558893 - font-size-adjust produces inaccurate results at different font sizes

Status: RESOLVED DUPLICATE of bug 429605

(Core :: Graphics, defect)

Description

[Stanimir Stamenkov]

User-Agent:       Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.9.1.9) Gecko/20100317 SeaMonkey/2.0.4 (Spidey; Lightning 1.0b1; Mnenhy 0.8.0pre16)
Build Identifier: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.9.3a5pre) Gecko/20100412 Minefield/3.7a5pre

Following "Example V" from the current CSS Fonts Level 3 [1] draft:

http://www.w3.org/TR/2009/WD-css3-fonts-20090618/#relative-sizing-the-font-size-adjust-pro

I've extended the example to compare how the value I determine from aligning the big type box borders affects the normal size type.  I've determined font-size-adjust of 0.52 to match the aspect value of the "Arial" font family I've used in my example (see attached).


Reproducible: Always

Steps to Reproduce:
1. Open the attached example;
2. Observe the big type letter box borders are aligned vertically (have the same size);
3. Observe the normal type letter box borders.

Actual Results:  
The normal type letters have different sizes and their box borders do not align vertically.  The right (font-size-adjusted) letter appears smaller.


Expected Results:  
The normal type letters should have same size and their box borders should align vertically.


If one zooms the just the text (not full-zoom) one could notice how at different sizes the letters become of equal size.  At some sizes the right letter becomes larger than the left one, even.  The big type boxes also appear to misalign at different zoom levels.

FWIW, I'm observing the same with Firefox 3.6.3 and SeaMonkey 2.0.4, also.

[1] http://www.w3.org/TR/css3-fonts/

Comment 1

[Stanimir Stamenkov]

Attachment: Example demonstrating the problem

Comment 2

[Stanimir Stamenkov]

Attachment: Screenshot of the rendering I get

Comment 3

[John Daggett (:jtd)]

Guessing we're calculating the aspect ratio internally with scaled metrics but that's just a guess...

Comment 4

[Jonathan Kew [:jfkthame]]

This is the same issue as bug 429605, which was originally filed against Linux but actually applies to Windows as well (as noted in comments there).

Comment 5

[Stanimir Stamenkov]

FWIW, trying attachment 438570 [details] with SeaMonkey 1.1.19 (Gecko 1.8.1.24) the small type is o.k.  The big type is perfectly aligned using 'font-size-adjust: 0.521' (instead of 0.52) and the small type stays o.k.  This appears as regression on Windows, at least.