From 21dfb310f334aaad84a9c41fbc6dd426831b41be Mon Sep 17 00:00:00 2001
From: John Preston <johnprestonmail@gmail.com>
Date: Tue, 25 Jun 2019 14:59:22 +0200
Subject: [PATCH] Optimize animated sticker preview.

---
 Telegram/SourceFiles/window/layer_widget.cpp | 15 +++++++++++++--
 Telegram/SourceFiles/window/layer_widget.h   |  1 +
 2 files changed, 14 insertions(+), 2 deletions(-)

diff --git a/Telegram/SourceFiles/window/layer_widget.cpp b/Telegram/SourceFiles/window/layer_widget.cpp
index 894a4b559..bd86a882e 100644
--- a/Telegram/SourceFiles/window/layer_widget.cpp
+++ b/Telegram/SourceFiles/window/layer_widget.cpp
@@ -864,6 +864,13 @@ MediaPreviewWidget::MediaPreviewWidget(
 	subscribe(Auth().downloaderTaskFinished(), [this] { update(); });
 }
 
+QRect MediaPreviewWidget::updateArea() const {
+	const auto size = currentDimensions();
+	return QRect(
+		QPoint((width() - size.width()) / 2, (height() - size.height()) / 2),
+		size);
+}
+
 void MediaPreviewWidget::paintEvent(QPaintEvent *e) {
 	Painter p(this);
 	QRect r(e->rect());
@@ -1048,7 +1055,11 @@ void MediaPreviewWidget::setupLottie() {
 
 	_lottie->updates(
 	) | rpl::start_with_next_error([=](Lottie::Update update) {
-		this->update();
+		update.data.match([&](const Lottie::Information &) {
+			this->update();
+		}, [&](const Lottie::DisplayFrameRequest &) {
+			this->update(updateArea());
+		});
 	}, [=](Lottie::Error error) {
 	}, lifetime());
 }
@@ -1152,7 +1163,7 @@ void MediaPreviewWidget::clipCallback(Media::Clip::Notification notification) {
 
 	case NotificationRepaint: {
 		if (_gif && !_gif->currentDisplayed()) {
-			update();
+			updateArea();
 		}
 	} break;
 	}
diff --git a/Telegram/SourceFiles/window/layer_widget.h b/Telegram/SourceFiles/window/layer_widget.h
index 762119760..c19567516 100644
--- a/Telegram/SourceFiles/window/layer_widget.h
+++ b/Telegram/SourceFiles/window/layer_widget.h
@@ -226,6 +226,7 @@ private:
 	void startShow();
 	void fillEmojiString();
 	void resetGifAndCache();
+	QRect updateArea() const;
 
 	not_null<Window::SessionController*> _controller;