Implement drag-n-drop to forum topics.

Telegram/SourceFiles/window/section_widget.h

@@ -151,6 +151,13 @@ public:
 		return SectionActionResult::Ignore;
 	}
 
+	virtual bool confirmSendingFiles(const QStringList &files) {
+		return false;
+	}
+	virtual bool confirmSendingFiles(not_null<const QMimeData*> data) {
+		return false;
+	}
+
 	// Create a memento of that section to store it in the history stack.
 	// This method may modify the section ("take" heavy items).
 	virtual std::shared_ptr<SectionMemento> createMemento();

Telegram/SourceFiles/window/window_peer_menu.cpp

@@ -1542,20 +1542,20 @@ QPointer<Ui::BoxContent> ShowForwardMessagesBox(
 		std::move(successCallback));
 }
 
-QPointer<Ui::BoxContent> ShowForwardMessagesBox(
+QPointer<Ui::BoxContent> ShowDropMediaBox(
 		not_null<Window::SessionNavigation*> navigation,
-		Data::ForwardDraft &&draft,
+		std::shared_ptr<QMimeData> data,
 		not_null<Data::Forum*> forum,
 		FnMut<void()> &&successCallback) {
 	const auto weak = std::make_shared<QPointer<Ui::BoxContent>>();
 	auto chosen = [
-		draft = std::move(draft),
+		data = std::move(data),
 		callback = std::move(successCallback),
 		weak,
 		navigation
 	](not_null<Data::ForumTopic*> topic) mutable {
 		const auto content = navigation->parentController()->content();
-		if (!content->setForwardDraft(topic, std::move(draft))) {
+		if (!content->onFilesOrForwardDrop(topic, data.get())) {
 			return;
 		} else if (const auto strong = *weak) {
 			strong->closeBox();

Telegram/SourceFiles/window/window_peer_menu.h

@@ -122,9 +122,9 @@ QPointer<Ui::BoxContent> ShowForwardMessagesBox(
 	not_null<Window::SessionNavigation*> navigation,
 	MessageIdsList &&items,
 	FnMut<void()> &&successCallback = nullptr);
-QPointer<Ui::BoxContent> ShowForwardMessagesBox(
+QPointer<Ui::BoxContent> ShowDropMediaBox(
 	not_null<Window::SessionNavigation*> navigation,
-	Data::ForwardDraft &&draft,
+	std::shared_ptr<QMimeData> data,
 	not_null<Data::Forum*> forum,
 	FnMut<void()> &&successCallback = nullptr);
 

Telegram/SourceFiles/window/window_session_controller.cpp

@@ -1670,26 +1670,19 @@ void SessionController::showPeerHistory(
 }
 
 void SessionController::showMessage(
-		not_null<const HistoryItem*> item) {
+		not_null<const HistoryItem*> item,
+		const SectionShow &params) {
 	_window->invokeForSessionController(
-		&item->history()->peer->session().account(),
+		&item->history()->session().account(),
 		item->history()->peer,
 		[&](not_null<SessionController*> controller) {
 			if (item->isScheduled()) {
 				controller->showSection(
 					std::make_shared<HistoryView::ScheduledMemento>(
 						item->history()),
-					SectionShow::Way::ClearStack);
-			} else if (const auto topic = item->topic()) {
-				controller->showTopic(
-					topic,
-					item->id,
-					SectionShow::Way::ClearStack);
+					params);
 			} else {
-				controller->showPeerHistory(
-					item->history()->peer,
-					SectionShow::Way::ClearStack,
-					item->id);
+				controller->content()->showMessage(item, params);
 			}
 		});
 }

Telegram/SourceFiles/window/window_session_controller.h

@@ -431,7 +431,9 @@ public:
 		const SectionShow &params = SectionShow::Way::ClearStack,
 		MsgId msgId = ShowAtUnreadMsgId) override;
 
-	void showMessage(not_null<const HistoryItem*> item);
+	void showMessage(
+		not_null<const HistoryItem*> item,
+		const SectionShow &params = SectionShow::Way::ClearStack);
 	void cancelUploadLayer(not_null<HistoryItem*> item);
 
 	void showLayer(