[Webkit-unassigned] [Bug 208824] New: -webkit-text-orientation Behavior Doesn't Match the Spec

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=208824

            Bug ID: 208824
           Summary: -webkit-text-orientation Behavior Doesn't Match the
                    Spec
           Product: WebKit
           Version: WebKit Local Build
          Hardware: All
                OS: All
            Status: NEW
          Severity: Normal
          Priority: P2
         Component: CSS
          Assignee: webkit-unassigned at lists.webkit.org
          Reporter: guowei_yang at apple.com

Created attachment 393055

  --> https://bugs.webkit.org/attachment.cgi?id=393055&action=review

Comparison between the correct text baseline alignment and incorrect baseline alignment

Webkit has the -webkit-text-orientation property, and ideally we want to have it match the spec mentioned in  https://drafts.csswg.org/css-writing-modes/#text-orientation and https://drafts.csswg.org/css-writing-modes/#text-baselines
Currently, the problem for -webkit-text-orientation is in the text baseline selection. According to the spec related to text baselines, "In vertical typographic mode, the central baseline is used as the dominant baseline when text-orientation is mixed or upright. Otherwise the alphabetic baseline is used." However in the case of Webkit, alphabetic baseline is used in both sideways and mixed, which is incorrect. 

One example is shown below: 

<style>
  div > div {
  font-size: 200%;
}
</style>
<div style="writing-mode: vertical-lr; -webkit-text-orientation: mixed">
  before
  <div style="display: inline-block; background: lime; height: 100px; width: 100px;">foobar</div>
  after
</div>

Current WebKit renders the text in a fashion shown in the attached image on the left, which is aligned on their alphabetic baseline, whereas according to the spec, they should be aligned using the ideographic baseline because we are in vertical writing mode and text orientation is mixed. The correct result is shown on the right.

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