Move some constants and helper functions out of the PartialEvaluator closure

This will simplify the `class` conversion in the next patch, and with modern JavaScript the moved code is still limited to the current module scope.

*Please note:* For improved consistency with our usual formatting, the `TILING_PATTERN`/`SHADING_PATTERN` constants where re-factored slightly.

src/core/evaluator.js

@@ -85,61 +85,23 @@ import { MurmurHash3_64 } from "./murmurhash3.js";
 import { OperatorList } from "./operator_list.js";
 import { PDFImage } from "./image.js";
 
-var PartialEvaluator = (function PartialEvaluatorClosure() {
+const DefaultPartialEvaluatorOptions = Object.freeze({
-  const DefaultPartialEvaluatorOptions = {
   maxImageSize: -1,
   disableFontFace: false,
   ignoreErrors: false,
   isEvalSupported: true,
   fontExtraProperties: false,
-  };
+});
 
-  // eslint-disable-next-line no-shadow
+const PatternType = {
-  function PartialEvaluator({
+  TILING: 1,
-    xref,
+  SHADING: 2,
-    handler,
+};
-    pageIndex,
-    idFactory,
-    fontCache,
-    builtInCMapCache,
-    globalImageCache,
-    options = null,
-  }) {
-    this.xref = xref;
-    this.handler = handler;
-    this.pageIndex = pageIndex;
-    this.idFactory = idFactory;
-    this.fontCache = fontCache;
-    this.builtInCMapCache = builtInCMapCache;
-    this.globalImageCache = globalImageCache;
-    this.options = options || DefaultPartialEvaluatorOptions;
-    this.parsingType3Font = false;
 
-    this._fetchBuiltInCMapBound = this.fetchBuiltInCMap.bind(this);
+const deferred = Promise.resolve();
-  }
 
-  // Trying to minimize Date.now() usage and check every 100 time
+// Convert PDF blend mode names to HTML5 blend mode names.
-  var TIME_SLOT_DURATION_MS = 20;
+function normalizeBlendMode(value, parsingArray = false) {
-  var CHECK_TIME_EVERY = 100;
-  function TimeSlotManager() {
-    this.reset();
-  }
-  TimeSlotManager.prototype = {
-    check: function TimeSlotManager_check() {
-      if (++this.checked < CHECK_TIME_EVERY) {
-        return false;
-      }
-      this.checked = 0;
-      return this.endTime <= Date.now();
-    },
-    reset: function TimeSlotManager_reset() {
-      this.endTime = Date.now() + TIME_SLOT_DURATION_MS;
-      this.checked = 0;
-    },
-  };
-
-  // Convert PDF blend mode names to HTML5 blend mode names.
-  function normalizeBlendMode(value, parsingArray = false) {
   if (Array.isArray(value)) {
     // Use the first *supported* BM value in the Array (fixes issue11279.pdf).
     for (let i = 0, ii = value.length; i < ii; i++) {
@@ -198,12 +160,52 @@ var PartialEvaluator = (function PartialEvaluatorClosure() {
   }
   warn(`Unsupported blend mode: ${value.name}`);
   return "source-over";
+}
+
+// Trying to minimize Date.now() usage and check every 100 time.
+var TIME_SLOT_DURATION_MS = 20;
+var CHECK_TIME_EVERY = 100;
+function TimeSlotManager() {
+  this.reset();
+}
+TimeSlotManager.prototype = {
+  check: function TimeSlotManager_check() {
+    if (++this.checked < CHECK_TIME_EVERY) {
+      return false;
     }
+    this.checked = 0;
+    return this.endTime <= Date.now();
+  },
+  reset: function TimeSlotManager_reset() {
+    this.endTime = Date.now() + TIME_SLOT_DURATION_MS;
+    this.checked = 0;
+  },
+};
 
-  var deferred = Promise.resolve();
+var PartialEvaluator = (function PartialEvaluatorClosure() {
+  // eslint-disable-next-line no-shadow
+  function PartialEvaluator({
+    xref,
+    handler,
+    pageIndex,
+    idFactory,
+    fontCache,
+    builtInCMapCache,
+    globalImageCache,
+    options = null,
+  }) {
+    this.xref = xref;
+    this.handler = handler;
+    this.pageIndex = pageIndex;
+    this.idFactory = idFactory;
+    this.fontCache = fontCache;
+    this.builtInCMapCache = builtInCMapCache;
+    this.globalImageCache = globalImageCache;
+    this.options = options || DefaultPartialEvaluatorOptions;
+    this.parsingType3Font = false;
 
-  var TILING_PATTERN = 1,
+    this._fetchBuiltInCMapBound = this.fetchBuiltInCMap.bind(this);
-    SHADING_PATTERN = 2;
+  }
 
   PartialEvaluator.prototype = {
     /**
@@ -1193,7 +1195,7 @@ var PartialEvaluator = (function PartialEvaluatorClosure() {
         var dict = isStream(pattern) ? pattern.dict : pattern;
         var typeNum = dict.get("PatternType");
 
-        if (typeNum === TILING_PATTERN) {
+        if (typeNum === PatternType.TILING) {
           var color = cs.base ? cs.base.getRgb(args, 0) : null;
           return this.handleTilingType(
             fn,
@@ -1204,7 +1206,7 @@ var PartialEvaluator = (function PartialEvaluatorClosure() {
             operatorList,
             task
           );
-        } else if (typeNum === SHADING_PATTERN) {
+        } else if (typeNum === PatternType.SHADING) {
           var shading = dict.get("Shading");
           var matrix = dict.getArray("Matrix");
           pattern = Pattern.parseShading(