WWDC Notes

Advanced Text Layouts and Effects with Text Kit

Show Apple's description.
Move beyond the basics and unlock the full power of Text Kit for advanced text handling in your apps. Understand how to use hit detection and pixel-perfect layout information for responding to user touches. Discover new text effects, including a sophisticated letterpress look, and dive deeper into the mechanics of Text Kit for displaying multi-page documents and custom layouts.

Text Effects (iOS 7)

We can obtain many text effects via the attribute (of a NSAttrributedString) NSTextEffectAttributeName.

Just checked: it’s 2018 (5 years later) and the only effect is still just NSAttributedString.TextEffectStyle.letterpressStyle

The Trio

In TextKit, there are three classes that are used to represent the text in the app and turn it into glyphs which users will see on screen.

NSTextStorage

  • Provides the backing store for the text in the app.
  • It’s a NSMutableAttributedString subclass: it controls the text unicode characters, attributes etc

NSLayoutManager

  • Manages how that text gets turned into glyphs and has customizable override points.
  • It takes the given text (from NSTextStorage) and translates it into glyphs on screen.
  • (Via delegation) We can accomplish advanced layout techniques such as folding lines or other advanced text rendering.

NSTextContainer

  • Describes the geometry about which the flow lines and line fragments in your text view.
  • Represents one area on the display in which you'd like to draw a text.

What is a text container?

A text container defines a coordinate system and geometry for an NSLayoutManager.

Exclusion paths live entirely in the NSTextContainer's coordinate space.

It does not do the actual drawing, that's up to your text view.

Hit-testing is also done in the NSTextContainer's coordinate space.
Hit testing returns the glyph that was tapped:

Above: Three characters, one glyph.

Note: one glyph is not a one-to-one mapping from a glyph to a set of characters or vice-versa.

Therefore we need to use the NSLayoutManager conversion:

This works chars to glyphs, too.

One NSLayoutManager can have multiple NSTextContainer, this is how we get multipage and multi column support almost for free.

With NSLayoutManager we can:

  • get the exact position and sizeof each single character 😍 (more precisely, of the glyph, which is font + character) and line
  • Modifying line spacing
  • Validating soft line breaking
  • Custom glyph mapping

More info here.

Missing anything? Corrections? Contributions are welcome 😃

Written by

zntfdr

Federico Zanetello

Federico Zanetello is an iOS Engineer with strong passion for Swift, minimalism, and design. When he’s not busy automating things, he can be found writing at fivestars.blog and/or playing with the latest shiny toys.