[api-minor] Change the format of the fontName-property, in defaultAppearanceData, on Annotation-instances (PR 12831 follow-up)

Currently the `fontName`-property contains an actual /Name-instance, which is a problem given that its fallback value is an empty string; see ca7f546828/src/core/default_appearance.js (L35)
The reason that this is a problem can be seen in ca7f546828/src/core/primitives.js (L30-L34), since an empty string short-circuits the cache. Essentially, in PDF documents, a /Name-instance cannot be empty and the way that the `DefaultAppearanceEvaluator` does things is unfortunately not entirely correct.

Hence the `fontName`-property is changed to instead contain a string, rather than a /Name-instance, which simplifies the code overall.

*Please note:* I'm tagging this patch with "[api-minor]", since PR 12831 is included in the current pre-release (although we're not using the `fontName`-property in the display-layer).

src/core/annotation.js

@@ -1470,7 +1470,7 @@ class WidgetAnnotation extends Annotation {
     const { fontName, fontSize } = this.data.defaultAppearanceData;
     await evaluator.handleSetFont(
       this._fieldResources.mergedResources,
-      [fontName, fontSize],
+      [fontName && Name.get(fontName), fontSize],
       /* fontRef = */ null,
       operatorList,
       task,
@@ -1565,26 +1565,26 @@ class WidgetAnnotation extends Annotation {
       acroFormResources,
     } = this._fieldResources;
 
-    const fontNameStr =
+    const fontName =
       this.data.defaultAppearanceData &&
-      this.data.defaultAppearanceData.fontName.name;
-    if (!fontNameStr) {
+      this.data.defaultAppearanceData.fontName;
+    if (!fontName) {
       return localResources || Dict.empty;
     }
 
     for (const resources of [localResources, appearanceResources]) {
       if (resources instanceof Dict) {
         const localFont = resources.get("Font");
-        if (localFont instanceof Dict && localFont.has(fontNameStr)) {
+        if (localFont instanceof Dict && localFont.has(fontName)) {
           return resources;
         }
       }
     }
     if (acroFormResources instanceof Dict) {
       const acroFormFont = acroFormResources.get("Font");
-      if (acroFormFont instanceof Dict && acroFormFont.has(fontNameStr)) {
+      if (acroFormFont instanceof Dict && acroFormFont.has(fontName)) {
         const subFontDict = new Dict(xref);
-        subFontDict.set(fontNameStr, acroFormFont.getRaw(fontNameStr));
+        subFontDict.set(fontName, acroFormFont.getRaw(fontName));
 
         const subResourcesDict = new Dict(xref);
         subResourcesDict.set("Font", subFontDict);

src/core/default_appearance.js

@@ -13,11 +13,11 @@
  * limitations under the License.
  */
 
-import { isName, Name } from "./primitives.js";
 import { OPS, warn } from "../shared/util.js";
 import { ColorSpace } from "./colorspace.js";
 import { escapePDFName } from "./core_utils.js";
 import { EvaluatorPreprocessor } from "./evaluator.js";
+import { Name } from "./primitives.js";
 import { StringStream } from "./stream.js";
 
 class DefaultAppearanceEvaluator extends EvaluatorPreprocessor {
@@ -32,8 +32,8 @@ class DefaultAppearanceEvaluator extends EvaluatorPreprocessor {
     };
     const result = {
       fontSize: 0,
-      fontName: Name.get(""),
-      fontColor: new Uint8ClampedArray([0, 0, 0]) /* black */,
+      fontName: "",
+      fontColor: /* black = */ new Uint8ClampedArray(3),
     };
 
     try {
@@ -51,8 +51,8 @@ class DefaultAppearanceEvaluator extends EvaluatorPreprocessor {
         switch (fn | 0) {
           case OPS.setFont:
             const [fontName, fontSize] = args;
-            if (isName(fontName)) {
-              result.fontName = fontName;
+            if (fontName instanceof Name) {
+              result.fontName = fontName.name;
             }
             if (typeof fontSize === "number" && fontSize > 0) {
               result.fontSize = fontSize;
@@ -93,7 +93,7 @@ function createDefaultAppearance({ fontSize, fontName, fontColor }) {
         .map(c => (c / 255).toFixed(2))
         .join(" ") + " rg";
   }
-  return `/${escapePDFName(fontName.name)} ${fontSize} Tf ${colorCmd}`;
+  return `/${escapePDFName(fontName)} ${fontSize} Tf ${colorCmd}`;
 }
 
 export { createDefaultAppearance, parseDefaultAppearance };

src/core/evaluator.js

@@ -794,12 +794,8 @@ class PartialEvaluator {
     state,
     fallbackFontDict = null
   ) {
-    // TODO(mack): Not needed?
-    var fontName;
-    if (fontArgs) {
-      fontArgs = fontArgs.slice();
-      fontName = fontArgs[0].name;
-    }
+    const fontName =
+      fontArgs && fontArgs[0] instanceof Name ? fontArgs[0].name : null;
 
     return this.loadFont(fontName, fontRef, resources, fallbackFontDict)
       .then(translated => {