LibWeb: Return the same DataTransfer.types() array if unmodified

Author: https://github.com/tcl3
Commit: 3099459504
Pull-request: https://github.com/LadybirdBrowser/ladybird/pull/6088
Reviewed-by: https://github.com/gmta

Libraries/LibWeb/HTML/DataTransfer.cpp

@@ -74,6 +74,8 @@ void DataTransfer::visit_edges(JS::Cell::Visitor& visitor)
     Base::visit_edges(visitor);
     visitor.visit(m_items);
     visitor.visit(m_item_list);
+
+    VISIT_CACHED_ATTRIBUTE(types);
 }
 
 void DataTransfer::set_drop_effect(String const& drop_effect)
@@ -374,6 +376,7 @@ void DataTransfer::update_data_transfer_types_list()
     }
 
     // 3. Set the DataTransfer object's types array to the result of creating a frozen array from L.
+    set_cached_types(nullptr);
     m_types = move(types);
 }
 

Libraries/LibWeb/HTML/DataTransfer.h

@@ -9,6 +9,7 @@
 #include <LibJS/Forward.h>
 #include <LibWeb/Bindings/PlatformObject.h>
 #include <LibWeb/HTML/DragDataStore.h>
+#include <LibWeb/WebIDL/CachedAttribute.h>
 
 namespace Web::HTML {
 
@@ -53,6 +54,7 @@ public:
     GC::Ref<DataTransferItemList> items();
 
     ReadonlySpan<String> types() const;
+    DEFINE_CACHED_ATTRIBUTE(types);
     String get_data(String const& format) const;
     void clear_data(Optional<String> maybe_format = {});
     GC::Ref<FileAPI::FileList> files() const;

Libraries/LibWeb/HTML/DataTransfer.idl

@@ -14,7 +14,7 @@ interface DataTransfer {
     [FIXME] undefined setDragImage(Element image, long x, long y);
 
     // old interface
-    readonly attribute FrozenArray<DOMString> types;
+    [CachedAttribute] readonly attribute FrozenArray<DOMString> types;
     DOMString getData(DOMString format);
     [FIXME] undefined setData(DOMString format, DOMString data);
     undefined clearData(optional DOMString format);