Bug 297455 – CSS dominant-baseline property should be inherited per SVG2 / CSS Inline 3

• Component: SVG
• Status: NEW

[Stephen Thomas]

If a <text> element is given a y-position and the dominant baseline is set to middle, the y-attribute value is used to place the bottom of the text rather than its middle.

Reproduction: https://codepen.io/sathomas/pen/EaVowqb

[Radar WebKit Bug Importer]

<rdar://problem/158944151>

[Karl Dubost]

all the tests in SVG mentioning dominant-baseline are passing.
https://wpt.fyi/results/svg?label=master&label=experimental&aligned&q=dominant-baseline


But this is working.
<text x="50" y="100" dominant-baseline="middle">Hello</text>

So the issue is elsewhere.

in SVG2
https://w3c.github.io/svgwg/svg2-draft/text.html#DominantBaselineProperty

==========
This property is defined in the CSS Line Layout Module 3 specification. See 'dominant-baseline'. [css-inline-3]

SVG 2 introduces some changes to the definition of this property. In particular:

* The 'reset-size' value is no longer supported. Any change in font-size resets the dominant baseline table.
* The 'use-script' and 'no-change' values are no longer supported.
* The property is now inherited. (Behavior is effectively unchanged.)

SVG uses the value of the dominant-baseline property to align glyphs relative to the ‘x’ and ‘y’ attributes. For the text-orientation value sideways, the auto value for dominant-baseline is alphabetic; however, for backwards compatibility, the glyphs should be aligned to the ‘x’ and ‘y’ attributes using the value central.
====

The issue is that tspan is not inheriting from text. That's the issue, but the spec says it should.

[Karl Dubost]

I also open Bug 311552
remove use-script, no-change, reset-size from dominant-baseline per spec

[Karl Dubost]

Fixing this test, create a regression that needs to be addressed first which has a kind of baseline baked-in for get*PositionOfChar

--- /Users/karlcow/code/OpenSource/WebKitBuild/Debug/layout-test-results/imported/w3c/web-platform-tests/svg/text/scripted/getstartpositionofchar-dominant-baseline-expected.txt
+++ /Users/karlcow/code/OpenSource/WebKitBuild/Debug/layout-test-results/imported/w3c/web-platform-tests/svg/text/scripted/getstartpositionofchar-dominant-baseline-actual.txt
@@ -1,6 +1,6 @@
 Test Test
 Test Test
 
-PASS textPath: get*PositionOfChar().y should not depend on dominant-baseline
-PASS tspan: get*PositionOfChar().y should not depend on dominant-baseline
+FAIL textPath: get*PositionOfChar().y should not depend on dominant-baseline assert_equals: expected 95.556640625 but got 80
+FAIL tspan: get*PositionOfChar().y should not depend on dominant-baseline assert_equals: expected 115.556640625 but got 100
 
I need to fix it first. in Bug 311553

[Karl Dubost]

Pull request: https://github.com/WebKit/WebKit/pull/62107

[Karl Dubost]

This PR needs to be merged first https://github.com/WebKit/WebKit/pull/62106

[Karl Dubost]

Created attachment 478934 [details]
testcase

The testcase 7 illustrates the issue.

[Karl Dubost]

*** Bug 139258 has been marked as a duplicate of this bug. ***