macOS Custom Icon + Persistence (#8230)

This PR aims to improve custom icons on macOS in the following ways. (I
based this PR on the discussion #3631)

### Currently
- Current Icon customizations are not persistent *(when closing the
application the icon in dock reverts back to official icon)*
- There is no officially supported way to change icon to be something
completely custom.

### After this PR
- Current icon customizations are persistent (closing the application no
longer reverts back to official icon)
- Ghostty config `macos-icon` has a new option `custom` which by default
looks for icon `~/.config/ghostty/Ghostty.icns`. It has an accompanying
new configuration `macos-custom-icon` which allows for a different path
to be specified, it does support more than just `.icns` as well.

Both changes are based on the thread with @sfsam in
https://github.com/ghostty-org/ghostty/discussions/3631#discussioncomment-12180647

Feedback is always welcome, if I have not done something up to par
please let me know and I will do my best to correct it.

NOTE: I did notice some newlines with indents which seems to be against
convention in those files so I removed the whitespace if this is not
preferred I can revert.

---

P.S. Thanks for all the work you put into making an awesome terminal!

macos/Sources/App/macOS/AppDelegate.swift

@@ -119,6 +119,9 @@ class AppDelegate: NSObject,
     @Published private(set) var appIcon: NSImage? = nil {
         didSet {
             NSApplication.shared.applicationIconImage = appIcon
+            let appPath = Bundle.main.bundlePath
+            NSWorkspace.shared.setIcon(appIcon, forFile: appPath, options: [])
+            NSWorkspace.shared.noteFileSystemChanged(appPath)
         }
     }
 
@@ -255,13 +258,13 @@ class AppDelegate: NSObject,
 
         // Setup signal handlers
         setupSignals()
-        
+
         // If we launched via zig run then we need to force foreground.
         if Ghostty.launchSource == .zig_run {
             // This never gets called until we click the dock icon. This forces it
             // activate immediately.
             applicationDidBecomeActive(.init(name: NSApplication.didBecomeActiveNotification))
-            
+
             // We run in the background, this forces us to the front.
             DispatchQueue.main.async {
                 NSApp.setActivationPolicy(.regular)
@@ -834,6 +837,13 @@ class AppDelegate: NSObject,
         case .xray:
             self.appIcon = NSImage(named: "XrayImage")!
 
+        case .custom:
+            if let userIcon = NSImage(contentsOfFile: config.macosCustomIcon) {
+                self.appIcon = userIcon
+            } else {
+                self.appIcon = nil // Revert back to official icon if invalid location
+            }
+
         case .customStyle:
             guard let ghostColor = config.macosIconGhostColor else { break }
             guard let screenColors = config.macosIconScreenColor else { break }

macos/Sources/Ghostty/Ghostty.Config.swift

@@ -164,7 +164,7 @@ extension Ghostty {
             let key = "window-position-x"
             return ghostty_config_get(config, &v, key, UInt(key.count)) ? v : nil
         }
-        
+
         var windowPositionY: Int16? {
             guard let config = self.config else { return nil }
             var v: Int16 = 0
@@ -301,6 +301,24 @@ extension Ghostty {
             return MacOSIcon(rawValue: str) ?? defaultValue
         }
 
+        var macosCustomIcon: String {
+            #if os(macOS)
+            let homeDirURL = FileManager.default.homeDirectoryForCurrentUser
+            let ghosttyConfigIconPath = homeDirURL.appendingPathComponent(
+                ".config/ghostty/Ghostty.icns",
+                conformingTo: .fileURL).path()
+            let defaultValue = ghosttyConfigIconPath
+            guard let config = self.config else { return defaultValue }
+            var v: UnsafePointer<Int8>? = nil
+            let key = "macos-custom-icon"
+            guard ghostty_config_get(config, &v, key, UInt(key.count)) else { return defaultValue }
+            guard let ptr = v else { return defaultValue }
+            return String(cString: ptr)
+            #else
+            return ""
+            #endif
+        }
+
         var macosIconFrame: MacOSIconFrame {
             let defaultValue = MacOSIconFrame.aluminum
             guard let config = self.config else { return defaultValue }

macos/Sources/Ghostty/Package.swift

@@ -280,6 +280,7 @@ extension Ghostty {
         case paper
         case retro
         case xray
+        case custom
         case customStyle = "custom-style"
     }
 

src/config/Config.zig

@@ -2735,6 +2735,8 @@ keybind: Keybinds = .{},
 ///  * `blueprint`, `chalkboard`, `microchip`, `glass`, `holographic`,
 ///    `paper`, `retro`, `xray` - Official variants of the Ghostty icon
 ///    hand-created by artists (no AI).
+///  * `custom` - Use a completely custom icon. The location must be specified
+///    using the additional `macos-custom-icon` configuration
 ///  * `custom-style` - Use the official Ghostty icon but with custom
 ///    styles applied to various layers. The custom styles must be
 ///    specified using the additional `macos-icon`-prefixed configurations.
@@ -2753,6 +2755,15 @@ keybind: Keybinds = .{},
 ///     effort.
 @"macos-icon": MacAppIcon = .official,
 
+/// The absolute path to the custom icon file.
+/// Supported formats include PNG, JPEG, and ICNS.
+///
+/// Defaults to `~/.config/ghostty/Ghostty.icns`
+///
+/// Note: This configuration is required when `macos-icon` is set to
+/// `custom`
+@"macos-custom-icon": ?[]const u8 = null,
+
 /// The material to use for the frame of the macOS app icon.
 ///
 /// Valid values:
@@ -6975,6 +6986,7 @@ pub const MacAppIcon = enum {
     paper,
     retro,
     xray,
+    custom,
     @"custom-style",
 };