[Bug]: Toolbar page number input allows invalid range, causing silent no‑op

Attach (recommended) or Link to PDF file

https://mozilla.github.io/pdf.js/web/compressed.tracemonkey-pldi-09.pdf

Web browser and its version

Firefox 122.0 (64-bit)

Operating system and its version

Ubuntu 22.04 LTS (64-bit)

PDF.js version

Latest (from https://mozilla.github.io/pdf.js/web/viewer.html)

Is the bug present in the latest PDF.js version?

Yes

Is a browser extension

No

Steps to reproduce the problem

1. Open any PDF document in the PDF.js viewer (e.g., https://mozilla.github.io/pdf.js/web/viewer.html?file=compressed.tracemonkey-pldi-09.pdf)
2. Note the total number of pages (e.g., 14 pages)
3. Click on the page number input field in the toolbar
4. Enter an invalid page number:
   • Enter 0 (less than minimum)
   • OR enter a number greater than total pages (e.g., 999)
5. Press Enter key

What is the expected behavior?

he user should receive clear feedback when entering an invalid page number:

Option 1 (Preferred):

• Input field shows a brief visual error indication (red border/background)
• A tooltip or small message appears: "Please enter a page between 1 and 14"
• Input automatically resets to the current page number after 2 seconds

Option 2:

• Input is automatically clamped to valid range
• For 0 → jumps to page 1
• For 999 → jumps to last page (14)

Option 3:

• Dialog/alert notifies user: "Invalid page number. Please enter a number between 1 and 14"

What went wrong?

Actual behavior:

• No visual feedback occurs
• No error message appears
• The viewer silently stays on the current page
• The input field shows the invalid number briefly, then reverts
• User receives no indication that their input was invalid

Why this is problematic:

1. Poor UX - Users are confused why nothing happens
2. Accessibility issue - Screen reader users get no feedback
3. Common mistake - Easy to mistype or forget page count
4. Violates best practices - Form inputs should validate and provide feedback

Link to a viewer

https://mozilla.github.io/pdf.js/web/viewer.html?file=compressed.tracemonkey-pldi-09.pdf

Additional context

Comparison with other PDF viewers

Adobe Acrobat Reader:

• Shows error message: "Please enter a value between 1 and [total]"
• Input field highlights in red

Chrome PDF Viewer:

• Automatically clamps to valid range
• Goes to page 1 if too low, last page if too high

Firefox built-in PDF Viewer:

• Shows inline validation message
• Prevents navigation with invalid input

Foxit Reader:

• Dialog box with error message
• Input field retains focus for correction

Technical Implementation Notes

The issue appears to be in the page number validation logic. Looking at the codebase:

File: web/app.js (around line 3241)

function onPageNumberChanged(evt) {
  const { pdfViewer } = this;
  if (evt.value !== "") {
    this.pdfLinkService.goToPage(evt.value);
  }
  // ... rest of function
}

Start in web/app.js around onPageNumberChanged and reproduce the invalid-input behavior in the PDF.js viewer with values below 1 and above the document length. Determine which stated validation behavior is selected, then verify that invalid input gives feedback or clamps correctly and that valid page navigation still works.