Fix long message parts highlighting in topics.

Telegram/SourceFiles/history/history_widget.cpp

@@ -1433,41 +1433,12 @@ int HistoryWidget::itemTopForHighlight(
 	const auto heightLeft = (visibleAreaHeight - viewHeight);
 	if (heightLeft >= 0) {
 		return std::max(itemTop - (heightLeft / 2), 0);
-	} else if (const auto sel = itemHighlight(item).range; !sel.empty()) {
+	} else if (const auto sel = itemHighlight(item).range
-		auto request = HistoryView::StateRequest();
+		; !sel.empty() && !IsSubGroupSelection(sel)) {
-		request.flags = Ui::Text::StateRequest::Flag::LookupSymbol;
 		const auto single = st::messageTextStyle.font->height;
-		const auto findy = [&](int symbol, int yfrom = 0) {
+		const auto begin = HistoryView::FindViewY(view, sel.from) - single;
-			const auto fory = [&](int y) {
+		const auto end = HistoryView::FindViewY(view, sel.to, begin + single)
-				return view->textState(QPoint(0, y), request).symbol;
+			+ 2 * single;
-			};
-			auto ytill = view->height() - 1;
-			auto symbolfrom = fory(yfrom);
-			auto symboltill = fory(ytill);
-			if ((yfrom >= ytill) || (symbolfrom >= symbol)) {
-				return yfrom;
-			} else if (symboltill <= symbol) {
-				return ytill;
-			}
-			while (ytill - yfrom >= 2 * single) {
-				const auto middle = (yfrom + ytill) / 2;
-				const auto found = fory(middle);
-				if (found == symbol
-					|| symbolfrom > found
-					|| symboltill < found) {
-					return middle;
-				} else if (found < symbol) {
-					yfrom = middle;
-					symbolfrom = found;
-				} else {
-					ytill = middle;
-					symboltill = found;
-				}
-			}
-			return (yfrom + ytill) / 2;
-		};
-		const auto begin = findy(sel.from) - single;
-		const auto end = findy(sel.to, begin + single) + 2 * single;
 		auto result = itemTop;
 		if (end > visibleAreaHeight) {
 			result = std::max(result, itemTop + end - visibleAreaHeight);

Telegram/SourceFiles/history/view/history_view_element.cpp

@@ -2015,4 +2015,37 @@ void Element::ClearGlobal() {
 	MousedElement = nullptr;
 }
 
+int FindViewY(not_null<Element*> view, uint16 symbol, int yfrom) {
+	auto request = HistoryView::StateRequest();
+	request.flags = Ui::Text::StateRequest::Flag::LookupSymbol;
+	const auto single = st::messageTextStyle.font->height;
+	const auto fory = [&](int y) {
+		return view->textState(QPoint(0, y), request).symbol;
+	};
+	auto ytill = view->height() - 1;
+	auto symbolfrom = fory(yfrom);
+	auto symboltill = fory(ytill);
+	if ((yfrom >= ytill) || (symbolfrom >= symbol)) {
+		return yfrom;
+	} else if (symboltill <= symbol) {
+		return ytill;
+	}
+	while (ytill - yfrom >= 2 * single) {
+		const auto middle = (yfrom + ytill) / 2;
+		const auto found = fory(middle);
+		if (found == symbol
+			|| symbolfrom > found
+			|| symboltill < found) {
+			return middle;
+		} else if (found < symbol) {
+			yfrom = middle;
+			symbolfrom = found;
+		} else {
+			ytill = middle;
+			symboltill = found;
+		}
+	}
+	return (yfrom + ytill) / 2;
+}
+
 } // namespace HistoryView

Telegram/SourceFiles/history/view/history_view_element.h

@@ -668,4 +668,9 @@ private:
 
 };
 
+[[nodiscard]] int FindViewY(
+	not_null<Element*> view,
+	uint16 symbol,
+	int yfrom = 0);
+
 } // namespace HistoryView

Telegram/SourceFiles/history/view/history_view_list_widget.cpp

@@ -711,7 +711,25 @@ std::optional<int> ListWidget::scrollTopForView(
 	const auto top = view->y();
 	const auto height = view->height();
 	const auto available = _visibleBottom - _visibleTop;
-	return top - std::max((available - height) / 2, 0);
+	const auto heightLeft = (available - height);
+	if (heightLeft >= 0) {
+		return std::max(top - (heightLeft / 2), 0);
+	} else if (const auto sel = _highlighter.state(view->data()).range
+		; !sel.empty() && !IsSubGroupSelection(sel)) {
+		const auto single = st::messageTextStyle.font->height;
+		const auto begin = HistoryView::FindViewY(view, sel.from) - single;
+		const auto end = HistoryView::FindViewY(view, sel.to, begin + single)
+			+ 2 * single;
+		auto result = top;
+		if (end > available) {
+			result = std::max(result, top + end - available);
+		}
+		if (top + begin < result) {
+			result = top + begin;
+		}
+		return result;
+	}
+	return top;
 }
 
 void ListWidget::scrollTo(
@@ -873,24 +891,31 @@ bool ListWidget::showAtPositionNow(
 		Data::MessagePosition position,
 		const Window::SectionShow &params,
 		Fn<void(bool found)> done) {
-	if (const auto scrollTop = scrollTopForPosition(position)) {
+	auto scrollTop = scrollTopForPosition(position);
-		computeScrollTo(*scrollTop, position, params.animated);
+	if (!scrollTop.has_value()) {
-		if (position != Data::MaxMessagePosition
+		return false;
-			&& position != Data::UnreadMessagePosition) {
-			highlightMessage(
-				position.fullId,
-				params.highlightPart,
-				params.highlightPartOffsetHint);
-		}
-		if (done) {
-			const auto found = !position.fullId.peer
-				|| !IsServerMsgId(position.fullId.msg)
-				|| viewForItem(position.fullId);
-			done(found);
-		}
-		return true;
 	}
-	return false;
+	if (position != Data::MaxMessagePosition
+		&& position != Data::UnreadMessagePosition) {
+		const auto hasHighlight = !params.highlightPart.empty();
+		highlightMessage(
+			position.fullId,
+			params.highlightPart,
+			params.highlightPartOffsetHint);
+		if (hasHighlight) {
+			// We may want to scroll to a different part of the message.
+			scrollTop = scrollTopForPosition(position);
+			Assert(scrollTop.has_value());
+		}
+	}
+	computeScrollTo(*scrollTop, position, params.animated);
+	if (done) {
+		const auto found = !position.fullId.peer
+			|| !IsServerMsgId(position.fullId.msg)
+			|| viewForItem(position.fullId);
+		done(found);
+	}
+	return true;
 }
 
 void ListWidget::computeScrollTo(