Hi everyone,

in the context of the new text anchor layouting infrastructure there is still one thing missing. Currently start of header is not included in Character class>>#separators. This leads to problems with text editing Morphs. As start of header is not printed at all (not even as white space) I would rather classify it as a separator and add it to the list in Character class>>#separators and to Character>>#isSeparator. The advantage of this approach is that we would not need any special case in the text editing morphs. The disadvantage is that the list of separators will be less obvious to understand.

Any thoughts about this? 

Bests
Patrick

P.S.: Conceptually start of header (or heading) is a control character. ietf says: " A communication control character used at the beginning of a sequence of characters which constitute a machine-sensible address or routing information.  Such a sequence is referred to as the "heading."  An STX character has the effect of terminating a heading."
(https://tools.ietf.org/html/rfc20#section-5.2)

>Patrick Rein uploaded a new version of Collections to project The Trunk:
>http://source.squeak.org/trunk/Collections-pre.857.mcz
>
>==================== Summary ====================
>
>Name: Collections-pre.857
>Author: pre
>Time: 4 October 2019, 11:04:30.363303 am
>UUID: 5ef00b65-3884-c445-b276-0cc01f0b10a1
>Ancestors: Collections-pre.856
>
>Adds startOfHeader to Character, adds empty abstract implementations of scanFrom:, writeScanOn: to TextAttribute to allow for Texts which include TextAttributes which do not implement serialization to still be serialized, adds a comment to these methods.
>
>=============== Diff against Collections-pre.856 ===============
>
>Item was added:
>+ ----- Method: Character class>>startOfHeader (in category 'accessing untypeable characters') -----
>+ startOfHeader
>+ 
>+ 	^ self value: 1 !
>
>Item was added:
>+ ----- Method: TextAttribute class>>scanFrom: (in category 'fileIn/Out') -----
>+ scanFrom: strm
>+ 	"Read the text attribute properties from the stream. When this method has
>+ 	been called the concrete TextAttribute class has already been selected via
>+ 	scanCharacter. (see TextAttribute class>>#newFrom:).
>+ 	For writing the format see TextAttribute>>#writeScanOn:"!
>
>Item was added:
>+ ----- Method: TextAttribute>>writeScanOn: (in category 'fileIn/fileOut') -----
>+ writeScanOn: strm
>+ 	"Implement this method for a text attribute to define how it it should be written
>+ 	to a serialized form of a text object. The form should correspond to the source
>+ 	file format, i.e. use a scan character to denote its subclass.
>+ 	As TextAttributes are stored in RunArrays, this method is mostly called from RunArray>>#write scan.
>+ 	For reading the written information see TextAttribute class>>#scanFrom:"
>+ 	
>+ 	"Do nothing because of abstract class"!
>
>