issue doxygen#11828 Inconsistent vertical spacing of ordered list items in generated HTML

The current situation is a bit inconsistent as depending on the number of paragraphs in an item the `<p class="startli">` is added or nor.

In case one of the items consists of multiple paragraphs the `<p class="startli">` is added for all paragraphs in the items in the current item block.
When having maximal 1 paragraph for each item the  `<p class="startlisingle">` is added so the user can (through a css file) choose a different layout for both situations.

Author: albert-github

src/docnode.cpp

@@ -3017,6 +3017,7 @@ Token DocAutoList::parse()
 
     children().append<DocAutoListItem>(parser(),thisVariant(),m_indent,num++);
     retval = children().get_last<DocAutoListItem>()->parse();
+    m_singleParagraph = m_singleParagraph &&  children().get_last<DocAutoListItem>()->children().size()<=1 ;
     //printf("DocAutoList::parse(): retval=0x%x parser()->context.token->indent=%d m_indent=%d "
     //       "m_isEnumList=%d parser()->context.token->isEnumList=%d parser()->context.token->name=%s\n",
     //       retval,parser()->context.token->indent,m_indent,m_isEnumList,parser()->context.token->isEnumList,
@@ -3031,6 +3032,7 @@ Token DocAutoList::parse()
         );
 
   parser()->tokenizer.endAutoList();
+
   AUTO_TRACE_EXIT("retval={}",retval.to_string());
   return retval;
 }

src/docnode.h

@@ -580,13 +580,15 @@ class DocAutoList : public DocCompoundNode
     bool isEnumList() const    { return m_isEnumList; }
     int  indent() const        { return m_indent; }
     bool isCheckedList() const { return m_isCheckedList; }
+    bool isSingleParagraph() const { return m_singleParagraph; }
     int depth() const          { return m_depth; }
     Token parse();
 
   private:
     int      m_indent = 0;
     bool     m_isEnumList = false;
     bool     m_isCheckedList = false;
+    bool     m_singleParagraph = true;
     int      m_depth = 0;
 };
 

src/htmldocvisitor.cpp

@@ -53,7 +53,8 @@ enum class contexts_t
     ENDTD,     // 6
     INTERLI,   // 7
     INTERDD,   // 8
-    INTERTD    // 9
+    INTERTD,   // 9
+    STARTLISINGLE   // 10
 };
 
 static constexpr const char *contexts(contexts_t type)
@@ -62,6 +63,7 @@ static constexpr const char *contexts(contexts_t type)
   {
     case contexts_t::NONE:    return nullptr;
     case contexts_t::STARTLI: return "startli";
+    case contexts_t::STARTLISINGLE: return "startlisingle";
     case contexts_t::STARTDD: return "startdd";
     case contexts_t::ENDLI:   return "endli";
     case contexts_t::ENDDD:   return "enddd";
@@ -1171,7 +1173,14 @@ static contexts_t getParagraphContext(const DocPara &p,bool &isFirst,bool &isLas
     {
       isFirst=isFirstChildNode(docAutoListItem,p);
       isLast =isLastChildNode (docAutoListItem,p);
-      t=contexts_t::STARTLI; // not used
+      if (std::get_if<DocAutoList>(docAutoListItem->parent())->isSingleParagraph())
+      {
+        t=contexts_t::STARTLISINGLE; // not used
+      }
+      else
+      {
+        t=contexts_t::STARTLI; // not used
+      }
       return t;
     }
     const auto docSimpleListItem = std::get_if<DocSimpleListItem>(p.parent());
@@ -1327,7 +1336,7 @@ void HtmlDocVisitor::operator()(const DocPara &p)
   bool isLast  = false;
   contexts_t t = getParagraphContext(p,isFirst,isLast);
   //printf("startPara first=%d last=%d\n",isFirst,isLast);
-  if (isFirst && isLast) needsTagBefore=FALSE;
+  if (!std::holds_alternative<DocAutoListItem>(*p.parent()) && isFirst && isLast) needsTagBefore=FALSE;
 
   //printf("  needsTagBefore=%d\n",needsTagBefore);
   // write the paragraph tag (if needed)
@@ -1372,7 +1381,7 @@ void HtmlDocVisitor::operator()(const DocPara &p)
   }
 
   //printf("endPara first=%d last=%d\n",isFirst,isLast);
-  if (isFirst && isLast) needsTagAfter=FALSE;
+  if (!std::holds_alternative<DocAutoListItem>(*p.parent()) && isFirst && isLast) needsTagAfter=FALSE;
 
   //printf("  needsTagAfter=%d\n",needsTagAfter);
   if (needsTagAfter) m_t << "</p>\n";
@@ -2368,7 +2377,7 @@ void HtmlDocVisitor::forceEndParagraph(const Node &n)
     bool isLast = false;
     getParagraphContext(*para,isFirst,isLast);
     //printf("forceEnd first=%d last=%d styleOutsideParagraph=%d\n",isFirst,isLast,styleOutsideParagraph);
-    if (isFirst && isLast) return;
+    if (!std::holds_alternative<DocAutoListItem>(*para->parent()) && isFirst && isLast) return;
     if (styleOutsideParagraph) return;
 
     //printf("adding </p>\n");
@@ -2417,7 +2426,7 @@ void HtmlDocVisitor::forceStartParagraph(const Node &n)
     bool isFirst = false;
     bool isLast = false;
     getParagraphContext(*para,isFirst,isLast);
-    if (isFirst && isLast) needsTag = false;
+    if (!std::holds_alternative<DocAutoListItem>(*para->parent()) && isFirst && isLast)  needsTag = false;
     //printf("forceStart first=%d last=%d needsTag=%d\n",isFirst,isLast,needsTag);
 
     if (needsTag) m_t << "<p>";

templates/html/doxygen.css

@@ -79,6 +79,11 @@ p.startli, p.startdd {
 	margin-top: 2px;
 }
 
+p.startlisingle {
+	margin-top: 0px;
+	margin-bottom: 0px;
+}
+
 th p.starttd, th p.intertd, th p.endtd {
 	font-size: 100%;
 	font-weight: 700;