apple: a boxed HtmlConfig property cannot be set from Swift without a hand-written type encoding

[andiwand]

HtmlConfig.spreadsheetLimit is a TableDimensions boxed in an NSValue. Swift has no @encode, so a caller has to spell the encoding out:

config.spreadsheetLimit = withUnsafeBytes(of: TableDimensions(rows: 100_000, columns: 500)) {
    NSValue(bytes: $0.baseAddress!, objCType: "{ODRTableDimensions=II}")
}

That literal is what opendocument-app/OpenDocument.ios#185 now carries, and it is a second source of truth for the struct's layout sitting in a consumer. A field added to ODRTableDimensions breaks it silently: getValue:size: checks the size, not the encoding.

Style+Optionals.swift already solves the read half — "the ObjC layer boxes an absent std::optional as nil in an NSNumber or NSValue, which is faithful but not how Swift reads" — and its header says this is what the target exists for. There is no write half, because HtmlConfig is the only place a boxed property is settable.

Suggestion

An apple/swift/Html+Optionals.swift beside it, naming as that file does (fontColor → color):

extension HtmlConfig {
  public var sheetLimit: TableDimensions? { get set }
  public var zoom: Double? { get set }
  // ...
}

Alternatively drop the boxing on this one property and give ODRHtmlConfig a setSpreadsheetLimit: taking the struct plus a clearSpreadsheetLimit. Less uniform, no new file.

The whole surface

property	boxed as	from Swift today
spreadsheetLimit	NSValue / ODRTableDimensions	only with the encoding literal
spreadsheetViewportMode	NSNumber / enum	NSNumber(value: mode.rawValue)
spreadsheetCellLimit, viewportWidth, initialZoom, pageRangeEnd	NSNumber	NSNumber(value:)

Only the first is actually blocked; the rest are merely not how Swift reads.

Nothing under apple/tests or apple/swift sets any of them, so the write path has no coverage either.

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