Fix highlighting not updating on new notebooks.

package-lock.json

 {
-  "name": "@pjj56/finesse-syntax-jupyterlab",
-  "version": "0.1.7",
+  "name": "finesse-syntax-jupyterlab",
+  "version": "0.1.8",
   "lockfileVersion": 1,
   "requires": true,
   "dependencies": {

package.json

 {
   "name": "finesse-syntax-jupyterlab",
-  "version": "0.1.7",
+  "version": "0.1.8",
   "description": "Syntax highlighting for kat script within JupyterLab.",
   "keywords": [
     "jupyter",

src/index.ts

@@ -7,7 +7,7 @@ import {
 } from '@jupyterlab/notebook';
 
 import {
-	Cell, CodeCell
+	Cell, CodeCell, ICellModel
 } from '@jupyterlab/cells';
 
 
@@ -24,17 +24,30 @@ function activate(app: JupyterFrontEnd, tracker: INotebookTracker) {
 	tracker.widgetAdded.connect(activate_finesse)
 };
 
-function check_all(sender: Notebook): void {
-	sender.widgets.forEach(cell => {
+function check_all(sender: NotebookPanel): void {
+	sender.content.widgets.forEach(cell => {
 		if (cell instanceof CodeCell && cell.model.mimeType != "text/x-finesse-python") {
 			cell.model.mimeType = "text/x-finesse-python";
 		}
 	});
 };
 
+function set_mime(model: ICellModel) {
+	// Jupyter seems to have some weirdness related to setup of the
+	// mime type of each cell. To avoid having timeouts everywhere,
+	// everytime we select a new cell, we attach a function that checks the
+	// mime type on each content change and sets it if required, otherwise
+	// disconnects itself.
+	if (model.mimeType == "text/x-finesse-python") {
+		model.contentChanged.disconnect(set_mime);
+	} else {
+		model.mimeType = "text/x-finesse-python";
+	}
+}
+
 function check_cell(sender: Notebook, cell: Cell): void {
 	if (cell instanceof CodeCell) {
-		cell.model.mimeType = "text/x-finesse-python";
+		cell.model.contentChanged.connect(set_mime);
 	}
 }
 
@@ -44,7 +57,7 @@ function activate_finesse(sender: INotebookTracker, panel: NotebookPanel): void
 	// I ain't proud of this, but it's the sanest way I could find to get
 	// the syntax highlighting to change on startup without selecting a
 	// different cell
-	setTimeout(() => {check_all(panel.content)}, 500);
+	setTimeout(() => {check_all(panel)}, 500);
 };
 
 export default plugin;