Tcl

Add a Custom Header to a Related Item

Demonstrates the Chilkat Email.AddRelatedHeader method, which adds a custom MIME header field to an existing related item identified by its zero-based index. This example first adds a related style sheet (which becomes index 0) and captures its generated Content-ID, builds an HTML body that references the style sheet by that cid:, then attaches an extra header field to the related item and prints the resulting MIME.

Background: Like attachments, each related item (an inline image, style sheet, etc.) is a MIME part with its own small header block describing that part — Content-Type, Content-ID, Content-Location, and so on. AddRelatedHeader lets you insert additional fields into that per-part block, which is occasionally required for interoperability with clients that look for specific custom headers on embedded resources.

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Tcl


load ./chilkat.dll

#  Demonstrates the AddRelatedHeader method, which adds a custom MIME header field to an
#  existing related item, identified by its zero-based index.

set email [new_CkEmail]

CkEmail_put_Subject $email "Related item with a custom header"

#  Add a related item first (a style sheet); capture its generated Content-ID.  It becomes
#  related-item index 0.
set cid [CkEmail_addRelatedString $email "styles.css" "body { color: black; }" "utf-8"]
if {[CkEmail_get_LastMethodSuccess $email] == 0} then {
    puts [CkEmail_lastErrorText $email]
    delete_CkEmail $email
    exit
}

#  Build the HTML body, referencing the related style sheet by its Content-ID.  A
#  placeholder is used and then replaced with the actual Content-ID.
set sbHtml [new_CkStringBuilder]

CkStringBuilder_Append $sbHtml "<html><head><link rel=\"stylesheet\" href=\"cid:PLACEHOLDER_CID\"/></head><body>Styled content.</body></html>"
set numReplaced [CkStringBuilder_Replace $sbHtml "PLACEHOLDER_CID" $cid]
CkEmail_SetHtmlBody $email [CkStringBuilder_getAsString $sbHtml]

#  Add a custom header field to the first related item (index 0).
CkEmail_AddRelatedHeader $email 0 "X-Custom-Related-Header" "some value"

#  The custom header now appears in the related item's MIME part.
puts [CkEmail_getMime $email]

delete_CkEmail $email
delete_CkStringBuilder $sbHtml