Page renders incorrectly due to scaling / calc() issues

External Issue #11008616


Jonas T.
Feb 20, 2017
This issue is public.
Found in
  • Microsoft Edge
Reported by 2 people

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Steps to reproduce

The page renders incorrectly due to scaling / calc() issues. I think it is potentially related to the use of CSS variables which might not be processed correctly.

To see how the page is supposed to look like, use Chromium >= 55 (latest regular release), or Firefox >= 51 (latest regular release). I attached an image named broken.jpg with the faulty Edge rendering, and an attachment named correct.png with the Firefox rendering.

Similar issue observed on URL :


Comments and activity

  • Changed Steps to Reproduce

  • Gmail shows the same problem, only in Edge. Opera, Firefox, Chrome, Brave… correct rendering. Edge? Broken.

  • Microsoft Edge Team

    Changed Assigned To to “Brad E.”

    Changed Assigned To from “Brad E.” to “Steven K.”

  • Changed Steps to Reproduce

  • I changed the homepage link to since we moved to another address. However, the rendering issue remains.

  • I think a potentially related issue with calc is that it looks like edge is using Math.round instead of Math.floor when calculating sizes. This causes unintended overflow in some situations.

    I’ve added a couple of screen shots (calc-good and calc-bad). They are both the exact same CSS, all I was doing was resizing the browser window 1 pixel of difference. The items are set as width: calc(100vw / 3) which works properly in all other browsers. The resizing of the window intermittently causing the issue is what leads me to believe this is caused by a rounding error.

  • Microsoft Edge Team

    Changed Assigned To to “Rick J.”

    Changed Steps to Reproduce

    Changed Assigned To to “Rick J.”

    Changed Steps to Reproduce

    Changed Steps to Reproduce

    Changed Assigned To to “Bogdan B.”

    Changed Status to “External”

  • Thanks for your bug report! Edge does not support calc() in rotate and scale, so that would make sense.

  • This issue has been resolved External. This means this issue may require a new feature to be implemented or other work that is more significant than a typical bug. You may be able to find more information on this issue by searching for related features on and

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