Auto-detected rtl flag for composed rich messages.

Telegram/SourceFiles/iv/editor/iv_editor_state.cpp

@@ -8905,6 +8905,7 @@ void State::rebuild() {
 
 void State::rebuildPrepared() {
 	_lastPreparedMutationKind = PreparedMutationKind::FullRebuild;
+	_richPage->rtl = DetermineRichPageRtl(*_richPage);
 	_prepared = Markdown::TryPrepareNativeInstantView({
 		.richPage = _richPage,
 		.mediaRuntime = _mediaRuntime,

Telegram/SourceFiles/iv/iv_rich_message_serializer.cpp

@@ -1736,7 +1736,7 @@ SerializeInputRichMessageResult SerializeInputRichMessage(
 	}
 	using Flag = MTPDinputRichMessage::Flag;
 	auto flags = MTPDinputRichMessage::Flags();
-	if (page.rtl) {
+	if (DetermineRichPageRtl(page)) {
 		flags |= Flag::f_rtl;
 	}
 	if (!photos.isEmpty()) {

Telegram/SourceFiles/iv/iv_rich_page.cpp

@@ -2252,6 +2252,35 @@ std::shared_ptr<const RichPage> ParsePage(
 	return true;
 }
 
+[[nodiscard]] std::optional<bool> RichTextRtl(const RichText &text) {
+	const auto &plain = text.text.text;
+	if (plain.trimmed().isEmpty()) {
+		return std::nullopt;
+	}
+	return plain.isRightToLeft();
+}
+
+[[nodiscard]] std::optional<bool> BlocksTextRtl(
+		const std::vector<Block> &blocks) {
+	for (const auto &block : blocks) {
+		if (const auto result = RichTextRtl(block.text)) {
+			return result;
+		}
+		if (const auto result = BlocksTextRtl(block.blocks)) {
+			return result;
+		}
+		for (const auto &item : block.listItems) {
+			if (const auto result = RichTextRtl(item.text)) {
+				return result;
+			}
+			if (const auto result = BlocksTextRtl(item.blocks)) {
+				return result;
+			}
+		}
+	}
+	return std::nullopt;
+}
+
 } // namespace
 
 bool RichPagesEqual(
@@ -2443,6 +2472,10 @@ TextWithEntities FlattenRichPageToSimpleText(const RichPage &page) {
 	return result;
 }
 
+bool DetermineRichPageRtl(const RichPage &page) {
+	return BlocksTextRtl(page.blocks).value_or(false);
+}
+
 std::optional<TextWithEntities> SerializeAsSimple(
 		const RichPage &page,
 		not_null<Main::Session*> session) {

Telegram/SourceFiles/iv/iv_rich_page.h

@@ -312,5 +312,6 @@ inline constexpr auto kTextDiffDeletedColorIndex = 11;
 	bool emptyFallback = true);
 [[nodiscard]] TextWithEntities FlattenRichPageToSimpleText(
 	const RichPage &page);
+[[nodiscard]] bool DetermineRichPageRtl(const RichPage &page);
 
 } // namespace Iv