Use Map.prototype.getOrInsertComputed in the scripting implementation

This adds a basic non-MOZCENTRAL polyfill for now, which we should be able to remove once the next QuickJS version is released; note the pending changelog at https://github.com/bellard/quickjs/blob/f1139494d18a2053630c5ed3384a42bb70db3c53/Changelog#L7

Author: Snuffleupagus

src/scripting_api/app_utils.js

@@ -26,6 +26,11 @@ function serializeError(error) {
   return { command: "error", value };
 }
 
+// Helpers for simple `Map.prototype.getOrInsertComputed()` invocations,
+// to avoid duplicate function creation.
+const makeArr = () => [];
+const makeMap = () => new Map();
+
 if (typeof PDFJSDev === "undefined" || !PDFJSDev.test("MOZCENTRAL")) {
   // TODO: Remove this once `Math.sumPrecise` is supported in QuickJS.
   //
@@ -36,10 +41,24 @@ if (typeof PDFJSDev === "undefined" || !PDFJSDev.test("MOZCENTRAL")) {
       return numbers.reduce((a, b) => a + b, 0);
     };
   }
+
+  // TODO: Remove this once `Map.prototype.getOrInsertComputed` is supported in
+  // QuickJS.
+  if (typeof Map.prototype.getOrInsertComputed !== "function") {
+    // eslint-disable-next-line no-extend-native
+    Map.prototype.getOrInsertComputed = function (key, callbackFn) {
+      if (!this.has(key)) {
+        this.set(key, callbackFn(key));
+      }
+      return this.get(key);
+    };
+  }
 }
 
 export {
   FORMS_VERSION,
+  makeArr,
+  makeMap,
   serializeError,
   USERACTIVATION_CALLBACKID,
   USERACTIVATION_MAXTIME_VALIDITY,

src/scripting_api/doc.js

@@ -13,10 +13,10 @@
  * limitations under the License.
  */
 
+import { makeArr, makeMap, serializeError } from "./app_utils.js";
 import { createActionsMap } from "./common.js";
 import { PDFObject } from "./pdf_object.js";
 import { PrintParams } from "./print_params.js";
-import { serializeError } from "./app_utils.js";
 import { ZoomType } from "./constants.js";
 
 const DOC_EXTERNAL = false;
@@ -32,6 +32,10 @@ class InfoProxyHandler {
 }
 
 class Doc extends PDFObject {
+  #pageActions = null;
+
+  #otherPageActions = null;
+
   constructor(data) {
     super(data);
 
@@ -96,11 +100,9 @@ class Doc extends PDFObject {
     this._zoom = data.zoom || 100;
     this._actions = createActionsMap(data.actions);
     this._globalEval = data.globalEval;
-    this._pageActions = null;
     this._userActivation = false;
     this._disablePrinting = false;
     this._disableSaving = false;
-    this._otherPageActions = null;
   }
 
   _initActions() {
@@ -170,14 +172,14 @@ class Doc extends PDFObject {
 
   _dispatchPageEvent(name, actions, pageNumber) {
     if (name === "PageOpen") {
-      this._pageActions ||= new Map();
-      if (!this._pageActions.has(pageNumber)) {
-        this._pageActions.set(pageNumber, createActionsMap(actions));
+      this.#pageActions ??= new Map();
+      if (!this.#pageActions.has(pageNumber)) {
+        this.#pageActions.set(pageNumber, createActionsMap(actions));
       }
       this._pageNum = pageNumber - 1;
     }
 
-    for (const acts of [this._pageActions, this._otherPageActions]) {
+    for (const acts of [this.#pageActions, this.#otherPageActions]) {
       actions = acts?.get(pageNumber)?.get(name);
       if (actions) {
         for (const action of actions) {
@@ -212,27 +214,16 @@ class Doc extends PDFObject {
     const po = field.obj._actions.get("PageOpen");
     const pc = field.obj._actions.get("PageClose");
     if (po || pc) {
-      this._otherPageActions ||= new Map();
-      let actions = this._otherPageActions.get(field.obj._page + 1);
-      if (!actions) {
-        actions = new Map();
-        this._otherPageActions.set(field.obj._page + 1, actions);
-      }
+      this.#otherPageActions ??= new Map();
+      const actions = this.#otherPageActions.getOrInsertComputed(
+        field.obj._page + 1,
+        makeMap
+      );
       if (po) {
-        let poActions = actions.get("PageOpen");
-        if (!poActions) {
-          poActions = [];
-          actions.set("PageOpen", poActions);
-        }
-        poActions.push(...po);
+        actions.getOrInsertComputed("PageOpen", makeArr).push(...po);
       }
       if (pc) {
-        let pcActions = actions.get("PageClose");
-        if (!pcActions) {
-          pcActions = [];
-          actions.set("PageClose", pcActions);
-        }
-        pcActions.push(...pc);
+        actions.getOrInsertComputed("PageClose", makeArr).push(...pc);
       }
     }
   }