Combine the getPathJs and hasBuiltPath methods in the CompiledFont class

This avoids duplicating the charCode/glyphId lookup, and (slightly) shortens the code. In particular:
 - Given that the path-data is returned as a TypedArray, it's easy enough to instead return `null` to indicate that the glyph was previously compiled.

 - The charCode-cache can be changed into a Set, since we only need to track the "seen" charCodes and not their relation to the glyphIds.

 - The `compileFontPathInfo` call is moved into `CompiledFont` class, since that simplifies the `src/core/evaluator.js` code a tiny bit.

src/core/evaluator.js

@@ -33,10 +33,6 @@ import {
 import { CheckedOperatorList, OperatorList } from "./operator_list.js";
 import { CMapFactory, IdentityCMap } from "./cmap.js";
 import { Cmd, Dict, EOF, isName, Name, Ref, RefSet } from "./primitives.js";
-import {
-  compileFontPathInfo,
-  compilePatternInfo,
-} from "./obj_bin_transform_core.js";
 import {
   compileType3Glyph,
   FontFlags,
@@ -83,6 +79,7 @@ import { BaseStream } from "./base_stream.js";
 import { bidi } from "./bidi.js";
 import { ColorSpace } from "./colorspace.js";
 import { ColorSpaceUtils } from "./colorspace_utils.js";
+import { compilePatternInfo } from "./obj_bin_transform_core.js";
 import { getFontSubstitution } from "./font_substitutions.js";
 import { getGlyphsUnicode } from "./glyphlist.js";
 import { getMetrics } from "./metrics.js";
@@ -4809,10 +4806,10 @@ class PartialEvaluator {
     function buildPath(fontChar) {
       const glyphName = `${font.loadedName}_path_${fontChar}`;
       try {
-        if (font.renderer.hasBuiltPath(fontChar)) {
+        const buffer = font.renderer.getPath(fontChar);
-          return;
+        if (!buffer) {
+          return; // Previously compiled, and sent to the main-thread.
         }
-        const buffer = compileFontPathInfo(font.renderer.getPathJs(fontChar));
         handler.send("commonobj", [glyphName, "FontPath", buffer], [buffer]);
       } catch (reason) {
         if (evaluatorOptions.ignoreErrors) {

src/core/font_renderer.js

@@ -26,6 +26,7 @@ import {
   warn,
 } from "../shared/util.js";
 import { CFFParser } from "./cff_parser.js";
+import { compileFontPathInfo } from "./obj_bin_transform_core.js";
 import { getGlyphsUnicode } from "./glyphlist.js";
 import { isNumberArray } from "./core_utils.js";
 import { StandardEncoding } from "./encodings.js";
@@ -781,9 +782,9 @@ class Commands {
 }
 
 class CompiledFont {
-  #compiledGlyphs = new Map();
+  #compiledCharCodes = new Set();
 
-  #compiledCharCodeToGlyphId = new Map();
+  #compiledGlyphs = new Map();
 
   constructor(fontMatrix) {
     if (
@@ -806,9 +807,16 @@ class CompiledFont {
     );
   }
 
-  getPathJs(unicode) {
+  getPath(unicode) {
     const { charCode, glyphId } = lookupCmap(this.cmap, unicode);
 
+    if (
+      this.#compiledGlyphs.has(glyphId) &&
+      this.#compiledCharCodes.has(charCode)
+    ) {
+      return null; // Previously compiled.
+    }
+
     const path = this.#compiledGlyphs.getOrInsertComputed(glyphId, () => {
       try {
         return this.compileGlyph(this.glyphs[glyphId], glyphId);
@@ -816,12 +824,12 @@ class CompiledFont {
         return ex; // Avoid attempting to re-compile a corrupt glyph.
       }
     });
-    this.#compiledCharCodeToGlyphId.getOrInsert(charCode, glyphId);
+    this.#compiledCharCodes.add(charCode);
 
     if (path instanceof Error) {
       throw path;
     }
-    return path;
+    return compileFontPathInfo(path);
   }
 
   compileGlyph(code, glyphId) {
@@ -854,14 +862,6 @@ class CompiledFont {
   compileGlyphImpl() {
     unreachable("Children classes should implement this.");
   }
-
-  hasBuiltPath(unicode) {
-    const { charCode, glyphId } = lookupCmap(this.cmap, unicode);
-    return (
-      this.#compiledGlyphs.has(glyphId) &&
-      this.#compiledCharCodeToGlyphId.has(charCode)
-    );
-  }
 }
 
 class TrueTypeCompiled extends CompiledFont {