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Use a custom AttachableImageFormat type instead of directly relying on UTType. #1203

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Jul 8, 2025
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Use a custom AttachableImageFormat type instead of directly relying on UTType. #1203

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3 changes: 3 additions & 0 deletions Sources/Overlays/_Testing_CoreGraphics/Attachments/AttachableAsCGImage.swift
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Original file line number Diff line number Diff line change
Expand Up @@ -31,6 +31,7 @@ private import ImageIO
/// you have an image in another format that needs to be attached to a test,
/// first convert it to an instance of one of the types above.
@_spi(Experimental)
@available(_uttypesAPI, *)
public protocol AttachableAsCGImage {
/// An instance of `CGImage` representing this image.
///
Expand Down Expand Up @@ -73,6 +74,7 @@ public protocol AttachableAsCGImage {
func _makeCopyForAttachment() -> Self
}

@available(_uttypesAPI, *)
extension AttachableAsCGImage {
public var _attachmentOrientation: UInt32 {
CGImagePropertyOrientation.up.rawValue
Expand All @@ -83,6 +85,7 @@ extension AttachableAsCGImage {
}
}

@available(_uttypesAPI, *)
extension AttachableAsCGImage where Self: Sendable {
public func _makeCopyForAttachment() -> Self {
self
Expand Down
100 changes: 100 additions & 0 deletions Sources/Overlays/_Testing_CoreGraphics/Attachments/AttachableImageFormat+UTType.swift
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@@ -0,0 +1,100 @@
//
// This source file is part of the Swift.org open source project
//
// Copyright (c) 2024–2025 Apple Inc. and the Swift project authors
// Licensed under Apache License v2.0 with Runtime Library Exception
//
// See https://swift.org/LICENSE.txt for license information
// See https://swift.org/CONTRIBUTORS.txt for Swift project authors
//

#if SWT_TARGET_OS_APPLE && canImport(CoreGraphics)
@_spi(Experimental) public import Testing

public import UniformTypeIdentifiers

@available(_uttypesAPI, *)
extension AttachableImageFormat {
/// Get the content type to use when encoding the image, substituting a
/// concrete type for `UTType.image` in particular.
///
/// - Parameters:
/// - imageFormat: The image format to use, or `nil` if the developer did
/// not specify one.
/// - preferredName: The preferred name of the image for which a type is
/// needed.
///
/// - Returns: An instance of `UTType` referring to a concrete image type.
///
/// This function is not part of the public interface of the testing library.
static func computeContentType(for imageFormat: Self?, withPreferredName preferredName: String) -> UTType {
guard let imageFormat else {
// The developer didn't specify a type. Substitute the generic `.image`
// and solve for that instead.
return computeContentType(for: Self(.image, encodingQuality: 1.0), withPreferredName: preferredName)
}

switch imageFormat.kind {
case .png:
return .png
case .jpeg:
return .jpeg
case let .systemValue(contentType):
let contentType = contentType as! UTType
if contentType != .image {
// The developer explicitly specified a type.
return contentType
}

// The developer didn't specify a concrete type, so try to derive one from
// the preferred name's path extension.
let pathExtension = (preferredName as NSString).pathExtension
if !pathExtension.isEmpty,
let contentType = UTType(filenameExtension: pathExtension, conformingTo: .image),
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@grynspan grynspan Jul 7, 2025

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Note to self: on Windows, ImageCodecInfo::FilenameExtension should help us here. Windows does not have hierarchical type declarations (does it?)

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@grynspan grynspan Jul 7, 2025

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Pointer to a null-terminated string that contains all file-name extensions associated with the codec. The extensions are separated by semicolons.

contentType.isDeclared {
return contentType
}

// We couldn't derive a concrete type from the path extension, so pick
// between PNG and JPEG based on the encoding quality.
return imageFormat.encodingQuality < 1.0 ? .jpeg : .png
}
}

/// The content type corresponding to this image format.
///
/// The value of this property always conforms to [`UTType.image`](https://developer.apple.com/documentation/uniformtypeidentifiers/uttype-swift.struct/image).
public var contentType: UTType {
switch kind {
case .png:
return .png
case .jpeg:
return .jpeg
case let .systemValue(contentType):
return contentType as! UTType
}
}

/// Initialize an instance of this type with the given content type and
/// encoding quality.
///
/// - Parameters:
/// - contentType: The image format to use when encoding images.
/// - encodingQuality: The encoding quality to use when encoding images. For
/// the lowest supported quality, pass `0.0`. For the highest supported
/// quality, pass `1.0`.
///
/// If the target image format does not support variable-quality encoding,
/// the value of the `encodingQuality` argument is ignored.
///
/// If `imageFormat` is not `nil` and does not conform to [`UTType.image`](https://developer.apple.com/documentation/uniformtypeidentifiers/uttype-swift.struct/image),
/// the result is undefined.
public init(_ contentType: UTType, encodingQuality: Float = 1.0) {
precondition(
contentType.conforms(to: .image),
"An image cannot be attached as an instance of type '\(contentType.identifier)'. Use a type that conforms to 'public.image' instead."
)
self.init(kind: .systemValue(contentType), encodingQuality: encodingQuality)
}
}
#endif
36 changes: 8 additions & 28 deletions Sources/Overlays/_Testing_CoreGraphics/Attachments/Attachment+AttachableAsCGImage.swift
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Expand Up @@ -11,8 +11,6 @@
#if SWT_TARGET_OS_APPLE && canImport(CoreGraphics)
@_spi(Experimental) public import Testing

public import UniformTypeIdentifiers

@_spi(Experimental)
@available(_uttypesAPI, *)
extension Attachment {
Expand All @@ -24,10 +22,7 @@ extension Attachment {
/// - preferredName: The preferred name of the attachment when writing it
/// to a test report or to disk. If `nil`, the testing library attempts
/// to derive a reasonable filename for the attached value.
/// - contentType: The image format with which to encode `attachableValue`.
/// - encodingQuality: The encoding quality to use when encoding the image.
/// For the lowest supported quality, pass `0.0`. For the highest
/// supported quality, pass `1.0`.
/// - imageFormat: The image format with which to encode `attachableValue`.
/// - sourceLocation: The source location of the call to this initializer.
/// This value is used when recording issues associated with the
/// attachment.
Expand All @@ -39,26 +34,20 @@ extension Attachment {
/// - [`NSImage`](https://developer.apple.com/documentation/appkit/nsimage)
/// (macOS)
///
/// The testing library uses the image format specified by `contentType`. Pass
/// The testing library uses the image format specified by `imageFormat`. Pass
/// `nil` to let the testing library decide which image format to use. If you
/// pass `nil`, then the image format that the testing library uses depends on
/// the path extension you specify in `preferredName`, if any. If you do not
/// specify a path extension, or if the path extension you specify doesn't
/// correspond to an image format the operating system knows how to write, the
/// testing library selects an appropriate image format for you.
///
/// If the target image format does not support variable-quality encoding,
/// the value of the `encodingQuality` argument is ignored. If `contentType`
/// is not `nil` and does not conform to [`UTType.image`](https://developer.apple.com/documentation/uniformtypeidentifiers/uttype-swift.struct/image),
/// the result is undefined.
public init<T>(
_ attachableValue: T,
named preferredName: String? = nil,
as contentType: UTType? = nil,
encodingQuality: Float = 1.0,
as imageFormat: AttachableImageFormat? = nil,
sourceLocation: SourceLocation = #_sourceLocation
) where AttachableValue == _AttachableImageWrapper<T> {
let imageWrapper = _AttachableImageWrapper(image: attachableValue, encodingQuality: encodingQuality, contentType: contentType)
let imageWrapper = _AttachableImageWrapper(image: attachableValue, imageFormat: imageFormat)
self.init(imageWrapper, named: preferredName, sourceLocation: sourceLocation)
}

Expand All @@ -69,10 +58,7 @@ extension Attachment {
/// - preferredName: The preferred name of the attachment when writing it to
/// a test report or to disk. If `nil`, the testing library attempts to
/// derive a reasonable filename for the attached value.
/// - contentType: The image format with which to encode `attachableValue`.
/// - encodingQuality: The encoding quality to use when encoding the image.
/// For the lowest supported quality, pass `0.0`. For the highest
/// supported quality, pass `1.0`.
/// - imageFormat: The image format with which to encode `attachableValue`.
/// - sourceLocation: The source location of the call to this function.
///
/// This function creates a new instance of ``Attachment`` wrapping `image`
Expand All @@ -85,26 +71,20 @@ extension Attachment {
/// - [`NSImage`](https://developer.apple.com/documentation/appkit/nsimage)
/// (macOS)
///
/// The testing library uses the image format specified by `contentType`. Pass
/// The testing library uses the image format specified by `imageFormat`. Pass
/// `nil` to let the testing library decide which image format to use. If you
/// pass `nil`, then the image format that the testing library uses depends on
/// the path extension you specify in `preferredName`, if any. If you do not
/// specify a path extension, or if the path extension you specify doesn't
/// correspond to an image format the operating system knows how to write, the
/// testing library selects an appropriate image format for you.
///
/// If the target image format does not support variable-quality encoding,
/// the value of the `encodingQuality` argument is ignored. If `contentType`
/// is not `nil` and does not conform to [`UTType.image`](https://developer.apple.com/documentation/uniformtypeidentifiers/uttype-swift.struct/image),
/// the result is undefined.
public static func record<T>(
_ image: consuming T,
named preferredName: String? = nil,
as contentType: UTType? = nil,
encodingQuality: Float = 1.0,
as imageFormat: AttachableImageFormat? = nil,
sourceLocation: SourceLocation = #_sourceLocation
) where AttachableValue == _AttachableImageWrapper<T> {
let attachment = Self(image, named: preferredName, as: contentType, encodingQuality: encodingQuality, sourceLocation: sourceLocation)
let attachment = Self(image, named: preferredName, as: imageFormat, sourceLocation: sourceLocation)
Self.record(attachment, sourceLocation: sourceLocation)
}
}
Expand Down
56 changes: 10 additions & 46 deletions Sources/Overlays/_Testing_CoreGraphics/Attachments/_AttachableImageWrapper.swift
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Expand Up @@ -9,7 +9,7 @@
//

#if SWT_TARGET_OS_APPLE && canImport(CoreGraphics)
public import Testing
@_spi(Experimental) public import Testing
private import CoreGraphics

private import ImageIO
Expand Down Expand Up @@ -60,49 +60,12 @@ public struct _AttachableImageWrapper<Image>: Sendable where Image: AttachableAs
/// instances of this type it creates hold "safe" `NSImage` instances.
nonisolated(unsafe) var image: Image

/// The encoding quality to use when encoding the represented image.
var encodingQuality: Float
/// The image format to use when encoding the represented image.
var imageFormat: AttachableImageFormat?

/// Storage for ``contentType``.
private var _contentType: UTType?

/// The content type to use when encoding the image.
///
/// The testing library uses this property to determine which image format to
/// encode the associated image as when it is attached to a test.
///
/// If the value of this property does not conform to [`UTType.image`](https://developer.apple.com/documentation/uniformtypeidentifiers/uttype-swift.struct/image),
/// the result is undefined.
var contentType: UTType {
get {
_contentType ?? .image
}
set {
precondition(
newValue.conforms(to: .image),
"An image cannot be attached as an instance of type '\(newValue.identifier)'. Use a type that conforms to 'public.image' instead."
)
_contentType = newValue
}
}

/// The content type to use when encoding the image, substituting a concrete
/// type for `UTType.image`.
///
/// This property is not part of the public interface of the testing library.
var computedContentType: UTType {
if contentType == .image {
return encodingQuality < 1.0 ? .jpeg : .png
}
return contentType
}

init(image: Image, encodingQuality: Float, contentType: UTType?) {
init(image: Image, imageFormat: AttachableImageFormat?) {
self.image = image._makeCopyForAttachment()
self.encodingQuality = encodingQuality
if let contentType {
self.contentType = contentType
}
self.imageFormat = imageFormat
}
}

Expand All @@ -121,16 +84,16 @@ extension _AttachableImageWrapper: AttachableWrapper {
let attachableCGImage = try image.attachableCGImage

// Create the image destination.
let typeIdentifier = computedContentType.identifier as CFString
guard let dest = CGImageDestinationCreateWithData(data as CFMutableData, typeIdentifier, 1, nil) else {
let contentType = AttachableImageFormat.computeContentType(for: imageFormat, withPreferredName: attachment.preferredName)
guard let dest = CGImageDestinationCreateWithData(data as CFMutableData, contentType.identifier as CFString, 1, nil) else {
throw ImageAttachmentError.couldNotCreateImageDestination
}

// Configure the properties of the image conversion operation.
let orientation = image._attachmentOrientation
let scaleFactor = image._attachmentScaleFactor
let properties: [CFString: Any] = [
kCGImageDestinationLossyCompressionQuality: CGFloat(encodingQuality),
kCGImageDestinationLossyCompressionQuality: CGFloat(imageFormat?.encodingQuality ?? 1.0),
kCGImagePropertyOrientation: orientation,
kCGImagePropertyDPIWidth: 72.0 * scaleFactor,
kCGImagePropertyDPIHeight: 72.0 * scaleFactor,
Expand All @@ -151,7 +114,8 @@ extension _AttachableImageWrapper: AttachableWrapper {
}

public borrowing func preferredName(for attachment: borrowing Attachment<Self>, basedOn suggestedName: String) -> String {
(suggestedName as NSString).appendingPathExtension(for: computedContentType)
let contentType = AttachableImageFormat.computeContentType(for: imageFormat, withPreferredName: suggestedName)
return (suggestedName as NSString).appendingPathExtension(for: contentType)
}
}
#endif
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