Added ability to drag dialogs to search field.

Telegram/SourceFiles/dialogs/dialogs_widget.cpp

@@ -27,6 +27,7 @@ https://github.com/telegramdesktop/tdesktop/blob/master/LEGAL
 #include "history/view/history_view_requests_bar.h"
 #include "history/view/history_view_top_bar_widget.h"
 #include "boxes/peers/edit_peer_requests_box.h"
+#include "boxes/choose_filter_box.h"
 #include "ui/text/text_utilities.h"
 #include "ui/widgets/buttons.h"
 #include "ui/widgets/chat_filters_tabs_strip.h"
@@ -550,6 +551,20 @@ Widget::Widget(
 	_search->submits(
 	) | rpl::on_next([=] { submit(); }, _search->lifetime());
 
+	_search->setMimeDataHook([=](
+			not_null<const QMimeData*> data,
+			Ui::InputField::MimeAction action) {
+		if (data->hasFormat(u"application/x-telegram-dialog"_q)) {
+			if (const auto history = HistoryFromMimeData(data, &session())) {
+				if (action != Ui::InputField::MimeAction::Check) {
+					controller->searchInChat(history);
+				}
+				return true;
+			}
+		}
+		return false;
+	});
+
 	QObject::connect(
 		_search->rawTextEdit().get(),
 		&QTextEdit::cursorPositionChanged,