fix: respect capture_on_queue in WebcamCapture.IS_CHANGED

[mango766]

Fixes #13337

What's wrong

WebcamCapture has a capture_on_queue input (default True) that's supposed to force a new webcam capture every time a prompt is queued. But IS_CHANGED just delegates to the parent's file-hash check and never looks at the flag:

# before
@classmethod
def IS_CHANGED(cls, image, width, height, capture_on_queue):
    return super().IS_CHANGED(image)  # capture_on_queue silently ignored

Because IS_CHANGED returns the same SHA-256 hash when the on-disk image hasn't changed, ComfyUI's caching layer skips re-executing the node — so live webcam feeds appear to freeze even with capture_on_queue=True.

Fix

Return float("NaN") when capture_on_queue is True, which tells the scheduler the node is always dirty and must run again. Fall back to the hash comparison only when the flag is off.

# after
@classmethod
def IS_CHANGED(cls, image, width, height, capture_on_queue):
    if capture_on_queue:
        return float("NaN")
    return super().IS_CHANGED(image)

One-line change, no new dependencies.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Path: .coderabbit.yaml

Review profile: CHILL

Plan: Pro

Run ID: 0a1b9bc0-a5f7-4546-951c-d5abcc1d0f6e

📥 Commits

Reviewing files that changed from the base of the PR and between 2d861fb and 197dba5.

📒 Files selected for processing (2)

• comfy_extras/nodes_webcam.py
• server.py

---

📝 Walkthrough

Walkthrough

This pull request modifies two files with distinct purposes. In comfy_extras/nodes_webcam.py, the WebcamCapture.IS_CHANGED() method adds conditional logic to return float("NaN") when capture_on_queue is True, while preserving existing behavior when False. In server.py, the mask image upload handling is refactored to use a context manager for opening mask images, ensuring deterministic file handle closure during the image conversion process.

🚥 Pre-merge checks | ✅ 3 | ❌ 2

❌ Failed checks (2 warnings)

Check name	Status	Explanation	Resolution
Out of Scope Changes check	⚠️ Warning	Changes to server.py (unclosed file handle fix) appear unrelated to issue #13337, which focuses solely on WebcamCapture.IS_CHANGED behavior.	Remove the server.py mask image file-handle fix or create a separate PR, as it's outside the scope of the capture_on_queue issue.
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (3 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly and specifically identifies the main change: fixing WebcamCapture.IS_CHANGED to respect the capture_on_queue flag.
Description check	✅ Passed	The description is directly related to the changeset, explaining the bug, the fix, and providing before/after code examples.
Linked Issues check	✅ Passed	The PR successfully implements the fix described in issue #13337: IS_CHANGED now returns float('NaN') when capture_on_queue is True, forcing re-execution.

_{✏️ Tip: You can configure your own custom pre-merge checks in the settings.}

---

Thanks for using CodeRabbit! It's free for OSS, and your support helps us grow. If you like it, consider giving us a shout-out.

❤️ Share

• X
• Mastodon
• Reddit
• LinkedIn

_{Comment @coderabbitai help to get the list of available commands and usage tips.}