GB225 20.20.02.2 Format alignment specifiers vs. text direction LWG 3327

[wg21bot]

std::format() alignment specifiers should be independent of text direction
The align specifiers for formatting standard integer and string types are expressed in terms of "left" and "right". However, "left alignment" as currently defined in the format() specification might end up being right-aligned when the resulting string is displayed in a RTL or bidirectional locale.
This ambiguity can be resolved by removing "left" and "right" and replacing with "start" and "end", without changing any existing implementation and without changing the intent of the feature.

Proposed change:
In [tab:format.align]:
Forces the field to be left-aligned within aligned to the start of the available space
and
Forces the field to be right-aligned within aligned to the end of the available space

[tahonermann]

SG16 plans to discuss this comment Tuesday morning:

• http://wiki.edg.com/bin/view/Wg21belfast/SG16

[JeffGarland]

Reviewed Monday in LWG small group.

[tahonermann]

SG16 in Belfast: recommend to accept.

Rationale: The proposed wording describes current implementation behavior and the desired behavior for right-to-left (RTL) text. For an implementation to conform to the current wording and actually align RTL text in the directions indicated, std::format would be required to insert directional isolate code points around inserted text in order to force binding of padding in one direction or another. The proposed wording avoids the need for any such heroics while allowing programmers to encode such isolates themselves as desired when authoring format strings.

Removing the SG16 label. This is ready for LWG.

SG16 minutes are available at:

• http://wiki.edg.com/bin/view/Wg21belfast/SG16NBGB225

[JeffGarland]

LWG large group wed. Will write and LWG issue to update the wording.

[Dani-Hub]

The associated issue is LWG 3327

[mclow]

Friday AM in LWG - accept.

[jensmaurer]

Accepted.