Target collage spoiler at the clicked media item

Telegram/SourceFiles/iv/iv_cached_media.cpp

@@ -1462,7 +1462,10 @@ auto CachedPageMediaRuntime::hostedMediaBlockFactory() const
 			const auto medias = std::make_shared<
 				std::vector<std::unique_ptr<::Data::Media>>>();
 			medias->reserve(prepared.items.size());
-			for (const auto &item : prepared.items) {
+			for (auto i = 0, count = int(prepared.items.size())
+					; i != count
+					; ++i) {
+				const auto &item = prepared.items[i];
 				const auto kind = item.media.kind;
 				if (kind == Markdown::PreparedMediaItemKind::Photo) {
 					const auto photo = session->data().photo(
@@ -1482,6 +1485,7 @@ auto CachedPageMediaRuntime::hostedMediaBlockFactory() const
 							photo,
 							origin,
 							host->item()->fullId()));
+					descriptor.groupedItemIndices.emplace(photo->id, i);
 				} else {
 					const auto document = session->data().document(
 						DocumentId(item.media.id));
@@ -1504,6 +1508,7 @@ auto CachedPageMediaRuntime::hostedMediaBlockFactory() const
 							document,
 							origin,
 							host->item()->fullId()));
+					descriptor.groupedItemIndices.emplace(document->id, i);
 				}
 				if (!medias->back()->canBeGrouped()) {
 					return std::shared_ptr<Markdown::MediaBlock>();

Telegram/SourceFiles/iv/markdown/iv_markdown_history_view_media.cpp

@@ -227,6 +227,7 @@ private:
 	const base::flat_map<
 		uint64,
 		std::shared_ptr<DocumentRuntime>> _groupedDocumentRuntimes;
+	const base::flat_map<uint64, int> _groupedItemIndices;
 	const std::shared_ptr<IvHistoryViewMediaHost> _host;
 	const std::vector<std::shared_ptr<void>> _keepAlive;
 	std::unique_ptr<HistoryView::Media> _media;
@@ -246,6 +247,7 @@ IvHistoryViewBlock::IvHistoryViewBlock(
 , _documentRuntime(std::move(descriptor.document))
 , _groupedPhotoRuntimes(std::move(descriptor.groupedPhotos))
 , _groupedDocumentRuntimes(std::move(descriptor.groupedDocuments))
+, _groupedItemIndices(std::move(descriptor.groupedItemIndices))
 , _host(std::move(descriptor.host))
 , _keepAlive(std::move(descriptor.keepAlive)) {
 	if (descriptor.mediaFactory) {
@@ -427,6 +429,11 @@ IvHistoryViewHit IvHistoryViewBlock::classifyHandler(
 			if (i != end(_groupedPhotoRuntimes)) {
 				result.activation.kind = MediaActivationKind::Photo;
 				result.activation.photo = i->second;
+				const auto j = _groupedItemIndices.find(
+					photoOpen->photo()->id);
+				if (j != end(_groupedItemIndices)) {
+					result.activation.itemIndex = j->second;
+				}
 				return result;
 			}
 		} else if (const auto documentOpen
@@ -436,6 +443,11 @@ IvHistoryViewHit IvHistoryViewBlock::classifyHandler(
 			if (i != end(_groupedDocumentRuntimes)) {
 				result.activation.kind = MediaActivationKind::Document;
 				result.activation.document = i->second;
+				const auto j = _groupedItemIndices.find(
+					documentOpen->document()->id);
+				if (j != end(_groupedItemIndices)) {
+					result.activation.itemIndex = j->second;
+				}
 				return result;
 			}
 		}

Telegram/SourceFiles/iv/markdown/iv_markdown_history_view_media.h

@@ -92,6 +92,7 @@ struct IvHistoryViewMediaDescriptor {
 	base::flat_map<
 		uint64,
 		std::shared_ptr<DocumentRuntime>> groupedDocuments;
+	base::flat_map<uint64, int> groupedItemIndices;
 };
 
 class IvHistoryViewMediaBlockFactory final : public HostedMediaBlockFactory {