Fix menu to not rerender if no typesetting has occurred. (mathjax/MathJax#3167)

ts/components/startup.ts

@@ -96,6 +96,7 @@ export interface MathJaxObject extends MJObject {
     elements: any[];
     document: MATHDOCUMENT;
     promise: Promise<void>;
+    rerenderPromise: Promise<void>;
     /* tslint:disable:jsdoc-require */
     registerConstructor(name: string, constructor: any): void;
     useHandler(name: string, force?: boolean): void;
@@ -184,7 +185,7 @@ export namespace Startup {
 
   /**
    * The promise for the startup process (the initial typesetting).
-   * It is resolves or rejected in the ready() function.
+   * It is resolved or rejected in the ready() function.
    */
   export let promise = new Promise<void>((resolve, reject) => {
     promiseResolve = resolve;
@@ -206,6 +207,13 @@ export namespace Startup {
     }
   });
 
+  /**
+   * Non-null when MathJax.typeset() or MathJax.typesetPromise() have been performed
+   * (so the menu code can tell whether a rerender is needed when components are loaded)
+   * and then is equal to a promise after which rerendering can occur.
+   */
+  export let rerenderPromise: Promise<void> = null;
+
   /**
    * @param {MmlNode} node   The root of the tree to convert to serialized MathML
    * @return {string}        The serialized MathML from the tree
@@ -374,9 +382,12 @@ export namespace Startup {
       document.options.elements = elements;
       document.reset();
       document.render();
+      if (!rerenderPromise) {
+        rerenderPromise = promise;
+      }
     };
     MathJax.typesetPromise = (elements: any[] = null) => {
-      promise = promise.then(() => typesetPromise(elements));
+      rerenderPromise = promise = promise.then(() => typesetPromise(elements));
       return promise;
     };
     MathJax.typesetClear = (elements: any[] = null) => {

ts/ui/menu/Menu.ts

@@ -1175,18 +1175,23 @@ export class Menu {
 
   /**
    * Rerender the output if we aren't in the middle of loading a new component
-   *   (in which case, we will rerender in the callback performed  after it is loaded)
+   *   (in which case, we will rerender in the callback performed after it is loaded)
    *
    * @param {number=} start   The state at which to start rerendering
    */
   protected rerender(start: number = STATE.TYPESET) {
     this.rerenderStart = Math.min(start, this.rerenderStart);
-    if (!Menu.loading) {
-      if (this.rerenderStart <= STATE.COMPILED) {
-        this.document.reset({inputJax: []});
-      }
-      this.document.rerender(this.rerenderStart);
-      this.rerenderStart = STATE.LAST;
+    const startup = MathJax.startup;
+    if (!Menu.loading && startup.rerenderPromise) {
+      startup.rerenderPromise = startup.promise = startup.rerenderPromise.then(
+        () => mathjax.handleRetriesFor(() => {
+          if (this.rerenderStart <= STATE.COMPILED) {
+            this.document.reset({inputJax: []});
+          }
+          this.document.rerender(this.rerenderStart);
+          this.rerenderStart = STATE.LAST;
+        })
+      );
     }
   }