LibWeb: Implement DataTransfer.prototype.getData()

This is used by Google Lens. It will always return the empty string when
dragging an image onto the Google Lens search field.

Userland/Libraries/LibWeb/HTML/DataTransfer.cpp

@@ -4,6 +4,7 @@
  * SPDX-License-Identifier: BSD-2-Clause
  */
 
+#include <AK/Find.h>
 #include <LibJS/Runtime/Realm.h>
 #include <LibWeb/Bindings/DataTransferPrototype.h>
 #include <LibWeb/Bindings/Intrinsics.h>
@@ -11,6 +12,7 @@
 #include <LibWeb/FileAPI/File.h>
 #include <LibWeb/FileAPI/FileList.h>
 #include <LibWeb/HTML/DataTransfer.h>
+#include <LibWeb/Infra/Strings.h>
 
 namespace Web::HTML {
 
@@ -87,6 +89,56 @@ ReadonlySpan<String> DataTransfer::types() const
     return m_types;
 }
 
+// https://html.spec.whatwg.org/multipage/dnd.html#dom-datatransfer-getdata
+String DataTransfer::get_data(String const& format_argument) const
+{
+    // 1. If the DataTransfer object is no longer associated with a drag data store, then return the empty string.
+    if (!m_associated_drag_data_store.has_value())
+        return {};
+
+    // 2. If the drag data store's mode is the protected mode, then return the empty string.
+    if (m_associated_drag_data_store->mode() == DragDataStore::Mode::Protected)
+        return {};
+
+    // 3. Let format be the first argument, converted to ASCII lowercase.
+    auto format = MUST(Infra::to_ascii_lowercase(format_argument));
+
+    // 4. Let convert-to-URL be false.
+    [[maybe_unused]] bool convert_to_url = false;
+
+    // 5. If format equals "text", change it to "text/plain".
+    if (format == "text"sv) {
+        format = "text/plain"_string;
+    }
+
+    // 6. If format equals "url", change it to "text/uri-list" and set convert-to-URL to true.
+    else if (format == "url"sv) {
+        format = "text/uri-list"_string;
+        convert_to_url = true;
+    }
+
+    // 7. If there is no item in the drag data store item list whose kind is text and whose type string is equal to
+    //    format, return the empty string.
+    auto item_list = m_associated_drag_data_store->item_list();
+
+    auto it = find_if(item_list.begin(), item_list.end(), [&](auto const& item) {
+        return item.kind == DragDataStoreItem::Kind::Text && item.type_string == format;
+    });
+
+    if (it == item_list.end())
+        return {};
+
+    // 8. Let result be the data of the item in the drag data store item list whose kind is Plain Unicode string and
+    //    whose type string is equal to format.
+    auto const& result = it->data;
+
+    // FIXME: 9. If convert-to-URL is true, then parse result as appropriate for text/uri-list data, and then set result to
+    //           the first URL from the list, if any, or the empty string otherwise.
+
+    // 10. Return result.
+    return MUST(String::from_utf8(result));
+}
+
 // https://html.spec.whatwg.org/multipage/dnd.html#dom-datatransfer-files
 JS::NonnullGCPtr<FileAPI::FileList> DataTransfer::files() const
 {

Userland/Libraries/LibWeb/HTML/DataTransfer.h

@@ -50,7 +50,7 @@ public:
     void set_effect_allowed_internal(FlyString);
 
     ReadonlySpan<String> types() const;
-
+    String get_data(String const& format) const;
     JS::NonnullGCPtr<FileAPI::FileList> files() const;
 
     void associate_with_drag_data_store(DragDataStore& drag_data_store);

Userland/Libraries/LibWeb/HTML/DataTransfer.idl

@@ -14,7 +14,7 @@ interface DataTransfer {
 
     // old interface
     readonly attribute sequence<DOMString> types; // FIXME: This should be FrozenArray<DOMString>
-    [FIXME] DOMString getData(DOMString format);
+    DOMString getData(DOMString format);
     [FIXME] undefined setData(DOMString format, DOMString data);
     [FIXME] undefined clearData(optional DOMString format);
     [SameObject] readonly attribute FileList files;