423601 - Inconsistent positioning of <msub> when zooming

Status: RESOLVED WORKSFORME

(Core :: MathML, defect)

Description

[Jesse Ruderman]

Attachment: testcase

Steps to reproduce:
1. Load the testcase
2. Zoom out a few times with Cmd+-

Result: At some zoom levels, the '2' is all the way below the 'x'.  At other zoom levels, it is only slightly below the 'x'.

Expected: Consistent appearance.

I can't reproduce this by changing the font-size using CSS; I can only reproduce it by zooming.

The testcase is a copy of layout/reftests/bugs/345563-sub.xhtml.

Comment 1

[Karl Tomlinson (:karlt)]

Hmm.  What I see (on Linux, with STIX fonts) seems to be just a result of glyph hinting effectively rounding the height of the glyphs to integer pixels (which is therefore only noticeable when zooming out).

Are you seeing more than a 1 or 2 pixel difference?

Comment 2

[Jesse Ruderman]

Yes, much more than 1 or 2 pixels.  Normally, the bottom of the '2' is slightly below the bottom of the 'x'.  But at certain zoom-out levels, the *top* of the '2' is below the bottom of the 'x'.

Comment 3

[Karl Tomlinson (:karlt)]

This is quite significant.

It is noticeable at smaller sizes in the + between k and 1 in number 4 of http://www.mozilla.org/projects/mathml/demo/texvsmml.xhtml
(The + ends up well below the k and 1.)

And also the hat accents above x + xy + xyz move down over the base chars at some (more noticeably smaller) sizes here
http://www.mozilla.org/projects/mathml/start.xhtml

One thing consistent about the ^ and + characters and the <msub> is that verical positioning depends on tight glyph bounds, but the problem only happens on Mac.

Comment 4

[Jesse Ruderman]

Still happens on trunk (Mac).

Comment 5

[Jesse Ruderman]

WFM on trunk (Mac OS X 10.5).