Intent to ship: vertical text support (CSS writing-mode and related properties)

Jonathan Kew jfkthame at
Wed Jul 1 10:09:06 UTC 2015

Following up on the message quoted below (Intent to ship on pre-release 
channels), we are now planning to ship support for CSS writing-mode, 
text-orientation, and related logical-direction properties (things like 
block-size and inline-size, margin-block-start, etc) enabled by default 
on all channels.

The RELEASE_BUILD condition that has been keeping these features 
disabled for release builds was removed in bug 1138384, which landed for 
Gecko 41. So unless we have reason to revert this during the Aurora/Beta 
period, we expect these features to ship in Firefox 41.

Relevant specifications:


On 2/3/15 12:59, Jonathan Kew wrote:
> See [1] for additional background on this feature.
> We are aiming to enable support for CSS writing-mode and related
> features (i.e. vertical text support) in Gecko 39.[2]
> This will be enabled behind an #ifndef RELEASE_BUILD condition, so that
> for the time being, these features will be available by default in
> developer builds, but not in the release version.
> Once more key parts of CSS layout have been adapted to support vertical
> mode, we'll remove the condition and enable writing-mode by default on
> release as well as dev channels.[3]
> cc'ing firefox-dev and dev-gaia lists, particularly to make people aware
> that while we encourage experimentation with the new properties (please
> test and file bugs!), you should not attempt to use them in front-end
> code that will ship to release channels where writing-mode remains
> disabled-by-default for now.
> JK
> [1]
> [2]
> [3]

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