Load more story users on demand.

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([&] {

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;