[Webkit-unassigned] [Bug 195401] New: Transform scale() combined with a devicePixelRatio creates roundoff errors

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=195401

            Bug ID: 195401
           Summary: Transform scale() combined with a devicePixelRatio
                    creates roundoff errors
           Product: WebKit
           Version: Safari 12
          Hardware: All
                OS: All
            Status: NEW
          Severity: Normal
          Priority: P2
         Component: Accessibility
          Assignee: webkit-unassigned at lists.webkit.org
          Reporter: tomdezentje at gmail.com
                CC: webkit-bug-importer at group.apple.com

When a browser has a devicePixelRatio with decimals there seems to be a roundoff error.
As shown in the following example: https://jsfiddle.net/xb813adh

The red bar is always 100px and scales accordingly.
The blue bar is 1px width scaled with a transform. It should always be the same width as the red bar.

When zooming in the width of the blue bar stays the same for 1, 1.10 and 1.25. 
After that it stays the same until a scale of 2.

Changing the example to scale 50px 2 times gives minor roundoff errors but is still incorrect.
Seen here: https://jsfiddle.net/y9jg10hp/

Other browsers show the correct working.

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