348908 - CSS line-height: in ems results in uneven line heights (rounding error)

Status: RESOLVED DUPLICATE of bug 442139

(Core :: Layout, defect)

Description

[Charles]

User-Agent:       Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.9a1) Gecko/20060816 Minefield/3.0a1
Build Identifier: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.9a1) Gecko/20060816 Minefield/3.0a1

When you use em units for CSS line-height, Gecko renderes uneven line heights. (FWIW, IE renders em-based line-height:s consistently.)

Because line heights within a paragraph differ by only 1 pixel, I suspect this is a rounding error -- Firefox is using cumulative rounding, when it should compute this value only once (and use it for every line) per paragraph.

Reproducible: Always

Steps to Reproduce:
1. Create a web page
2. Specify a line-height in em's




Expected Results:  
It's crucial that Firefox render line-height consistently. For people that care a lot about type, this means that line-height must be specified in pixels (rather than ems) to get a consistent line height.

Comment 1

[Ryan Flint [:rflint] (ping via IRC for reviews)]

*** Bug 348909 has been marked as a duplicate of this bug. ***