topics flex initial value

initial values of flex

Spec_tags     : css3-flexbox
Owner_tags    : fantasai #Who's driving the discussion?
Status_tags   : Closed #[ Open | Closed | Pending ] [, Urgent]?
Added_dt      : 2012-05-30 #Date added as WG discussion request
Action        : Discuss and resolve.
Issue_urls    : http://lists.w3.org/Archives/Public/www-style/2012May/0753.html
Proposal_urls : http://lists.w3.org/Archives/Public/www-style/2012May/1177.html
Agenda_urls   :  #If this is part of an ordered series of related topics, e.g. LC issues, use this to link to the supertopic agenda

Background

There's been a lot of discussion lately (after the Hamburg F2F) on what the initial values of 'flex' should be, and there are some concerns raised by Ojan with the resolution recorded there.

Problem Statement

What are the best initial values for flex?

Proposal(s)

Proposal A: flex: none

• Pros
  • It's easier to use alignment and auto margins
  • Easier for use cases that want some but not most items flexible, e.g. one item takes up all free space
• Cons
  • Doesn't have negative flexibility be default, which could help prevent overflow in many cases
  • Inconsistent with 'stretch' default in cross-dimension

Proposal B: flex: auto

• Pros
  • Negative flex is on by default, preventing overflow in many cases
  • Consistent with 'stretch' default in cross-dimension
• Cons
  • Harder to use alignment and margins, since have to turn off flex first
  • More work for use cases that want most items inflexible

Proposal C: flex: 0 1 auto

• Pros
  • Negative flex is on by default, preventing overflow in many cases
  • Easy to use alignment and auto margins since positive free space is not flexed
  • Easy for use cases where free space is distributed to e.g. only one item
• Cons
  • Inconsistent with 'stretch' default in cross-dimension

Resolution

The WG resolved on Proposal C.