How to Change NSTextField Font Size When Used in SwiftUI - swiftui

Question

Below is a demo app with a simple NSTextField in a Mac app. For some reason, the font size won't change no matter what I try.
import Cocoa
import SwiftUI
#main
struct SwiftUIWindowTestApp: App {
var body: some Scene {
WindowGroup {
ContentView()
}
}
}
struct ContentView: View {
#State private var text = "Text goes here..."
var body: some View {
FancyTextField(text: $text)
.padding(50)
}
}
struct FancyTextField: NSViewRepresentable {
#Binding var text: String
func makeNSView(context: Context) -> NSTextField {
let textField = NSTextField()
textField.font = NSFont.systemFont(ofSize: 30) //<- Not working
return textField
}
func updateNSView(_ nsView: NSTextField, context: Context) {
nsView.stringValue = text
}
}
That's the whole app. I'm not doing anything else in this simple example. I can change the text color and other attributes, but for some reason the font size doesn't change.
On a whim, I tried changing it on the SwiftUI side as well, but I didn't expect that to work (and it doesn't):
FancyTextField(text: $text)
.font(.system(size: 20))
Any ideas?

Answer 1

This is a particularly weird one:
struct FancyTextField: NSViewRepresentable {
#Binding var text: String
func makeNSView(context: Context) -> NSTextField {
let textField = MyNSTextField()
textField.customSetFont(font: .systemFont(ofSize: 50))
return textField
}
func updateNSView(_ nsView: NSTextField, context: Context) {
nsView.stringValue = text
}
}
class MyNSTextField : NSTextField {
func customSetFont(font: NSFont?) {
super.font = font
}
override var font: NSFont? {
get {
return super.font
}
set {}
}
}
Maybe someone will come up with a cleaner solution to this, but you're right -- the normal methods for just setting .font on the NSTextField do not seem to work here. It seems to be because outside elements (the debugger doesn't give me a good hint) are trying to set the font to system font size 13.
So, my solution is to subclass NSTextField and make the setter for font not responsive. Then, I define a custom setter method, so the only way to get up to the real setter is through my custom method.
A little hacky, but it works.