Allow animated scroll-to in BoxContent.

ui/layers/box_content.cpp

@@ -263,8 +263,21 @@ RectParts BoxContent::customCornersFilling() {
 }
 
 void BoxContent::scrollToY(int top, int bottom) {
+	scrollTo({ top, bottom });
+}
+
+void BoxContent::scrollTo(ScrollToRequest request, anim::type animated) {
 	if (_scroll) {
-		_scroll->scrollToY(top, bottom);
+		const auto v = _scroll->computeScrollTo(request.ymin, request.ymax);
+		const auto now = _scroll->scrollTop();
+		if (animated == anim::type::instant || v == now) {
+			_scrollAnimation.stop();
+			_scroll->scrollToY(v);
+		} else {
+			_scrollAnimation.start([=] {
+				_scroll->scrollToY(_scrollAnimation.value(v));
+			}, now, v, st::slideWrapDuration, anim::sineInOut);
+		}
 	}
 }
 

ui/layers/box_content.h

@@ -13,6 +13,7 @@
 #include "ui/widgets/labels.h"
 #include "ui/layers/layer_widget.h"
 #include "ui/layers/show.h"
+#include "ui/effects/animations.h"
 #include "ui/effects/animation_value.h"
 #include "ui/text/text_entity.h"
 #include "ui/rp_widget.h"
@@ -59,6 +60,7 @@ class ScrollArea;
 class FlatLabel;
 class FadeShadow;
 class BoxContent;
+struct ScrollToRequest;
 
 class BoxContentDelegate {
 public:
@@ -213,6 +215,9 @@ public:
 	void scrollByDraggingDelta(int delta);
 
 	void scrollToY(int top, int bottom = -1);
+	void scrollTo(
+		ScrollToRequest request,
+		anim::type animated = anim::type::instant);
 	void sendScrollViewportEvent(not_null<QEvent*> event);
 	[[nodiscard]] rpl::producer<> scrolls() const;
 	[[nodiscard]] int scrollTop() const;
@@ -309,6 +314,7 @@ private:
 	object_ptr<FadeShadow> _bottomShadow = { nullptr };
 
 	Ui::DraggingScrollManager _draggingScroll;
+	Ui::Animations::Simple _scrollAnimation;
 
 	rpl::event_stream<> _boxClosingStream;
 

ui/widgets/scroll_area.cpp

@@ -706,32 +706,48 @@ void ScrollArea::scrollToWidget(not_null<QWidget*> widget) {
 	}
 }
 
-void ScrollArea::scrollToY(int toTop, int toBottom) {
+int ScrollArea::computeScrollTo(int toTop, int toBottom) {
 	if (const auto inner = widget()) {
 		SendPendingMoveResizeEvents(inner);
 	}
 	SendPendingMoveResizeEvents(this);
 
-	int toMin = 0, toMax = scrollTopMax();
+	const auto toMin = 0;
+	const auto toMax = scrollTopMax();
 	if (toTop < toMin) {
 		toTop = toMin;
 	} else if (toTop > toMax) {
 		toTop = toMax;
 	}
-	bool exact = (toBottom < 0);
+	const auto exact = (toBottom < 0);
 
-	int curTop = scrollTop(), curHeight = height(), curBottom = curTop + curHeight, scToTop = toTop;
+	const auto curTop = scrollTop();
+	const auto curHeight = height();
+	const auto curBottom = curTop + curHeight;
+	auto scToTop = toTop;
 	if (!exact && toTop >= curTop) {
-		if (toBottom < toTop) toBottom = toTop;
-		if (toBottom <= curBottom) return;
+		if (toBottom < toTop) {
+			toBottom = toTop;
+		}
+		if (toBottom <= curBottom) {
+			return curTop;
+		}
 
 		scToTop = toBottom - curHeight;
-		if (scToTop > toTop) scToTop = toTop;
-		if (scToTop == curTop) return;
+		if (scToTop > toTop) {
+			scToTop = toTop;
+		}
+		if (scToTop == curTop) {
+			return curTop;
+		}
 	} else {
 		scToTop = toTop;
 	}
-	verticalScrollBar()->setValue(scToTop);
+	return scToTop;
+}
+
+void ScrollArea::scrollToY(int toTop, int toBottom) {
+	verticalScrollBar()->setValue(computeScrollTo(toTop, toBottom));
 }
 
 void ScrollArea::doSetOwnedWidget(object_ptr<QWidget> w) {

ui/widgets/scroll_area.h

@@ -166,6 +166,7 @@ public:
 
 	void scrollTo(ScrollToRequest request);
 	void scrollToWidget(not_null<QWidget*> widget);
+	[[nodiscard]] int computeScrollTo(int toTop, int toBottom);
 
 	void scrollToY(int toTop, int toBottom = -1);
 	void disableScroll(bool dis);