Migrate legacy NeXTStep APIs to Cocoa/AppKit

[fwcd]

While the legacy NeXTStep API has substantial similarities to the modern AppKit, there are a number of differences, most notably including the change of the NX prefix to NS (but lots of other things have changed too over the last 30 years).

Discoveries

• Text is probably best migrated to NSTextView (rather than NSText), which provides access to text layouting internals
• NXRun can probably be migrated to NSTextStorage which inherits from NSMutableAttributedString, since NSTextView exposes its text storage
  • The implementation of HyperText relies quite heavily on storing references to Anchor instances in the info field. Since NSTextStorage is an attributed string under the hood, the easiest way to store custom data is probably to declare a custom attribute, so we do just that (AnchorAttributeName in HyperText)

Useful resources

• NeXTStep API
  • http://www.bitsavers.org/pdf/next/Release_1_Dec90/NEXTstep_Reference_Volume_2_Dec90.pdf
  • http://www.bitsavers.org/pdf/next/Release_3_Nov93/NeXTSTEP_Programming_Interface_Summary_Release_3_Nov93.pdf (PDF mirror)
  • https://www.nextop.de/NeXTstep_3.3_Developer_Documentation/
  • https://www.nextop.de/NeXTstep_3.3_Developer_Documentation/GeneralRef/02_ApplicationKit/Classes/Text.htmld/index.html
• Cocoa
  • NSTextView: https://developer.apple.com/documentation/appkit/nstextview
  • NSTextStorage: https://developer.apple.com/documentation/uikit/nstextstorage
  • Its attributeRuns or paragraphs might be close to NeXTStep's theRuns
  • TextKit (might be useful to port NXRun etc): https://developer.apple.com/documentation/appkit/textkit
  • https://developer.apple.com/documentation/uikit/textkit/display_text_with_a_custom_layout
  • (Archived, but extensive and quite useful) legacy docs:
  • Text architecture
    • https://developer.apple.com/library/archive/documentation/TextFonts/Conceptual/CocoaTextArchitecture/Introduction/Introduction.html
    • https://developer.apple.com/library/archive/documentation/TextFonts/Conceptual/CocoaTextArchitecture/TextSystemArchitecture/ArchitectureOverview.html
    • https://developer.apple.com/library/archive/documentation/TextFonts/Conceptual/CocoaTextArchitecture/TextAttributes/AboutTextAttributes.html
  • Text layout
    • https://developer.apple.com/library/archive/documentation/Cocoa/Conceptual/TextLayout/TextLayout.html
    • https://developer.apple.com/library/archive/documentation/Cocoa/Conceptual/TextLayout/Tasks/StringHeight.html
  • Text attributes
    • https://developer.apple.com/library/archive/documentation/Cocoa/Conceptual/TextAttributes/TextAttributes.html
  • Attributed strings
    • https://developer.apple.com/library/archive/documentation/Cocoa/Conceptual/AttributedStrings/AttributedStrings.html
  • Rulers
    • https://developer.apple.com/library/archive/documentation/Cocoa/Conceptual/Rulers/Rulers.html

[chrisbrandow]

I got interested in this myself, and started trying to understand the Text class, as well as its property theRuns. As you may already be aware, I the NXRun class is akin to NSRange, but contains the attributes being applied to a section of text.

I looked at CoreText documentation, and some vestiges of this may be present:

from the documentation of CTRunDelegate

A run delegate is assigned to a run (attribute range) to control typographic traits such glyph ascent, glyph descent, and glyph width.

https://developer.apple.com/documentation/coretext/ctrundelegate?language=objc

update:

more to the point is the CTRun class https://developer.apple.com/documentation/coretext/ctrun?language=objc

update further:

There are likely many good examples, but this project on GH implements a TextView markup in CoreText based in relevant parts on CTRun: https://github.com/LiveUI/FTCoreText/tree/master