Desert Moon (Posts about Software Development)

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.

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.

Git Default Branches: from master to main

Mitch Chapman — Sun, 09 Oct 2022 14:28:47 GMT

Short Form

$ cd old_repository
$ git branch -m master main
$ git push -u origin main

$ ssh my_hosting_provider
my_hosting_provider$ cd code_repos/my_bare_repo.git
my_hosting_provider$ git symbolic-ref HEAD refs/heads/main

my_hosting_provider$ exit
$ git push origin --delete master

Detecting Polygon Collisions Using SAT

Mitch Chapman — Tue, 21 Dec 2021 17:45:49 GMT

Detecting and resolving collisions between point-mass particles is pretty straightforward. See the previous post on "Simulating Lift: Particle-Particle Collisions". But how does one detect collisions between particles and a 2D polygon, e.g., an airfoil shape?

Simulating Lift: Particle-Particle Collisions

Mitch Chapman — Sat, 18 Dec 2021 23:04:03 GMT

In 2020 I complained about superficial explanations of how wings work. That post left me wondering whether a particle-based fluid simulation could manifest lift.

The short answer: yes.

If not GPG, then what?

Mitch Chapman — Sat, 15 Feb 2020 14:05:24 GMT

Sometimes you need to keep secrets. Maybe you are involved in organized crime or a revolutionary organization. Maybe you need safe-keeping for your build system credentials.

In my very limited experience, gpg is painful to use.

I've tried to use Hashicorp Vault, but I'm not sure I've understood its documentation. I think it recommends storing secrets in a vault on a dedicated secret server, and connecting to that server via a well-known URL when you need authentication tokens. And if/when that server needs to restart? Require three separate humans to manually, interactively, apply their keys to unlock the vault and get things running again.

Yikes.

What are the alternatives?

Darned if I know. But I just tripped across this post by Latacora and am grateful to its author(s). The recommendations seem to be:

For secure chat, use Signal. (Or WhatsApp? Really?)
Don't encrypt email. [Insert long list of failure modes.]
Use Magic Wormhole or Signal to send files securely.
Use tarsnap to encrypt backups.
Use signify or Minisign to sign packages.
Use libsodium to encrypt application data.

Fundamental Interconnectedness

Mitch Chapman — Tue, 20 Nov 2018 13:10:26 GMT

From twitter:

@McFaul: Hey @Grady_Booch, I want to learn Python. Whats your recommendation for how at my stage in life?

@Grady_Booch: Hey @gvanrossum you have another fan.

Professor Michael McFaul is a former U.S. Ambassador to Russia.

Grady Booch is perhaps best known for developing UML.

Guido van Rossum is the creator of Python, the programming language (and community) that has made my professional life so interesting.

Suddenly I wonder: is my twitter feed the product of a travesty generator?