Hannes Oud hannesoid

libdispatch efficiency tips

The libdispatch is one of the most misused API due to the way it was presented to us when it was introduced and for many years after that, and due to the confusing documentation and API. This page is a compilation of important things to know if you're going to use this library. Many references are available at the end of this document pointing to comments from Apple's very own libdispatch maintainer (Pierre Habouzit).

My take-aways are:

You should create very few, long-lived, well-defined queues. These queues should be seen as execution contexts in your program (gui, background work, ...) that benefit from executing in parallel. An important thing to note is that if these queues are all active at once, you will get as many threads running. In most apps, you probably do not need to create more than 3 or 4 queues.
Go serial first, and as you find performance bottle necks, measure why, and if concurrency helps, apply with care, always validating under system pressure. Reuse

	NSScrollView* container = [[NSScrollView alloc] initWithFrame:CGRectMake(0, 0, 200, 100)];
	container.hasVerticalScroller = YES;
	container.hasHorizontalScroller = YES;
	container.wantsLayer = YES;
	container.identifier = [@(LOGVIEW_OFFSET + i) stringValue];

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	clipview.autoresizesSubviews = YES;
	clipview.autoresizingMask = NSViewWidthSizable \| NSViewHeightSizable;

	import Foundation
	import IOKit

	func getMACAddress() -> String {
	let matching = IOServiceMatching("IOEthernetInterface") as NSMutableDictionary
	matching[kIOPropertyMatchKey] = ["IOPrimaryInterface": true]
	var servicesIterator: io_iterator_t = 0
	defer { IOObjectRelease(servicesIterator) }

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	#!/bin/bash

	### Get my uid
	UserID=`id -u`
	echo "Your UID: ${UserID}"

	### Unload root process
	sudo launchctl unload /Library/LaunchDaemons/com.antelopeaudio.daemon.plist

	### Kill the process if it was already awaken

	import SwiftUI

	extension CGRect {
	fileprivate func point(anchor: UnitPoint) -> CGPoint {
	var point = self.origin
	point.x += self.size.width * anchor.x
	#if os(macOS)
	point.y += self.size.height * (1 - anchor.y)
	#else
	point.y += self.size.height * anchor.y

	static const CGFloat kFontWeightEpsilon = FLT_EPSILON;

	@implementation UIFont (CustomizedDynamicType)

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	textStyle:(nonnull UIFontTextStyle)textStyle {
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	textStyle:textStyle
	fontWeight:UIFontWeightRegular
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	# Git branch in command prompts
	autoload -Uz vcs_info
	precmd() {vcs_info}
	setopt PROMPT_SUBST

	# the last part of this command dictates what is shown for git info, referenced later by the prompt command.
	# here, showing branch name %b in color 38 (blue) and the repo name %r in color 226 (yellow)
	zstyle ':vcs_info:git:*' formats '%F{38}%b%f %F{226}(%r)%f'

	# can set both the left (PROMPT) and right (RPROMPT) prompts

	import Foundation

	// Props to @pteasima and @MichalKleinJr:
	// https://twitter.com/pteasima/status/1544723987606929408?s=21&t=JL1oIuL87Ms_VPBQBZQ7Rg
	public extension AsyncSequence {
	func eraseToAsyncStream() -> AsyncStream<Element> {
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	let task = Task {
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	public extension Task {
	/// Cancels this `Task` when the surrounding `Task` is cancelled.
	/// This is necessary if `Task {}` and `Task.detached {}`
	/// should be automatically cancelled - otherwise, such Tasks
	/// just run until finished.
	///
	/// Usage:
	///
	/// await Task { await myAsyncFunc() }.autoCancel()
	func autoCancel() async -> Void {

	import InterposeKit
	import SwiftUI

	/// A workaround for an issue in SwiftUI related to delayed highlighting of list rows upon user
	/// interaction, rendering it inconsistent with UIKit.
	///
	/// This fix implements the solution proposed by Léo Natan and utilizes `InterposeKit` by Peter
	/// Steinberger to modify the behavior of `UICollectionViewCell` instances used internally
	/// by SwiftUI.
	///