- From: L. David Baron <dbaron@dbaron.org>
- Date: Sun, 17 Oct 2010 12:46:55 -0700
- To: public-css-testsuite@w3.org
- Cc: Arron Eicholz <Arron.Eicholz@microsoft.com>
These tests: http://test.csswg.org/suites/css2.1/20101001/html4/vertical-align-115.htm http://test.csswg.org/suites/css2.1/20101001/html4/vertical-align-116.htm http://test.csswg.org/suites/css2.1/20101001/xhtml1/vertical-align-115.xht http://test.csswg.org/suites/css2.1/20101001/xhtml1/vertical-align-116.xht are testing for particular alignment of subscripts and superscripts whose origin I don't understand; it's not the values in the font metrics. Gecko implements subscript and superscript alignment using the metrics of the font, which I think should at least be the preferred way, although it's not required by the spec. The Ahem font has a subscript Y offset in its OS2 table of 143 (on a 1000 grid) and a superscript Y offset of 453. This means that for 48px Ahem, the subscript should have its baseline lowered 6.86px and a superscript should have its baseline raised 21.74px. Since the baseline of Ahem is 1/5 from the bottom (i.e., 9.6px in 48px, 19.2px in 96px, and 28.8px in 144px), in the superscript testcase the subscript glyph should have its bottom 16.46px below the line's baseline (9.6px + 6.86px); in the superscript testcase the superscript glyph should have its bottom 12.14px above the normal baseline (21.74 - 9.6). In contrast, the 96px glyph (in test 115) should extend 19.2px below the baseline and the 144px glyph (in test 116) should extend 28.8px below the baseline. This would mean that the values of 'top' to be used in the tests, if a browser used the font's metrics, and ignoring all the potential rounding issues from these horribly unround numbers, would be 45.26px (48px - (19.2px - 16.46px)) for test 115 and 55.06px (96px - (28.8px + 12.14px) for test 116. In fact, Mozilla on Linux passes the tests if I adjust the 44px to 45px and the 0.6in (57.6px) to 55px. That said, I think these tests should be removed, since the spec has no requirement for using the font's metrics for subscript and superscript offsets. -David -- L. David Baron http://dbaron.org/ Mozilla Corporation http://www.mozilla.com/
Received on Sunday, 17 October 2010 19:47:25 UTC