Bold and Italic fonts issue - Cocoa

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C

macOS

Objective-C

I am trying to make cocoa application draw bold or/and italic fonts. Here is the code I use:

NSFontTraitMask fontStyle = 0;
if (m_bBold)
    fontStyle |= NSBoldFontMask;
if (m_bItalic)
    fontStyle |= NSItalicFontMask;

NSFontManager* fontManager = [NSFontManager sharedFontManager];
NSFont* font               = [fontManager fontWithFamily:@"Helvetica" traits:fontStyle weight:5 size:12];

As far as I understand all that fontManager does is just convert to the correct font name.
So it works fine. It converts Helvetica to Helvetica-Bold or Verdana to Verdana-Bold.

However, the displayed font is not always what I asked. For example, It works with Verdana (I see it bold). But it does not works with Helvetica. Although the name is converted to Helvetica-Bold, the fonts are still regular.

What is the mistake here?