Bug 17582 – font size specified in % is rounded down making text not readable

• Status: NEW
• Component: CSS

[jasneet]

I Steps:
Go to
http://suggestions.yahoo.com/

II Issue:
The text in footer is not readable.

III Conclusion: font size specified in % is causing the issue. There is a significant rendering different between FF and webkit with font 80% and 77%. webkit renders small text when the size is 77%.Therefore WebKit is choosing to round down where as other browsers choose to round up (when choosing the "intrinsic font" to scale to 77%).

IV Other browsers: 
FF: ok
Opera: ok
IE 7: ok

V Nightly tested: 30236

[jasneet]

Created attachment 19419 [details]
screenshot

[jasneet]

Created attachment 19420 [details]
reduction

[Nicholas Shanks]

Possible cause is Firefox on Windows supporting font-size-adjust? The fonts in your reduction are Arial and Verdana. the latter has a much larger x-height than the former, possibly causing the Arial text size to be scaled up to compensate.
Another possible cause is Firefox not supporting fractional point sizes whereas we do?

16px * 0.77 = 12.32px  (i.e. 77% of 12pt is 9.24pt)
16px * 0.80 = 12.80px  (i.e. 80% of 12pt is 9.6pt)

If rounding upwards, both 80% and 77% would be rounded to the same size (10pt) whereas Safari would draw at 9.24pt and 9.6pt.

[Shane Stephens]

Looking at the reduction (Mac OSX, Chrome Canary), the 77% case is almost half-way between the 65% and 80% cases, whereas it should be much closer to the 80% case if we were doing linear scaling and using fractional font sizes.