LibWeb: Implement DataTransferItemList.clear()

Author: https://github.com/tcl3
Commit: 3fc7613bf1
Pull-request: https://github.com/LadybirdBrowser/ladybird/pull/6088
Reviewed-by: https://github.com/gmta

Libraries/LibWeb/HTML/DataTransferItemList.cpp

@@ -125,6 +125,15 @@ WebIDL::ExceptionOr<void> DataTransferItemList::remove(WebIDL::UnsignedLong inde
     return {};
 }
 
+// https://html.spec.whatwg.org/multipage/dnd.html#dom-datatransferitemlist-clear
+void DataTransferItemList::clear()
+{
+    // The clear() method, if the DataTransferItemList object is in the read/write mode, must remove all the items from
+    // the drag data store. Otherwise, it must do nothing.
+    if (m_data_transfer->mode() == DragDataStore::Mode::ReadWrite)
+        m_data_transfer->clear_data();
+}
+
 // https://html.spec.whatwg.org/multipage/dnd.html#dom-datatransferitemlist-item
 Optional<JS::Value> DataTransferItemList::item_value(size_t index) const
 {

Libraries/LibWeb/HTML/DataTransferItemList.h

@@ -27,6 +27,7 @@ public:
     WebIDL::ExceptionOr<GC::Ptr<DataTransferItem>> add(String const& data, String const& type);
     GC::Ptr<DataTransferItem> add(GC::Ref<FileAPI::File>);
     WebIDL::ExceptionOr<void> remove(WebIDL::UnsignedLong index);
+    void clear();
 
 private:
     DataTransferItemList(JS::Realm&, GC::Ref<DataTransfer>);

Libraries/LibWeb/HTML/DataTransferItemList.idl

@@ -9,5 +9,5 @@ interface DataTransferItemList {
     DataTransferItem? add(DOMString data, DOMString type);
     DataTransferItem? add(File data);
     undefined remove(unsigned long index);
-    [FIXME] undefined clear();
+    undefined clear();
 };