diff --git a/src/public/app/widgets/type_widgets/ckeditor/syntax_highlight.js b/src/public/app/widgets/type_widgets/ckeditor/syntax_highlight.js
index f3dcbc584..abf0ca1a5 100644
--- a/src/public/app/widgets/type_widgets/ckeditor/syntax_highlight.js
+++ b/src/public/app/widgets/type_widgets/ckeditor/syntax_highlight.js
@@ -1,3 +1,131 @@
-export function initSyntaxHighlighting() {
+export function initSyntaxHighlighting(editor) {
     console.log("Init syntax highlight");
+    initTextEditor(editor);
+}
+
+const tag = "SyntaxHighlightWidget";
+const debugLevels = ["error", "warn", "info", "log", "debug"];
+const debugLevel = "debug";
+
+let warn = function() {};
+if (debugLevel >= debugLevels.indexOf("warn")) {
+    warn = console.warn.bind(console, tag + ": ");
+}
+
+let info = function() {};
+if (debugLevel >= debugLevels.indexOf("info")) {
+    info = console.info.bind(console, tag + ": ");
+}
+
+let log = function() {};
+if (debugLevel >= debugLevels.indexOf("log")) {
+    log = console.log.bind(console, tag + ": ");
+}
+
+let dbg = function() {};
+if (debugLevel >= debugLevels.indexOf("debug")) {
+    dbg = console.debug.bind(console, tag + ": ");
+}
+
+function assert(e, msg) {
+    console.assert(e, tag + ": " + msg);
+}
+
+function initTextEditor(textEditor) {
+    log("initTextEditor");
+
+    let widget = this;
+    const document = textEditor.model.document;
+
+    // Create a conversion from model to view that converts 
+    // hljs:hljsClassName:uniqueId into a span with hljsClassName
+    // See the list of hljs class names at
+    // https://github.com/highlightjs/highlight.js/blob/6b8c831f00c4e87ecd2189ebbd0bb3bbdde66c02/docs/css-classes-reference.rst
+
+    textEditor.conversion.for('editingDowncast').markerToHighlight( {
+        model: "hljs",
+        view: ( { markerName } ) => {
+            dbg("markerName " + markerName);
+            // markerName has the pattern addMarker:cssClassName:uniqueId
+            const [ , cssClassName, id ] = markerName.split( ':' );
+
+            // The original code at 
+            // https://github.com/ckeditor/ckeditor5/blob/master/packages/ckeditor5-find-and-replace/src/findandreplaceediting.js
+            // has this comment
+            //      Marker removal from the view has a bug: 
+            //      https://github.com/ckeditor/ckeditor5/issues/7499
+            //      A minimal option is to return a new object for each converted marker...
+            return {
+                name: 'span',
+                classes: [ cssClassName ],
+                attributes: {
+                    // ...however, adding a unique attribute should be future-proof..
+                    'data-syntax-result': id
+                },
+            };
+        }
+    });
+    
+
+    // XXX This is done at BalloonEditor.create time, so it assumes this
+    //     document is always attached to this textEditor, empirically that
+    //     seems to be the case even with two splits showing the same note,
+    //     it's not clear if CKEditor5 has apis to attach and detach
+    //     documents around
+    document.registerPostFixer(function(writer) {
+        log("postFixer");
+        // Postfixers are a simpler way of tracking changes than onchange
+        // See
+        // https://github.com/ckeditor/ckeditor5/blob/b53d2a4b49679b072f4ae781ac094e7e831cfb14/packages/ckeditor5-block-quote/src/blockquoteediting.js#L54
+        const changes = document.differ.getChanges();
+        let dirtyCodeBlocks = new Set();
+
+        for (const change of changes) {
+            dbg("change " + JSON.stringify(change));
+
+            if ((change.type == "insert") && (change.name == "codeBlock")) {
+                // A new code block was inserted
+                const codeBlock = change.position.nodeAfter;
+                // Even if it's a new codeblock, it needs dirtying in case
+                // it already has children, like when pasting one or more
+                // full codeblocks, undoing a delete, changing the language,
+                // etc (the postfixer won't get later changes for those).
+                log("dirtying inserted codeBlock " + JSON.stringify(codeBlock.toJSON()));
+                dirtyCodeBlocks.add(codeBlock);
+                
+            } else if (change.type == "remove" && (change.name == "codeBlock")) {
+                // An existing codeblock was removed, do nothing. Note the
+                // node is no longer in the editor so the codeblock cannot
+                // be inspected here. No need to dirty the codeblock since
+                // it has been removed
+                log("removing codeBlock at path " + JSON.stringify(change.position.toJSON()));
+                
+            } else if (((change.type == "remove") || (change.type == "insert")) && 
+                        change.position.parent.is('element', 'codeBlock')) {
+                // Text was added or removed from the codeblock, force a
+                // highlight
+                const codeBlock = change.position.parent;
+                log("dirtying codeBlock " + JSON.stringify(codeBlock.toJSON()));
+                dirtyCodeBlocks.add(codeBlock);
+            }
+        }
+        for (let codeBlock of dirtyCodeBlocks) {
+            highlightCodeBlock(codeBlock, writer);
+        }
+        // Adding markers doesn't modify the document data so no need for
+        // postfixers to run again
+        return false;
+    });
+
+    // This assumes the document is empty and a explicit call to highlight
+    // is not necessary here. Empty documents have a single children of type
+    // paragraph with no text
+    assert((document.getRoot().childCount == 1) && 
+        (document.getRoot().getChild(0).name == "paragraph") &&
+         document.getRoot().getChild(0).isEmpty);
+    
+}
+
+function highlightCodeBlock(codeBlock, writer) {
+    console.log("Highlight code block.");
 }
\ No newline at end of file
diff --git a/src/public/app/widgets/type_widgets/editable_text.js b/src/public/app/widgets/type_widgets/editable_text.js
index 4d1bf82a0..7038cfce7 100644
--- a/src/public/app/widgets/type_widgets/editable_text.js
+++ b/src/public/app/widgets/type_widgets/editable_text.js
@@ -158,7 +158,7 @@ export default class EditableTextTypeWidget extends AbstractTextTypeWidget {
 
         this.watchdog.setCreator(async (elementOrData, editorConfig) => {
             const editor = await BalloonEditor.create(elementOrData, editorConfig);
-            initSyntaxHighlighting();
+            initSyntaxHighlighting(editor);
 
             editor.model.document.on('change:data', () => this.spacedUpdate.scheduleUpdate());