LibWeb: Update input/textarea selection on document selection change

This causes UI interactions with the document selection to also update
the input and textarea DOM selection state.

Userland/Libraries/LibWeb/Page/EventHandler.cpp

@@ -10,12 +10,14 @@
 #include <LibWeb/HTML/BrowsingContext.h>
 #include <LibWeb/HTML/CloseWatcherManager.h>
 #include <LibWeb/HTML/Focus.h>
+#include <LibWeb/HTML/FormAssociatedElement.h>
 #include <LibWeb/HTML/HTMLAnchorElement.h>
 #include <LibWeb/HTML/HTMLFormElement.h>
 #include <LibWeb/HTML/HTMLIFrameElement.h>
 #include <LibWeb/HTML/HTMLImageElement.h>
 #include <LibWeb/HTML/HTMLInputElement.h>
 #include <LibWeb/HTML/HTMLMediaElement.h>
+#include <LibWeb/HTML/HTMLTextAreaElement.h>
 #include <LibWeb/HTML/HTMLVideoElement.h>
 #include <LibWeb/Layout/Viewport.h>
 #include <LibWeb/Page/DragAndDropEventHandler.h>
@@ -472,6 +474,7 @@ bool EventHandler::handle_mousedown(CSSPixelPoint viewport_position, CSSPixelPoi
                             (void)selection->set_base_and_extent(*dom_node, result->index_in_node, *dom_node, result->index_in_node);
                         }
                     }
+                    update_selection_range_for_input_or_textarea();
                     m_in_mouse_selection = true;
                 }
             }
@@ -593,6 +596,7 @@ bool EventHandler::handle_mousemove(CSSPixelPoint viewport_position, CSSPixelPoi
                 if (should_set_cursor_position)
                     document.set_cursor_position(DOM::Position::create(realm, *hit->dom_node(), *start_index));
 
+                update_selection_range_for_input_or_textarea();
                 document.set_needs_display();
             }
         }
@@ -716,6 +720,7 @@ bool EventHandler::handle_doubleclick(CSSPixelPoint viewport_position, CSSPixelP
             if (auto selection = node->document().get_selection()) {
                 (void)selection->set_base_and_extent(hit_dom_node, first_word_break_before, hit_dom_node, first_word_break_after);
             }
+            update_selection_range_for_input_or_textarea();
         }
     }
 
@@ -988,6 +993,8 @@ bool EventHandler::handle_keydown(UIEvents::KeyCode key, u32 modifiers, u32 code
         }
     }
 
+    update_selection_range_for_input_or_textarea();
+
     // FIXME: Implement scroll by line and by page instead of approximating the behavior of other browsers.
     auto arrow_key_scroll_distance = 100;
     auto page_scroll_distance = document->window()->inner_height() - (document->window()->outer_height() - document->window()->inner_height());
@@ -1123,4 +1130,53 @@ void EventHandler::visit_edges(JS::Cell::Visitor& visitor) const
     visitor.visit(m_mouse_event_tracking_paintable);
 }
 
+// https://html.spec.whatwg.org/multipage/form-control-infrastructure.html#textFieldSelection:set-the-selection-range
+void EventHandler::update_selection_range_for_input_or_textarea()
+{
+    // Where possible, user interface features for changing the text selection in input and
+    // textarea elements must be implemented using the set the selection range algorithm so that,
+    // e.g., all the same events fire.
+
+    // NOTE: It seems like only new selections are registered with the respective elements. I.e.
+    //       existing selections in other elements are not cleared, so we only need to set the
+    //       selection range for the element with the current selection.
+
+    // Get the active selection
+    auto active_document = m_navigable->active_document();
+    if (!active_document)
+        return;
+    auto selection = active_document->get_selection();
+    if (!selection)
+        return;
+
+    // Do we have a range within the same node?
+    auto range = selection->range();
+    if (!range || range->start_container() != range->end_container())
+        return;
+
+    // We are only interested in text nodes with a shadow root
+    auto& node = *range->start_container();
+    if (!node.is_text())
+        return;
+    auto& root = node.root();
+    if (!root.is_shadow_root())
+        return;
+    auto& shadow_host = *root.parent_or_shadow_host();
+
+    // Invoke "set the selection range" on the form associated element
+    auto selection_start = range->start_offset();
+    auto selection_end = range->end_offset();
+    // FIXME: support selection directions other than ::Forward
+    auto direction = HTML::SelectionDirection::Forward;
+
+    Optional<HTML::FormAssociatedElement&> target {};
+    if (is<HTML::HTMLInputElement>(shadow_host))
+        target = static_cast<HTML::HTMLInputElement&>(shadow_host);
+    else if (is<HTML::HTMLTextAreaElement>(shadow_host))
+        target = static_cast<HTML::HTMLTextAreaElement&>(shadow_host);
+
+    if (target.has_value())
+        target.value().set_the_selection_range(selection_start, selection_end, direction);
+}
+
 }

Userland/Libraries/LibWeb/Page/EventHandler.h

@@ -60,6 +60,7 @@ class EventHandler {
     Painting::PaintableBox const* paint_root() const;
 
     bool should_ignore_device_input_event() const;
+    void update_selection_range_for_input_or_textarea();
 
     JS::NonnullGCPtr<HTML::Navigable> m_navigable;