NSView drawing explained - macos

Question

I am trying to create a object that can be dragged and rotated in an NSView and have been successful in doing so using NSBezierPath. I am creating multiple objects and storing them in a class and using NSBezierPath.transform(using: AffineTransform) to modify the path in response to drag and rotation inputs.
This all works fine but I now want to add text to the shape and it seems there are a different set of rules for dealing with text.
I have tried using Core Text by creating a CTFrame but have no idea how to move or rotate this.
Is there a good reason for why the handling of text is so different from NSBezierPath.
And then there is the difference between AffineTransform and CGAffineTransform. The whole thing is pretty confusing and good documentation explaining the difference seems hard to come by.
Below is the code for creating and moving the shape which seems work perfectly. I have no idea how to move the text, ideally without having to recreate it. Is there any way to translate and rotate the CTFrame?
var path: NSBezierPath
var location: NSPoint {
didSet {
// move()
}
}
var angle: CGFloat {
didSet {
let dx = angle - oldValue
rotate(dx)
}
}
func createPath(){
// Create a simple path with a rectangle
self.path = NSBezierPath(rect: NSRect(x: -1*width/2.0, y: -1*height/2.0, width: width, height: height))
let line = NSBezierPath()
line.move(to: NSPoint(x: width/2.0, y:0))
line.line(to: NSPoint(x: width/2.0+leader, y:0))
self.path.append(line)
// Label !!
let rect = NSRect(x: width/2.0, y: 0, width: leader, height: height/2.0)
let attrString = NSAttributedString(string: assortmentLabel, attributes: attributesForLeftText)
self.labelFrame = textFrame(attrString: attrString, rect: rect)
// ??? How to rotate the CTFrame - is this even possible
move()
rotate(angle)
}
func rotate(_ da: CGFloat){
// Move to origin
let loc = AffineTransform(translationByX: -location.x, byY: -location.y)
self.path.transform(using: loc)
let rotation = AffineTransform(rotationByDegrees: da)
self.path.transform(using: rotation)
// Move back
self.path.transform(using: AffineTransform(translationByX: location.x, byY: location.y))
}
func move(){
let loc = AffineTransform(translationByX: location.x, byY: location.y)
self.path.transform(using: loc)
}
func draw(){
guard let context = NSGraphicsContext.current?.cgContext else {
return
}
color.set()
path.stroke()
if isSelected {
path.fill()
}
if let frame = self.labelFrame {
CTFrameDraw(frame, context)
}
}
// -----------------------------------
// Modify the item location
// -----------------------------------
func offsetLocationBy(x: CGFloat, y:CGFloat)
{
location.x=location.x+x
location.y=location.y+y
let loc = AffineTransform(translationByX: x, byY: y)
self.path.transform(using: loc)
}
EDIT:
I have changed things around a bit to now draw the shape at origin 0,0 and to then apply the transformation to CGContext prior to drawing the shape.
This does the job and using CTDrawFrame now works correctly...
Well almost...
On my test app it works perfectly but when I integrated the exact same code to the production app the text appears upside-down and all characters shown on top of each other.
As far as I can tell there is nothing different about the views the drawing is taking place in - uses the same NSView subclass.
Is there something else that could upset the drawing of the text - seems like an isFlipped issue but why would this happen in the one app and not the other.
Everything else seems to draw correctly. Tearing my hair out on this.

Answer 1

After much struggling it seems I got lucky with the test app working at all and needed to set the textMatrix on BOTH apps to ensure things work properly under all conditions.
It also seems one can't create the CTFrame and later just scale it and redraw it - well it didn't work for me so I had to recreate it in the draw() method each time!