807988 - transform scale text letter spacing incorrect and hardware dependent

Status: UNCONFIRMED

(Core :: Layout: Text and Fonts, defect)

Description

[Ryan Slominski]

Attachment: HTML file which demonstrates the issue; try on Firefox 16 and compare with IE 9

Scaling text using CSS transform scale does not maintain the letter spacing between characters at the same proportion as the original un-scaled text.  This phenomenon is generally more evident with smaller initial font sizes, but varies based also by font family and platform - If I look at the attached example HTML file on my work computer vs home computer I get different results even though they are both Windows 7 64-bit with Firefox 16.2.  In both cases the letter spacing is incorrect, just different, suggesting that perhaps graphics hardware is being used to determine rendering accuracy (home computer has gaming graphics card).  Contrast this with IE 9, which maintains perfect letter spacing on both machines.  Oddly a starting font size of 3px looks decent, whereas a starting font size of 10px has obvious issues with characters bumping into each other.

Comment 1

[Ryan Slominski]

I've now tried the attached testcase with Firefox on a Linux machine and a Mac and can confirm that the problem appears much less severe compared to on Windows, but is still present.

Comment 2

[Ryan Slominski]

Attachment: Testcase Screenshot from Windows 7 64-bit from machine with gaming graphics card

Comment 3

[Ryan Slominski]

Attachment: Testcase Screenshot from Windows 7 64-bit with onboard graphics

Comment 4

[Ryan Slominski]

Attachment: Testcase Screenshot from IE9