1704403 - eyedropper lies about antialiasing

Status: UNCONFIRMED

(DevTools :: Inspector, defect, P3)

Description

[Andrew Kvapil]

Attachment: visual proof

User Agent: Mozilla/5.0 (X11; Linux x86_64; rv:88.0) Gecko/20100101 Firefox/88.0

Steps to reproduce:

The issue happens with this fontconfig https://pastebin.com/UrB1f4Gk

1. Open Firefox Developer Edition 88.0b8 64-bit on Arch Linux with the Sway window manager (on Wayland) and the above fontconfig
2. Navigate to a website such as https://www.mozilla.org/en-GB/
3. Select the eyedropper from the developer tools menu
4. Hover over text that's been rendered with subpixel rendering

Actual results:

The eyedropper shows the colours as if they were rendered with greyscale anti-aliasing. The provided visual proof is a lossless WebP image, please zoom in to verify that the text is being rendered with subpixel anti-aliasing.

Expected results:

The eyedropper shows the colours as they are displayed on-screen.

Comment 1

[Jan Honza Odvarko [:Honza] (always need-info? me)]

Attachment: image.png

I was testing this on Win 10

1. Loaded https://www.mozilla.org/en-GB/
2. Opening DevTools and using the color picker to inspect the X in the Firefox title
   See the attached image (left side)
3. I also took an OS screenshot of the screen and used Paint to inspect the same pixel
   See the attached image (right side)

There are different colors (compare left and right parts of the attached screenshot)

But not sure whether the test I made is representing the correct way to reproduce a bug.

Honza

Comment 2

[Julian Descottes [:jdescottes]]

Honza, could you also take a screenshot using "Take Screenshot" in the the context menu of Firefox?
This way we can check if this is an issue in the DevTools implementation or in the APIs we use to take screenshots.

Comment 3

[Jan Honza Odvarko [:Honza] (always need-info? me)]

Attachment: image.png

Yes, new screenshot attached.

1. left side - what I see when using the color picker
2. middle - screenshot taken using "Take Screenshot" action in the context menu
3. right - magnified version of #2

Comment 4

[Julian Descottes [:jdescottes]]

Thanks Honza! So the default screenshot feature of Firefox exhibits the same issue.
Although I guess we could argue that the difference is fine for a "screenshot", maybe not for a colorpicker.