Ensure that all necessary /Font resources are included when saving a …

…`WidgetAnnotation`-instance (issue 12294)

This patch contains a possible approach for fixing issue 12294, which compared to other PRs is purposely limited to the affected `WidgetAnnotation` code.

As mentioned elsewhere, considering that we're (at least for now) trying to fix *one specific* case, I think that we should avoid modifying the `Dict` primitive[1] and/or avoid a solution that (indirectly) modifies an existing `Dict`-instance[2].
This patch simply fixes the issue at hand, since that seems easiest for now, and I'd suggest that we worry about a more general approach if/when that actually becomes necessary.

Hence the solution implemented here, for `WidgetAnnotation`, is to simply use a combination of the local *and* AcroForm /DR resources during OperatorList-parsing to ensure that things work correctly regardless of where a particular /Font resource is found.
For saving of form-data, on the other hand, we want to avoid increasing the file-size unnecessarily and need to be smarter than just merging all of the available resources. To achive this, a new `WidgetAnnotation._getSaveFieldResources` method will when necessary produce a combined resources `Dict` with only the minimum amount of data from the AcroForm /DR resources included.

---
[1] You want to avoid anything that could cause the general `Dict` implementation to become slower, or more complex, just for handling an edge-case in my opinion.

[2] If an existing `Dict`-instance is modified unexpectedly, that could very easily lead to problems elsewhere since e.g. `Dict`-instances created during parsing are not expected to be changed.

src/core/annotation.js

@@ -885,10 +885,18 @@ class WidgetAnnotation extends Annotation {
  "";
  const fieldType = getInheritableProperty({ dict, key: "FT" });
  data.fieldType = isName(fieldType) ? fieldType.name : null;
- this.fieldResources =
- getInheritableProperty({ dict, key: "DR" }) ||
- params.acroForm.get("DR") ||
- Dict.empty;
+
+ const localResources = getInheritableProperty({ dict, key: "DR" });
+ const acroFormResources = params.acroForm.get("DR");
+ this._fieldResources = {
+ localResources,
+ acroFormResources,
+ mergedResources: Dict.merge({
+ xref: params.xref,
+ dictArray: [localResources, acroFormResources],
+ mergeSubDicts: true,
+ }),
+ };
 
  data.fieldFlags = getInheritableProperty({ dict, key: "Ff" });
  if (!Number.isInteger(data.fieldFlags) || data.fieldFlags < 0) {
@@ -1043,7 +1051,7 @@ class WidgetAnnotation extends Annotation {
  .getOperatorList({
  stream,
  task,
- resources: this.fieldResources,
+ resources: this._fieldResources.mergedResources,
  operatorList,
  })
  .then(function () {
@@ -1067,8 +1075,9 @@ class WidgetAnnotation extends Annotation {
  if (appearance === null) {
  return null;
  }
+ const { xref } = evaluator;
 
- const dict = evaluator.xref.fetchIfRef(this.ref);
+ const dict = xref.fetchIfRef(this.ref);
  if (!isDict(dict)) {
  return null;
  }
@@ -1086,11 +1095,11 @@ class WidgetAnnotation extends Annotation {
  value,
  };
 
- const newRef = evaluator.xref.getNewRef();
- const AP = new Dict(evaluator.xref);
+ const newRef = xref.getNewRef();
+ const AP = new Dict(xref);
  AP.set("N", newRef);
 
- const encrypt = evaluator.xref.encrypt;
+ const encrypt = xref.encrypt;
  let originalTransform = null;
  let newTransform = null;
  if (encrypt) {
@@ -1106,10 +1115,10 @@ class WidgetAnnotation extends Annotation {
  dict.set("AP", AP);
  dict.set("M", `D:${getModificationDate()}`);
 
- const appearanceDict = new Dict(evaluator.xref);
+ const appearanceDict = new Dict(xref);
  appearanceDict.set("Length", appearance.length);
  appearanceDict.set("Subtype", Name.get("Form"));
- appearanceDict.set("Resources", this.fieldResources);
+ appearanceDict.set("Resources", this._getSaveFieldResources(xref));
  appearanceDict.set("BBox", bbox);
 
  const bufferOriginal = [`${this.ref.num} ${this.ref.gen} obj\n`];
@@ -1132,6 +1141,8 @@ class WidgetAnnotation extends Annotation {
  }
 
  async _getAppearance(evaluator, task, annotationStorage) {
+ this._fontName = null;
+
  const isPassword = this.hasFieldFlag(AnnotationFieldFlag.PASSWORD);
  if (!annotationStorage || isPassword) {
  return null;
@@ -1148,9 +1159,8 @@ class WidgetAnnotation extends Annotation {
 
  const fontInfo = await this._getFontData(evaluator, task);
  const [font, fontName] = fontInfo;
- let fontSize = fontInfo[2];
-
- fontSize = this._computeFontSize(font, fontName, fontSize, totalHeight);
+ const fontSize = this._computeFontSize(...fontInfo, totalHeight);
+ this._fontName = fontName;
 
  let descent = font.descent;
  if (isNaN(descent)) {
@@ -1226,7 +1236,7 @@ class WidgetAnnotation extends Annotation {
  await evaluator.getOperatorList({
  stream: new StringStream(this.data.defaultAppearance),
  task,
- resources: this.fieldResources,
+ resources: this._fieldResources.mergedResources,
  operatorList,
  initialState,
  });
@@ -1280,6 +1290,49 @@ class WidgetAnnotation extends Annotation {
 
  return `${shift} ${vPadding} Td (${escapeString(text)}) Tj`;
  }
+
+ /**
+ * @private
+ */
+ _getSaveFieldResources(xref) {
+ if (
+ typeof PDFJSDev === "undefined" ||
+ PDFJSDev.test("!PRODUCTION || TESTING")
+ ) {
+ assert(
+ this._fontName !== undefined,
+ "Expected `_getAppearance()` to have been called."
+ );
+ }
+ const { localResources, acroFormResources } = this._fieldResources;
+
+ if (!this._fontName) {
+ return localResources || Dict.empty;
+ }
+ if (localResources instanceof Dict) {
+ const localFont = localResources.get("Font");
+ if (localFont instanceof Dict && localFont.has(this._fontName)) {
+ return localResources;
+ }
+ }
+ if (acroFormResources instanceof Dict) {
+ const acroFormFont = acroFormResources.get("Font");
+ if (acroFormFont instanceof Dict && acroFormFont.has(this._fontName)) {
+ const subFontDict = new Dict(xref);
+ subFontDict.set(this._fontName, acroFormFont.getRaw(this._fontName));
+
+ const subResourcesDict = new Dict(xref);
+ subResourcesDict.set("Font", subFontDict);
+
+ return Dict.merge({
+ xref,
+ dictArray: [subResourcesDict, localResources],
+ mergeSubDicts: true,
+ });
+ }
+ }
+ return localResources || Dict.empty;
+ }
 }
 
 class TextWidgetAnnotation extends WidgetAnnotation {