Casting NSFont to CGFont — impossible?

Question

I try to cast NSFont to CGFont:

 var defaultFont: NSFont = NSFont.labelFont(ofSize: CGFloat(currentSize))

Like this:

 if let oldFont = defaultFont as? CGFont {...

No way, compiler says ”no”: Conditional downcast to CoreFoundation type 'CGFont' will always succeed. OK, let's try different way:

 let oldFont = defaultFont as CGFont

Nope. Compiler says ”no”: 'NSFont' is not convertible to 'CGFont'; did you mean to use 'as!' to force downcast?. OK, let's use as!:

 let oldFont = defaultFont as! CGFont

Copmpiler says ”yes”!, But runtime error says: Thread 1: EXC_BAD_INSTRUCTION (code=EXC_I386_INVOP, subcode=0x0)

I tried initiate CGFont by name, but not all my fonts are "mounted in system", and font name could change from Font-Name to Font_name if its initiated by CGFont(_ name:CFString). It's risky.

Any help?

`NSFont` does not extend `CGFont` and they are not bridged. So no, you can't cast in any way. — rmaddy, Jul 04 '19 at 20:19
`if let x = "Hello world" as? CGFont { }` also produces the compiler error “Conditional downcast to CoreFoundation type 'CGFont' will always succeed” – very strange. — Martin R, Jul 04 '19 at 20:35
@Łukasz: Did you have a chance to check the answer? It would be nice to know if the suggested code works in your case. — Martin R, Jul 09 '19 at 08:54

score 4 · Accepted Answer · edited Jun 20 '20 at 09:12

4

From https://lists.apple.com/archives/cocoa-dev/2010/Feb/msg00177.html:

Given an NSFont object how can I extract or create a CGFontRef from it to use directly with CoreGraphics?

You're close. Starting in (I think) Leopard, NSFont and CTFontRef (not CGFontRef) are toll-free bridged, so you should be able to use CTFontCopyGraphicsFont() to get a CGFontRef from an NSFont.

Example:

import CoreText

let defaultFont: NSFont = ...
let cgFont = CTFontCopyGraphicsFont(defaultFont, nil)

edited Jun 20 '20 at 09:12

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answered Jul 04 '19 at 20:23

Martin R

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Likely duplicate of https://stackoverflow.com/questions/4942711/how-do-i-get-an-nsfont-object-from-a-cgfont-or-ctfont-object – matt Jul 04 '19 at 20:24
That's the other way around. – Martin R Jul 04 '19 at 20:25

Casting NSFont to CGFont — impossible?

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