mozilla/pdf.js · error · Error

app.printerNames is read-only

Error message

app.printerNames is read-only

What it means

app.printerNames returns an empty array because PDF.js does not enumerate system printers. The list is viewer-managed and read-only; the setter throws. Assignment is rejected unconditionally.

Source

Thrown at src/scripting_api/app.js:322

  set plugins(_) {
    throw new Error("app.plugins is read-only");
  }

  get printColorProfiles() {
    return [];
  }

  set printColorProfiles(_) {
    throw new Error("app.printColorProfiles is read-only");
  }

  get printerNames() {
    return [];
  }

  set printerNames(_) {
    throw new Error("app.printerNames is read-only");
  }

  get runtimeHighlight() {
    return this._runtimeHighlight;
  }

  set runtimeHighlight(val) {
    this._runtimeHighlight = val;
    /* TODO */
  }

  get runtimeHighlightColor() {
    return this._runtimeHighlightColor;
  }

  set runtimeHighlightColor(val) {
    if (Color._isValidColor(val)) {
      this._runtimeHighlightColor = val;

View on GitHub (pinned to 5903d58d58)

Solutions

1. Read app.printerNames only; expect [].
2. Use the host browser's print dialog for printer selection.
3. Do not attempt to push printer names from document scripts.

Example fix

// before
app.printerNames = ['Printer1'];
// after
const printers = app.printerNames; // [] in pdf.js

// app.printerNames always returns [] in pdf.js.
const knownPrinters = (app) => app.printerNames;

const isPrinterList = (v) => Array.isArray(v);

try { /* code that may assign app.printerNames */ }
catch (e) { if (!/printerNames is read-only/.test(e.message)) throw e; }

When it happens

Trigger: Any assignment app.printerNames = [...] in PDF JavaScript or caller code hits the throw at src/scripting_api/app.js:322.

Common situations: Scripts trying to pre-populate a print target list; print dialogs expecting a writable registry.

Related errors

• app.printColorProfiles is read-only
• app.fromPDFConverters is read-only
• app.monitors is read-only
• app.numPlugins is read-only
• app.plugins is read-only

AI-assisted analysis of mozilla/pdf.js@5903d58d58 (2026-08-13). Data as JSON: /api/errors/648c956daeac96c4. Report an issue: GitHub.