[mpeg-OTspec] cmap format4 structure question

Levantovsky, Vladimir vladimir.levantovsky at monotype.com
Tue Mar 18 22:56:19 CET 2014


Please review the text changes proposed by Bob. We did discuss the need to make changes in the ‘cmap’ format 4 spec (https://groups.yahoo.com/neo/groups/mpeg-OTspec/conversations/topics/1107) to make sure it matches with the expected behavior of the existing implementations but have not [until now] discussed the proposed new spec language (see below).

If I don’t receive any objection by the end of this week I will incorporate the language Bob Hallissy proposed as AHG consensus opinion.

Thank you,

From: mpeg-OTspec at yahoogroups.com [mailto:mpeg-OTspec at yahoogroups.com] On Behalf Of Bob Hallissy
Sent: Wednesday, March 12, 2014 5:43 PM
To: OTspec
Subject: Re: [mpeg-OTspec] cmap format4 structure question

On 2014-01-24 8:41 AM, Opstad, Dave wrote:
As I recall, the TrueType code for format 4 'cmap' subtables is looking for a sentinel of (0xFFFF, 0xFFFF) specifically, so I don't think the (0xFFFC, 0xFFFF) you posit would work.
Dave Opstad

If this is the case, should the OFF spec be tightened up to reflect this? Specifically, should section Format 4: Segment mapping to delta values be revised:

For the search to terminate, the final endCode value must be 0xFFFF.
For the search to terminate, the final startCode and endCode values must be 0xFFFF.

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