CGContext renders text upside down - ios

Question

I am rendering a NSAttributedString with CGContext, however when it renders the text is upside down :(
This is what I came up with:
override func draw(with box: PDFDisplayBox, in context: CGContext) {
UIGraphicsPushContext(context)
context.saveGState()
let paragraphStyle = NSMutableParagraphStyle()
paragraphStyle.alignment = .center
let attributes = [
NSAttributedString.Key.paragraphStyle: paragraphStyle,
NSAttributedString.Key.font: UIFont.systemFont(ofSize: 80.0),
NSAttributedString.Key.foregroundColor: UIColor.red
]
NSAttributedString(string: self.widgetStringValue!, attributes: attributes).draw(in: self.bounds)
context.restoreGState()
UIGraphicsPopContext()
}
I have tried adding this:
context.translateBy(x: 0.0, y: bounds.height)
context.scaleBy(x: 1.0, y: -1.0)
But then the text does not appear on my screen at all :(
What am I doing wrong?
UPDATE
As requested here is my full TextAnnotation class:
class TextAnnotation: PDFAnnotation {
var currentText: String?
override init(bounds: CGRect, forType annotationType: PDFAnnotationSubtype, withProperties properties: [AnyHashable : Any]?) {
super.init(bounds: bounds, forType: annotationType, withProperties: properties)
self.widgetFieldType = PDFAnnotationWidgetSubtype(rawValue: PDFAnnotationWidgetSubtype.text.rawValue)
self.font = UIFont.systemFont(ofSize: 80)
self.isMultiline = true
self.widgetStringValue = "Text Here"
self.currentText = self.widgetStringValue!
}
override func draw(with box: PDFDisplayBox, in context: CGContext) {
UIGraphicsPushContext(context)
context.saveGState()
let pageBounds = bounds
context.translateBy(x: 0, y: pageBounds.height)
context.scaleBy(x: 1, y: -1)
let paragraphStyle = NSMutableParagraphStyle()
paragraphStyle.alignment = .center
let attributes: [NSAttributedString.Key: Any] = [
.paragraphStyle: paragraphStyle,
.font: UIFont.systemFont(ofSize: 80),
.foregroundColor: UIColor.red
]
widgetStringValue!.draw(in: pageBounds, withAttributes: attributes)
context.restoreGState()
UIGraphicsPopContext()
}
required init?(coder aDecoder: NSCoder) {
fatalError("init(coder:) has not been implemented")
}
}

Answer 1

In my case, I was subclassing a PDFAnnotation. The key was using the correct y-value (which was a pain to figure out) for the translateBy call in my draw method:
override func draw(with box: PDFDisplayBox, in context: CGContext) {
let text = NSString(string: "Hello!")
UIGraphicsPushContext(context)
context.saveGState()
context.translateBy(x: 0, y: bounds.height + (2 * bounds.minY))
context.scaleBy(x: 1, y: -1.0)
text.draw(in: bounds.offsetBy(dx: 2, dy: 0), withAttributes: attributes)
context.restoreGState()
UIGraphicsPopContext()
}

Answer 2

In a PDFAnnotation, you should just add the translateBy(x:y:) and scaledBy(x:y:) as you’ve discussed:
override func draw(with box: PDFDisplayBox, in context: CGContext) {
UIGraphicsPushContext(context)
context.saveGState()
context.translateBy(x: 0, y: bounds.height)
context.scaleBy(x: 1, y: -1)
let paragraphStyle = NSMutableParagraphStyle()
paragraphStyle.alignment = .center
let attributes: [NSAttributedString.Key: Any] = [
.paragraphStyle: paragraphStyle,
.font: UIFont.systemFont(ofSize: 80),
.foregroundColor: UIColor.red
]
widgetStringValue?.draw(in: bounds, withAttributes: attributes)
context.restoreGState()
UIGraphicsPopContext()
}
In a PDFPage you should use bounds(for:) to get the bounds within that PDFDisplayBox, and then use translateBy(x:y:) and scaledBy(x:y:) as you’ve discussed:
override func draw(with box: PDFDisplayBox, to context: CGContext) {
UIGraphicsPushContext(context)
context.saveGState()
let pageBounds = bounds(for: box)
context.translateBy(x: 0, y: pageBounds.height)
context.scaleBy(x: 1, y: -1)
let paragraphStyle = NSMutableParagraphStyle()
paragraphStyle.alignment = .center
let attributes: [NSAttributedString.Key: Any] = [
.paragraphStyle: paragraphStyle,
.font: UIFont.systemFont(ofSize: 80),
.foregroundColor: UIColor.red
]
text.draw(in: pageBounds, withAttributes: attributes)
context.restoreGState()
UIGraphicsPopContext()
}