From e78734bbf6b2fbf1ebee530921998ff97c56f203 Mon Sep 17 00:00:00 2001
From: Aleks Kissinger <aleks0@gmail.com>
Date: Sun, 20 Sep 2020 14:20:35 +0100
Subject: [PATCH] Deserialize back to math delimiters for editing

---
 src/HtmlUtils.tsx         |  4 +++-
 src/editor/deserialize.ts | 12 ++++++++++++
 2 files changed, 15 insertions(+), 1 deletion(-)

diff --git a/src/HtmlUtils.tsx b/src/HtmlUtils.tsx
index 344fb3514c..46bc7b441c 100644
--- a/src/HtmlUtils.tsx
+++ b/src/HtmlUtils.tsx
@@ -534,7 +534,6 @@ export function checkBlockNode(node: Node) {
         case "H6":
         case "PRE":
         case "BLOCKQUOTE":
-        case "DIV":
         case "P":
         case "UL":
         case "OL":
@@ -547,6 +546,9 @@ export function checkBlockNode(node: Node) {
         case "TH":
         case "TD":
             return true;
+        case "DIV":
+            // don't treat math nodes as block nodes for deserializing
+            return !(node as HTMLElement).hasAttribute("data-mx-maths");
         default:
             return false;
     }
diff --git a/src/editor/deserialize.ts b/src/editor/deserialize.ts
index ec697b193c..edaa330e50 100644
--- a/src/editor/deserialize.ts
+++ b/src/editor/deserialize.ts
@@ -130,6 +130,18 @@ function parseElement(n: HTMLElement, partCreator: PartCreator, lastNode: HTMLEl
             }
             break;
         }
+        case "DIV":
+        case "SPAN": {
+            // math nodes are translated back into delimited latex strings
+            if (n.hasAttribute("data-mx-maths")) {
+                const delim = (n.nodeName == "SPAN") ? "$$" : "$$$";
+                const tex = n.getAttribute("data-mx-maths");
+                return partCreator.plain(delim + tex + delim);
+            } else if (!checkDescendInto(n)) {
+                return partCreator.plain(n.textContent);
+            }
+            break;
+        }
         case "OL":
             state.listIndex.push((<HTMLOListElement>n).start || 1);
             /* falls through */