From 03c08ad95f7849a123784c6b63b842589855be28 Mon Sep 17 00:00:00 2001
From: 23rd <23rd@vivaldi.net>
Date: Tue, 1 Nov 2022 10:46:31 +0300
Subject: [PATCH] Added saving of scroll state in dialogs widget between chats
 filters.

---
 .../dialogs/dialogs_inner_widget.cpp          | 21 +++++++++++++++----
 .../dialogs/dialogs_inner_widget.h            |  2 ++
 2 files changed, 19 insertions(+), 4 deletions(-)

diff --git a/Telegram/SourceFiles/dialogs/dialogs_inner_widget.cpp b/Telegram/SourceFiles/dialogs/dialogs_inner_widget.cpp
index 89044d133d..2fa7135dec 100644
--- a/Telegram/SourceFiles/dialogs/dialogs_inner_widget.cpp
+++ b/Telegram/SourceFiles/dialogs/dialogs_inner_widget.cpp
@@ -2954,10 +2954,11 @@ bool InnerWidget::chooseCollapsedRow() {
 }
 
 void InnerWidget::switchToFilter(FilterId filterId) {
-	const auto found = filterId && ranges::contains(
-		session().data().chatsFilters().list(),
-		filterId,
-		&Data::ChatFilter::id);
+	const auto &list = session().data().chatsFilters().list();
+	const auto filterIt = filterId
+		? ranges::find(list, filterId, &Data::ChatFilter::id)
+		: end(list);
+	const auto found = (filterIt != end(list));
 	if (!found) {
 		filterId = 0;
 	}
@@ -2965,6 +2966,7 @@ void InnerWidget::switchToFilter(FilterId filterId) {
 		_mustScrollTo.fire({ 0, 0 });
 		return;
 	}
+	_chatsFilterScrollStates[_filterId] = -pos().y();
 	if (_openedFolder) {
 		_filterId = filterId;
 	} else {
@@ -2974,6 +2976,17 @@ void InnerWidget::switchToFilter(FilterId filterId) {
 		refreshWithCollapsedRows(true);
 	}
 	refreshEmptyLabel();
+	{
+		const auto it = _chatsFilterScrollStates.find(filterId);
+		if (it != end(_chatsFilterScrollStates)) {
+			const auto skip = found
+				// Don't save a scroll state for very flexible chat filters.
+				&& (filterIt->flags() & (Data::ChatFilter::Flag::NoRead));
+			if (!skip) {
+				_mustScrollTo.fire({ it->second, -1 });
+			}
+		}
+	}
 }
 
 bool InnerWidget::chooseHashtag() {
diff --git a/Telegram/SourceFiles/dialogs/dialogs_inner_widget.h b/Telegram/SourceFiles/dialogs/dialogs_inner_widget.h
index e97dbc0926..228c1c8c6e 100644
--- a/Telegram/SourceFiles/dialogs/dialogs_inner_widget.h
+++ b/Telegram/SourceFiles/dialogs/dialogs_inner_widget.h
@@ -443,6 +443,8 @@ private:
 		not_null<PeerData*>,
 		std::unique_ptr<Ui::VideoUserpic>> _videoUserpics;
 
+	base::flat_map<FilterId, int> _chatsFilterScrollStates;
+
 	Fn<void()> _loadMoreCallback;
 	Fn<void()> _loadMoreFilteredCallback;
 	rpl::event_stream<> _listBottomReached;