Create the number tree for the ParentTree only one time

Author: calixteman

src/core/struct_tree.js

@@ -42,6 +42,7 @@ class StructTreeRoot {
     this.roleMap = new Map();
     this.structParentIds = null;
     this.kidRefToPosition = undefined;
+    this.parentTree = null;
   }
 
   getKidPosition(kidRef) {
@@ -70,6 +71,11 @@ class StructTreeRoot {
 
   init() {
     this.readRoleMap();
+    const parentTree = this.dict.get("ParentTree");
+    if (!parentTree) {
+      return;
+    }
+    this.parentTree = new NumberTree(parentTree, this.xref);
   }
 
   #addIdToPage(pageRef, id, type) {
@@ -745,7 +751,7 @@ class StructTreePage {
       return null;
     }
 
-    const parentTree = this.rootDict.get("ParentTree");
+    const { parentTree } = this.root;
     if (!parentTree) {
       return null;
     }
@@ -755,10 +761,9 @@ class StructTreePage {
     }
 
     const map = new Map();
-    const numberTree = new NumberTree(parentTree, this.xref);
 
     for (const [elemId] of ids) {
-      const obj = numberTree.getRaw(elemId);
+      const obj = parentTree.getRaw(elemId);
       if (obj instanceof Ref) {
         map.set(elemId, obj);
       }
@@ -771,7 +776,7 @@ class StructTreePage {
       return;
     }
 
-    const parentTree = this.rootDict.get("ParentTree");
+    const { parentTree } = this.root;
     if (!parentTree) {
       return;
     }
@@ -782,10 +787,9 @@ class StructTreePage {
     }
 
     const map = new Map();
-    const numberTree = new NumberTree(parentTree, this.xref);
 
     if (Number.isInteger(id)) {
-      const parentArray = numberTree.get(id);
+      const parentArray = parentTree.get(id);
       if (Array.isArray(parentArray)) {
         for (const ref of parentArray) {
           if (ref instanceof Ref) {
@@ -799,7 +803,7 @@ class StructTreePage {
       return;
     }
     for (const [elemId, type] of ids) {
-      const obj = numberTree.get(elemId);
+      const obj = parentTree.get(elemId);
       if (obj) {
         const elem = this.addNode(this.xref.fetchIfRef(obj), map);
         if (