For the past couple of weeks I’ve been building Rocketeer, an iOS browser for the Gemini network.^[1] The gemtext format is very minimal, so I thought it would be fairly easy to build something to render Gemini documents. The format is line-oriented and only allows a few different line types. There are regular paragraphs, link lines, 3 levels of headings, unordered list items, preformatted blocks, and block quotes. All of these are pretty simple, visually speaking, and the layout is also straightforward. So, I expected to be able to build a renderer quite easily. Unfortunately, there turned out to be lots of little details that were not so obvious at first and introduced a bunch of complications.

In my last post, I went over the implementation of a custom SwiftUI view that wraps UITextView in order to make it non-scrolling and auto-expanding. That worked quite well, but in continuing the reimplementation of Tusker’s compose screen in SwiftUI, I ran into a couple more things I had to re-implement myself.

I’m currently in the process of rewriting the Compose screen in Tusker to use SwiftUI. This has mostly been a smooth process, but there have been a few hiccups, the first of which was the main text box. The updates to SwiftUI introduced in iOS 14 included TextEditor, the SwiftUI equivalent of UITextView to allow multi-line text editing. Unfortunately, there’s no (straightforward) way of disabling scrolling, making it unsuitable for some designs where the text view is embedded in a separate scroll view. Additionally, the fact that it’s not available at all on iOS 13 means layouts that require non-scrolling multi-line text editors must wrap UITextView themselves in order to be achievable with SwiftUI.

Gemini is a small protocol bulit on top of TCP and TLS that’s designed to serve as a transport mechanism primarily for text documents while lacking a great deal of the complexity of HTTP. Network.framework was introduced to Apple’s platforms in 2018 as a modern framework for dealing with network connections and building custom network protocols. So, let’s use it to build a Gemini client implementation.

Update: See the follow up for info about adapting this to TextKit 2.

In iOS 13, Apple replaced the Peek and Pop force touch system with new context menus and previews^[1]. These new previews have a fancy animation for when the appear, in which they expand out of the content and onto the screen. Back when I first replaced the previews in Tusker with the new context menus (over a year ago, shortly after WWDC19), I wanted to replicate the behavior in Safari for links and mentions in post bodies. At the time, there was pretty much zero official documentation about the new context menu APIs, so I decided to wait for either Apple to publish docs or for someone else to figure it out first. Now that WWDC20 has come and gone, and I’ve been working on it a little bit at a time for over a year, I finally have a fully working implementation.