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Re: [csswg-drafts] [resize-observer] device-pixel-border-box size (#3554)

From: Chris Harrelson via GitHub <sysbot+gh@w3.org>
Date: Fri, 04 Oct 2019 16:17:01 +0000
To: public-css-archive@w3.org
Message-ID: <issue_comment.created-538464995-1570205820-sysbot+gh@w3.org>
Here is a demo page that clearly shows the issue:

https://output.jsbin.com/gemipizazi/1

If you load this in Chrome Canary with the --enable-use-zoom-for-dsf command-line flag (*), and resize the browser window vertically, there will be a number of visual artifacts in the rendering, that appear or disappear according to the different pixel snapping that happens with different viewport heights.

If you load the same demo in Safari Technical Preview with the experimental ResizeObserver turned on, and resize the browser vertically, you'll see the same kind of artifacts (but different ones, because the pixel snapping algorithm depends on the browser).

If you apply a hacked-up prototype of the device pixel border box observation feature to Chromium via patching [this CL](https://chromium-review.googlesource.com/c/chromium/src/+/1832602) then the rendering artifacts are gone.

I tested these on a Retina MacBook Pro.

(*) This flag turns on pixel snapping at device pixel granularity, rather than CSS pixel granularity. This flag has already been shipped in Chrome on all platforms except for Mac, and will ship on Mac soon. It's also a necessary feature for high quality output, but orthogonal & complementary to the issue being discussed here.

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Please view or discuss this issue at https://github.com/w3c/csswg-drafts/issues/3554#issuecomment-538464995 using your GitHub account
Received on Friday, 4 October 2019 16:17:03 UTC

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