Images being flipped when adding to NSAttributedString - swift

Question

I have a strange problem when resizing an image that's in a NSAttributedString. The resizing extension is working fine, but when the image is added to the NSAttributedString, it gets flipped vertically for some reason.
This is the resizing extension:
extension NSImage {
func resize(containerWidth: CGFloat) -> NSImage {
var scale : CGFloat = 1.0
let currentWidth = self.size.width
let currentHeight = self.size.height
if currentWidth > containerWidth {
scale = (containerWidth * 0.9) / currentWidth
}
let newWidth = currentWidth * scale
let newHeight = currentHeight * scale
self.size = NSSize(width: newWidth, height: newHeight)
return self
}
}
And here is the enumeration over the images in the attributed string:
newAttributedString.enumerateAttribute(NSAttributedStringKey.attachment, in: NSMakeRange(0, newAttributedString.length), options: []) { value, range, stop in
if let attachement = value as? NSTextAttachment {
let image = attachement.image(forBounds: attachement.bounds, textContainer: NSTextContainer(), characterIndex: range.location)!
let newImage = image.resize(containerWidth: markdown.bounds.width)
let newAttribute = NSTextAttachment()
newAttribute.image = newImage
newAttributedString.addAttribute(NSAttributedStringKey.attachment, value: newAttribute, range: range)
}
}
I've set breakpoints and inspected the images, and they are all in the correct rotation, except when it reaches this line:
newAttributedString.addAttribute(NSAttributedStringKey.attachment, value: newAttribute, range: range)
where the image gets flipped vertically.
I have no clue what could be causing this vertical flip. Is there a way to fix this?

Answer 1

If you look at the developer docs for NSTextAttachment:
https://developer.apple.com/documentation/uikit/nstextattachment
The bounds parameter is defined as follows:
“Defines the layout bounds of the receiver's graphical representation in the text coordinate system.”
I know that when using CoreText to layout text, you need to flip the coordinates, so I should imagine you need to transform your bounds parameter with a vertical reflection too.
Hope that helps.

Answer 2

I figured it out and it was so much simpler than I was making it.
Because the image was in a NSAttribuetdString being appended into a NSTextView I didn't need to resize each image in the NSAttributedString, rather I just had to set the attachment scaling inside the NSTextView with
markdown.layoutManager?.defaultAttachmentScaling = NSImageScaling.scaleProportionallyDown
One line is all it took