@Kovid: Hi Kovid, just a question.
I have a few EPUB3 files in my repository and on inspection I noticed that the function "Embed metadata" embedded, among other things, "calibre:user_metadata" in the according .OPF file. The embedded entries seems to be restricted to the by myself defined extra columns.
Spoiler:
<metadata>
[. . .]
<opf:meta property="calibre:user_metadata">{
"#subtitle": {
"#extra#": null,
"#value#": null,
"category_sort": "value",
"colnum": 6,
"column": "value",
"datatype": "text",
"display": {
"description": "Subtitle",
"use_decorations": false
},
"is_category": true,
"is_csp": false,
"is_custom": true,
"is_editable": true,
"is_multiple": null,
"is_multiple2": {},
"kind": "field",
"label": "subtitle",
"link_column": "value",
"name": "Subtitle",
"rec_index": 26,
"search_terms": [
"#subtitle"
],
"table": "custom_column_1"
}
}</opf:meta>
</metadata>
<manifest>
[. . .]
</manifest>
<spine>
[. . .]
</spine>
Can you tell me what the idea behind this is (or was) as I do not believe it will ever be used by my e-reader.