append(text.substring(0, selection.end().index_in_node));
-    }
+    if (is<DOM::Text>(*range.end_container()) && range.end_container()->layout_node())
+        builder.append(static_cast<DOM::Text const&>(*range.end_container()).data().substring_view(0, range.end_offset()));
 
     return builder.to_deprecated_string();
 }
 
+DeprecatedString BrowsingContext::selected_text() const
+{
+    auto* document = active_document();
+    if (!document)
+        return ""sv;
+    auto selection = const_cast<DOM::Document&>(*document).get_selection();
+    auto range = selection->range();
+    if (!range)
+        return ""sv;
+    return visible_text_in_range(*range);
+}
+
 void BrowsingContext::select_all()
 {
     if (!active_document())