xM: improve the bundle icon a bit

1 files changed, 13 insertions, 21 deletions

diff --git a/xM/gen-icon.swift b/xM/gen-icon.swift
index 5e29016..712e9e6 100644
--- a/xM/gen-icon.swift
+++ b/xM/gen-icon.swift
@@ -1,4 +1,4 @@
-// gen-icon.awk: generate a program icon for xM in the Apple icon format
+// gen-icon.swift: generate a program icon for xM in the Apple icon format
 //
 // Copyright (c) 2023, Přemysl Eric Janouch <p@janouch.name>
 // SPDX-License-Identifier: 0BSD
@@ -10,24 +10,17 @@ import Foundation
 import ImageIO
 import UniformTypeIdentifiers
 
-// XXX: Not even AppKit provides real superelliptic squircles; screw it.
-func drawSquircle(context: CGContext, bounds: CGRect, radius: CGFloat) {
-	context.move(to: CGPointMake(bounds.minX, bounds.maxY - radius))
-	context.addArc(
-		center: CGPointMake(bounds.minX + radius, bounds.maxY - radius),
-		radius: radius, startAngle: .pi, endAngle: .pi / 2, clockwise: true)
-	context.addLine(to: CGPointMake(bounds.maxX - radius, bounds.maxY))
-	context.addArc(
-		center: CGPointMake(bounds.maxX - radius, bounds.maxY - radius),
-		radius: radius, startAngle: .pi / 2, endAngle: 0, clockwise: true)
-	context.addLine(to: CGPointMake(bounds.maxX, bounds.maxY - radius))
-	context.addArc(
-		center: CGPointMake(bounds.maxX - radius, bounds.minY + radius),
-		radius: radius, startAngle: 0, endAngle: .pi / -2, clockwise: true)
-	context.addLine(to: CGPointMake(bounds.minX + radius, bounds.minY))
-	context.addArc(
-		center: CGPointMake(bounds.minX + radius, bounds.minY + radius),
-		radius: radius, startAngle: .pi / -2, endAngle: .pi, clockwise: true)
+// Apple uses something that's close to a "quintic superellipse" in their icons,
+// but doesn't quite match. Either way, it looks better than rounded rectangles.
+func addSquircle(context: CGContext, bounds: CGRect) {
+	context.move(to: CGPoint(x: bounds.maxX, y: bounds.midY))
+	for theta in stride(from: 0.0, to: .pi * 2, by: .pi / 1e4) {
+		let x = pow(abs(cos(theta)), 2 / 5.0) * bounds.width / 2
+			* CGFloat(signOf: cos(theta), magnitudeOf: 1) + bounds.midX
+		let y = pow(abs(sin(theta)), 2 / 5.0) * bounds.height / 2
+			* CGFloat(signOf: sin(theta), magnitudeOf: 1) + bounds.midY
+		context.addLine(to: CGPoint(x: x, y: y))
+	}
 	context.closePath()
 }
 
@@ -42,8 +35,7 @@ func drawIcon(scale: CGFloat) -> CGImage? {
 	context.scaleBy(x: scale, y: scale)
 
 	let bounds = CGRectMake(100, 100, size.width - 200, size.height - 200)
-	// The radius was something like size.{width,height}/6.4, at least for iOS.
-	drawSquircle(context: context, bounds: bounds, radius: 180)
+	addSquircle(context: context, bounds: bounds)
 	let squircle = context.path!
 
 	// Gradients don't draw shadows, so draw it separately.