Generate a nested nav if parts exist and the nested flag is on

novelwriter/formats/toepub.py

@@ -103,10 +103,7 @@ class ToEPub(ToHtml):
     ##
 
     def setReplaceUnicode(self, doReplace: bool) -> None:
-        """Set translation map.
-
-        Replace Unicode is ignored for EPub.
-        """
+        """Set translation map. Replace Unicode is ignored for EPub."""
         self._trMap = str.maketrans({"&": "&"})
 
     ##
@@ -382,15 +379,42 @@ class ToEPub(ToHtml):
         xHtml.append("</header>")
         xHtml.append('<nav epub:type="toc" role="doc-toc" aria-labelledby="toc">')
         xHtml.append('<ol epub:type="list">')
-        xHtml.extend(
-            f'<li><a href="xhtml/{section.name}.xhtml#{section.sectionID}">{title}</a></li>'
-            for section in self._sections
-            if (title := section.title) and section.epubType != EPubType.COVER
-        )
+
+        nested = self._nestedToc and any(s.epubType == EPubType.PART for s in self._sections)
+        inPart = False
+        inList = False
+        for section in self._sections:
+            if not (title := section.title) or section.epubType == EPubType.COVER:
+                continue
+            link = f'<a href="xhtml/{section.name}.xhtml#{section.sectionID}">{title}</a>'
+            if inPart and section.epubType == EPubType.CHAPTER:
+                if not inList:
+                    # A nested list must not be empty, so open it on first child
+                    xHtml.append("<ol>")
+                    inList = True
+                xHtml.append(f"<li>{link}</li>")
+                continue
+            if inList:
+                xHtml.append("</ol>")
+                inList = False
+            if inPart:
+                xHtml.append("</li>")
+                inPart = False
+            if nested and section.epubType == EPubType.PART:
+                xHtml.append(f"<li>{link}")
+                inPart = True
+            else:
+                xHtml.append(f"<li>{link}</li>")
+        if inList:
+            xHtml.append("</ol>")
+        if inPart:
+            xHtml.append("</li>")
+
         xHtml.append("</ol>")
         xHtml.append("</nav>")
         xHtml.append("</body>")
         xHtml.append("</html>")
+
         return "\n".join(xHtml)
 
     def _generateStyleSheet(self) -> str:

novelwriter/formats/tohtml.py

@@ -81,12 +81,13 @@ class ToHtml(Tokenizer):
     Extend the Tokenizer class to write HTML output.
     """
 
-    __slots__ = ("_brTag", "_cssStyles", "_trMap", "_usedFields", "_usedNotes")
+    __slots__ = ("_brTag", "_cssStyles", "_nestedToc", "_trMap", "_usedFields", "_usedNotes")
 
     def __init__(self, project: NWProject) -> None:
         super().__init__(project)
         self._trMap = {}
         self._cssStyles = True
+        self._nestedToc = False
         self._usedNotes: dict[str, int] = {}
         self._usedFields: list[tuple[int, str]] = []
         self._brTag = "<br>"
@@ -114,6 +115,10 @@ class ToHtml(Tokenizer):
             # Extend to all relevant Unicode characters
             self._trMap.update(str.maketrans(nwHtmlUnicode.U_TO_H))
 
+    def setNestedToC(self, value: bool) -> None:
+        """Set a nested table of contents."""
+        self._nestedToc = value
+
     ##
     #  Class Methods
     ##

novelwriter/manuscript/docbuild.py

@@ -348,6 +348,9 @@ class DocumentBuilder:
         bldObj.setCommentType(nwComment.STORY, self._build.getBool("text.includeStory"))
         bldObj.setCommentType(nwComment.NOTE, self._build.getBool("text.includeNotes"))
 
+        if isinstance(bldObj, ToEPub):
+            bldObj.setNestedToC(self._build.getBool("epub.nestedToc"))
+
         if isinstance(bldObj, ToHtml):
             bldObj.setStyles(self._build.getBool("html.addStyles"))
             bldObj.setReplaceUnicode(self._build.getBool("format.stripUnicode"))