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Issue metadata

Status: Available
Owner: ----
Cc:
Components:
EstimatedDays: ----
NextAction: ----
OS: Linux , Android , Windows , All , Chrome , Mac
Pri: 2
Type: Bug



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box-shadow sometimes disables subpixel text AA

Reported by a...@scirra.com, Jan 4 2017

Issue description

UserAgent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/57.0.2971.0 Safari/537.36

Steps to reproduce the problem:
1. Visit https://www.scirra.com/labs/bugs/cleartypebug/ (note using Windows 10 with low-dpi display and cleartype enabled)
2. View the four boxes. Take a screenshot and zoom in.

What is the expected behavior?
Subpixel text antialiasing in all four cases.

What went wrong?
Case 4 reverts to grayscale antialiasing. Enlarged screenshot of what I see: https://www.scirra.com/labs/bugs/cleartypebug/observed.png

Did this work before? No 

Does this work in other browsers? Yes

Chrome version: 57.0.2971.0  Channel: canary
OS Version: 10.0
Flash Version: Shockwave Flash 24.0 r0

The four cases are:

(1) no special styles
(2) has a box-shadow
(3) has will-change: transform
(4) has both a box shadow and will-change: transform

It seems odd that adding a box-shadow to case (3) causes text to display with lower quality, given that box-shadow only renders outside the element box. Why should it affect the quality of the content inside the box?

Edge and Firefox render all 4 cases with subpixel AA, so this issue is specific to Chrome.
 

Comment 1 by suzyh@chromium.org, Jan 4 2017

Components: -Blink>CSS Blink>Paint
will-change: transform causes things to go through a different rendering path. Passing over to the Paint folks to take a look.
Labels: Needs-Triage-M57
Cc: flackr@chromium.org smcgruer@chromium.org
Components: Blink>Compositing
Labels: -OS-Windows OS-All
Status: Available (was: Unconfirmed)
Confirmed on Linux too in M56. I agree that the box shadow should not affect the text in this case, and it's also unclear why having it's own backing would change the behavior. It may be that we are not special casing a general requirement.

Thanks for the good test case.
Labels: -Needs-Triage-M57 M-58
Able to reproduce the issue on Win 10 using latest canary 58.0.3019.0.
This is a non-regression issue since 40.0.2214.115 on Win 7 and Win 10, Mac 10.12.3 and Ubuntu 14.04.
Project Member

Comment 5 by sheriffbot@chromium.org, Feb 21 2018

Labels: Hotlist-Recharge-Cold
Status: Untriaged (was: Available)
This issue has been Available for over a year. If it's no longer important or seems unlikely to be fixed, please consider closing it out. If it is important, please re-triage the issue.

Sorry for the inconvenience if the bug really should have been left as Available. If you change it back, also remove the "Hotlist-Recharge-Cold" label.

For more details visit https://www.chromium.org/issue-tracking/autotriage - Your friendly Sheriffbot
Labels: -Hotlist-Recharge-Cold OS-Android OS-Chrome OS-Linux OS-Mac OS-Windows
Status: Available (was: Untriaged)
Still happens, and no time to investigate why.

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