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Converting Fonts Manually

NSFontManager defines a number of methods for explicitly converting particular traits and characteristics of a font. Table 1 lists these conversion methods.

Each method returns a transformed version of the font provided, or the original font if it can’t be converted. convertFont:toFace: and convertFont:toFamily: both alter the basic design of the font provided. The first method requires a fully specified typeface name, such as “Times-Roman” or “Helvetica-BoldOblique”, while the second expects only a family name, such as “Times” or “Helvetica”.

The convertFont:toHaveTrait: and convertFont:toNotHaveTrait: methods use trait masks to add or remove a single trait such as Italic, Bold, Condensed, or Extended.

The convertFont:toSize: method returns a font of the requested size, with all other characteristics the same as those of the original font.

The convertWeight:ofFont: method either increases or decreases the weight of the font provided, according to a Boolean flag. Font weights are typically indicated by a series of names, which can vary from font to font. Some go from Light to Medium to Bold, while others have Book, SemiBold, Bold, and Black. This method offers a uniform way of incrementing and decrementing any font’s weight.

The default implementation of font conversion is very conservative, making a change only if no other trait or aspect is affected. For example, if you try to convert Helvetica Oblique 12.0 point by adding the Bold trait, and only Helvetica Bold is available, the font isn’t converted. You can create a subclass of NSFontManager and override the conversion methods to perform less conservative conversion, perhaps using Helvetica Bold in this case and losing the Oblique trait.

In addition to the font-conversion methods, NSFontManager defines fontWithFamily:traits:weight:size: to construct a font with a given set of characteristics. If you don’t care to make a subclass of NSFontManager, you can use this method to perform approximate font conversions yourself.

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