Always render cursor even if model didn't change

This ensures underline/bar cursors get rendered

addons/xterm-addon-webgl/src/RectangleRenderer.ts

@@ -242,11 +242,9 @@ export class RectangleRenderer extends Disposable {
       }
     }
     vertices.count = rectangleCount;
-
-    this._updateCursor(model);
   }
 
-  private _updateCursor(model: IRenderModel): void {
+  public updateCursor(model: IRenderModel): void {
     const vertices = this._verticesCursor;
     const cursor = model.cursor;
     if (!cursor || cursor.style === 'block') {

addons/xterm-addon-webgl/src/WebglRenderer.ts

@@ -523,6 +523,7 @@ export class WebglRenderer extends Disposable implements IRenderer {
     if (modelUpdated) {
       this._rectangleRenderer!.updateBackgrounds(this._model);
     }
+    this._rectangleRenderer!.updateCursor(this._model);
   }
 
   /**