From 4a676414605bb9861908e65034b97f8d90397d9a Mon Sep 17 00:00:00 2001
From: John Preston <johnprestonmail@gmail.com>
Date: Mon, 29 May 2023 12:06:21 +0400
Subject: [PATCH] Load more story users on demand.

---
 Telegram/SourceFiles/data/data_stories.cpp         |  4 +++-
 .../SourceFiles/dialogs/dialogs_inner_widget.cpp   |  5 +++++
 .../dialogs/ui/dialogs_stories_list.cpp            | 14 ++++++++++++++
 .../SourceFiles/dialogs/ui/dialogs_stories_list.h  |  3 +++
 .../media/stories/media_stories_controller.cpp     |  5 +++++
 5 files changed, 30 insertions(+), 1 deletion(-)

diff --git a/Telegram/SourceFiles/data/data_stories.cpp b/Telegram/SourceFiles/data/data_stories.cpp
index 149125377..e86c395f3 100644
--- a/Telegram/SourceFiles/data/data_stories.cpp
+++ b/Telegram/SourceFiles/data/data_stories.cpp
@@ -299,7 +299,9 @@ void Stories::loadMore() {
 	const auto api = &_owner->session().api();
 	using Flag = MTPstories_GetAllStories::Flag;
 	_loadMoreRequestId = api->request(MTPstories_GetAllStories(
-		MTP_flags(_state.isEmpty() ? Flag(0) : Flag::f_next),
+		MTP_flags(_state.isEmpty()
+			? Flag(0)
+			: (Flag::f_next | Flag::f_state)),
 		MTP_string(_state)
 	)).done([=](const MTPstories_AllStories &result) {
 		_loadMoreRequestId = 0;
diff --git a/Telegram/SourceFiles/dialogs/dialogs_inner_widget.cpp b/Telegram/SourceFiles/dialogs/dialogs_inner_widget.cpp
index 484b840bc..1b354b377 100644
--- a/Telegram/SourceFiles/dialogs/dialogs_inner_widget.cpp
+++ b/Telegram/SourceFiles/dialogs/dialogs_inner_widget.cpp
@@ -342,6 +342,11 @@ InnerWidget::InnerWidget(
 		_controller->openPeerStories(PeerId(int64(id)));
 	}, lifetime());
 
+	_stories->loadMoreRequests(
+	) | rpl::start_with_next([=] {
+		session().data().stories().loadMore();
+	}, lifetime());
+
 	handleChatListEntryRefreshes();
 
 	refreshWithCollapsedRows(true);
diff --git a/Telegram/SourceFiles/dialogs/ui/dialogs_stories_list.cpp b/Telegram/SourceFiles/dialogs/ui/dialogs_stories_list.cpp
index 3a8cdfd0a..9e7370466 100644
--- a/Telegram/SourceFiles/dialogs/ui/dialogs_stories_list.cpp
+++ b/Telegram/SourceFiles/dialogs/ui/dialogs_stories_list.cpp
@@ -19,6 +19,7 @@ namespace {
 constexpr auto kSmallUserpicsShown = 3;
 constexpr auto kSmallReadOpacity = 0.6;
 constexpr auto kSummaryExpandLeft = 1.5;
+constexpr auto kPreloadPages = 2;
 
 [[nodiscard]] int AvailableNameWidth() {
 	const auto &full = st::dialogsStoriesFull;
@@ -206,6 +207,7 @@ void List::updateScrollMax() {
 	const auto widthFull = full.left + int(_data.items.size()) * singleFull;
 	_scrollLeftMax = std::max(widthFull - width(), 0);
 	_scrollLeft = std::clamp(_scrollLeft, 0, _scrollLeftMax);
+	checkLoadMore();
 	update();
 }
 
@@ -221,6 +223,10 @@ rpl::producer<> List::entered() const {
 	return _entered.events();
 }
 
+rpl::producer<> List::loadMoreRequests() const {
+	return _loadMoreRequests.events();
+}
+
 void List::enterEventHook(QEnterEvent *e) {
 	_entered.fire({});
 }
@@ -597,6 +603,7 @@ void List::wheelEvent(QWheelEvent *e) {
 		_expandRequests.fire({});
 		_scrollLeft = next;
 		updateSelected();
+		checkLoadMore();
 		update();
 	}
 	e->accept();
@@ -640,11 +647,18 @@ void List::checkDragging() {
 			_scrollLeftMax);
 		if (newLeft != _scrollLeft) {
 			_scrollLeft = newLeft;
+			checkLoadMore();
 			update();
 		}
 	}
 }
 
+void List::checkLoadMore() {
+	if (_scrollLeftMax - _scrollLeft < width() * kPreloadPages) {
+		_loadMoreRequests.fire({});
+	}
+}
+
 void List::mouseReleaseEvent(QMouseEvent *e) {
 	_lastMousePosition = e->globalPos();
 	const auto guard = gsl::finally([&] {
diff --git a/Telegram/SourceFiles/dialogs/ui/dialogs_stories_list.h b/Telegram/SourceFiles/dialogs/ui/dialogs_stories_list.h
index 1286db93e..06a0fc286 100644
--- a/Telegram/SourceFiles/dialogs/ui/dialogs_stories_list.h
+++ b/Telegram/SourceFiles/dialogs/ui/dialogs_stories_list.h
@@ -47,6 +47,7 @@ public:
 	[[nodiscard]] rpl::producer<uint64> clicks() const;
 	[[nodiscard]] rpl::producer<> expandRequests() const;
 	[[nodiscard]] rpl::producer<> entered() const;
+	[[nodiscard]] rpl::producer<> loadMoreRequests() const;
 
 private:
 	struct Layout;
@@ -110,6 +111,7 @@ private:
 	void updateSelected();
 	void checkDragging();
 	bool finishDragging();
+	void checkLoadMore();
 
 	void updateHeight();
 	void toggleAnimated(bool shown);
@@ -128,6 +130,7 @@ private:
 	rpl::event_stream<uint64> _clicks;
 	rpl::event_stream<> _expandRequests;
 	rpl::event_stream<> _entered;
+	rpl::event_stream<> _loadMoreRequests;
 
 	Ui::Animations::Simple _shownAnimation;
 
diff --git a/Telegram/SourceFiles/media/stories/media_stories_controller.cpp b/Telegram/SourceFiles/media/stories/media_stories_controller.cpp
index 0edb1baec..c0eb8153a 100644
--- a/Telegram/SourceFiles/media/stories/media_stories_controller.cpp
+++ b/Telegram/SourceFiles/media/stories/media_stories_controller.cpp
@@ -40,6 +40,7 @@ constexpr auto kSiblingMultiplierMax = 0.72;
 constexpr auto kSiblingOutsidePart = 0.24;
 constexpr auto kSiblingUserpicSize = 0.3;
 constexpr auto kInnerHeightMultiplier = 1.6;
+constexpr auto kPreloadUsersCount = 3;
 
 } // namespace
 
@@ -381,6 +382,10 @@ void Controller::show(
 	}
 	_index = subindex;
 
+	if (int(lists.size()) - index < kPreloadUsersCount) {
+		story->peer()->owner().stories().loadMore();
+	}
+
 	const auto storyId = FullStoryId{
 		.peer = list.user->id,
 		.story = id,