Desert Moon

Portugal 2025

Mitch Chapman — Sun, 12 Apr 2026 21:56:45 GMT

In April of 2025, Bobi and I traveled to Portugal to visit friends and see the country. These are my notes from the trip.

At the beach with Rick and Laura

More Fundamental Interconnectedness

Mitch Chapman — Thu, 01 Jan 2026 01:51:47 GMT

Post by @dabeaz@mastodon.social

View on Mastodon

This is as cool as that time on Twitter when former Russian Ambassador Michael McFaul asked Grady Booch (!) for recommendations on how to learn Python (!?) - and Mr. Booch tagged Guido van Rossum.

EV Roadtrip Efficiency

Mitch Chapman — Fri, 30 May 2025 21:14:15 GMT

marimo makes for a pretty nice notebook environment. I've been using it to compare the energy efficiency of my Tesla Model 3 vs. the Volkswagen ID.4 that has replaced it.

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Fractional Indexing

Mitch Chapman — Wed, 31 Jul 2024 14:58:33 GMT

A couple of years ago I built a macOS/iOS data logging app for personal use. When I started work on it, I considered using a bespoke server and CRDTs to maintain data consistency among instances of the app. It was fun to learn the basics of CRDTs and to build a few prototypes. But I'm lazy, so I ended up using CloudKit.

Sometimes I come across a blog post that makes me wish I'd pursued the server + CRDT approach. Today the trigger was Bartosz Sypytkowski's Non-interleaving Linear Sequence (LSeq) CRDT.

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Custom validation messages w. Svelte

Mitch Chapman — Mon, 13 Feb 2023 18:16:21 GMT

Example.svelte

<script lang="ts">
let control: HTMLInputElement
function validate() {
    if (control.validity.valueMissing) {
        control.setCustomValidity('Please provide a date of birth.')
    }
}
<script>

<input
  type="date"
  bind:this="{control}"
  required
  on:invalid="{validate}"
  on:change="{validate}"
  on:input="{validate}"
  title="A required input" />

<style>
  *:required::after {
    font-size: 125%;
    vertical-align: top;
    content: '*';
    color: red;
  }
</style>

Result

SvelteKit Session Management

Mitch Chapman — Sat, 11 Feb 2023 16:04:38 GMT

tl;dr: Manage session cookies using hooks.server.ts, the handle function, event.locals and app.d.ts.

Testing SwiftUI Tables

Mitch Chapman — Mon, 09 Jan 2023 14:09:00 GMT

I maintain a macOS SwiftUI app whose user interface contains a Table, one with a bound sortOrder.

The app's Xcode project contains UI tests that exercise the sorting logic, by clicking on the column headers. These tests are really fragile. Odds are good that any new release of macOS, or Xcode, or SwiftUI, will break them.

I'm not sure why they're so fragile. I suspect the way SwiftUI generates the underlying view hierarchy for a Table may still be in flux.

In any case, here is what I'm currently using to click on the column headers of a SwiftUI Table. This is for macOS 13.1, Xcode 14.2, Swift 5.7, SwiftUI 4.2.11.

    private func clickTableColumnHeaders(tableEl: XCUIElement) {
        for column in tableEl.tableColumns.allElementsBoundByIndex {
            let height = column.frame.height
            // Assume the column header lies above the column.
            let y = CGFloat(-10.0)
            let offset = CGVector(dx: 0.5, dy: y / height)
            let coords = column.coordinate(withNormalizedOffset: offset)
            // Click twice to exercise both sort orders.
            coords.click()
            coords.click()
        }
    }

Svelte's Take on ObservableObject

Mitch Chapman — Mon, 05 Dec 2022 13:33:06 GMT

SwiftUI's ObservableObject and @Published make it easy to group related properties into a single class, and to react to changes of individual properties.

I recently complained to my friend, Bobi, that Svelte seemed lacking in this regard. Its tutorials always show components whose exportable state is defined by separate, top-level variable declarations.

    let count = 0;

    $: if (count >= 10) {
        alert('count is dangerously high!');
        ...

She set me straight: if you want to group related, observable properties, just use a writable store whose value is an Object (or if you prefer, a class instance). Whenever any property is changed, interested parties react automatically.

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WINGS Cigarette Cards

Mitch Chapman — Mon, 14 Nov 2022 16:46:34 GMT

WINGS Cigarette Cards

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macOS, Xcode, Ventura: When CloudKit Stops Syncing

Mitch Chapman — Tue, 08 Nov 2022 19:43:01 GMT

(This is for future reference, when this sort of problem arises again.)

Last spring I started working on a pair (macOS, iOS) of personal utility applications. They relied on CloudKit storage. For months they worked well together. Then, as soon as I updated to macOS 13 Ventura, they stopped syncing.

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