feat: handle cli commands: --list and --focus=window_id

alt-tab-macos.xcodeproj/project.pbxproj

@@ -130,6 +130,7 @@
 		BF0C894199BB262BDB2D8D37 /* InfoPlist.strings in Resources */ = {isa = PBXBuildFile; fileRef = BF0C8221101CD179DB1121D5 /* InfoPlist.strings */; };
 		BF0C894325A54CF0B6B53464 /* Localizable.strings in Resources */ = {isa = PBXBuildFile; fileRef = BF0C8B8B31D2F421AC258351 /* Localizable.strings */; };
 		BF0C896B5D08B7DA8F2024AC /* KeyRepeatTimer.swift in Sources */ = {isa = PBXBuildFile; fileRef = BF0C8D606B53D315F2D9927B /* KeyRepeatTimer.swift */; };
+		BF0C8973EC078169170F2634 /* CliEvents.swift in Sources */ = {isa = PBXBuildFile; fileRef = BF0C8C69316EAAF6DC9AE391 /* CliEvents.swift */; };
 		BF0C898511686611E4D7D81E /* Button.swift in Sources */ = {isa = PBXBuildFile; fileRef = BF0C8B2C057099EDABE46779 /* Button.swift */; };
 		BF0C89B4B17D7843C32A102E /* Markdown.swift in Sources */ = {isa = PBXBuildFile; fileRef = BF0C8353097840D7DB1E0E2E /* Markdown.swift */; };
 		BF0C89C49CFBAAB4646BB8CB /* InfoPlist.strings in Resources */ = {isa = PBXBuildFile; fileRef = BF0C82A8848224E76B880A83 /* InfoPlist.strings */; };
@@ -451,6 +452,7 @@
 		BF0C8C5210ACA9FBFAE9C631 /* preferences-general.jpg */ = {isa = PBXFileReference; lastKnownFileType = image.jpeg; path = "preferences-general.jpg"; sourceTree = "<group>"; };
 		BF0C8C5B74E5DA2CC31E52F4 /* extract_l10n_strings.sh */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = text.script.sh; path = extract_l10n_strings.sh; sourceTree = "<group>"; };
 		BF0C8C5C0FF5D567BF190DE5 /* ApplicationServices.HIServices.framework.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = ApplicationServices.HIServices.framework.swift; sourceTree = "<group>"; };
+		BF0C8C69316EAAF6DC9AE391 /* CliEvents.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = CliEvents.swift; sourceTree = "<group>"; };
 		BF0C8C6995992F837A9A83A6 /* ca */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = text.plist.strings; name = ca; path = InfoPlist.strings; sourceTree = "<group>"; };
 		BF0C8C77273E00B019725640 /* add_missing_terms_on_poeditor.ts */ = {isa = PBXFileReference; lastKnownFileType = file.ts; path = add_missing_terms_on_poeditor.ts; sourceTree = "<group>"; };
 		BF0C8CA36F8BD99BF38A45D0 /* bn */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = text.plist.strings; name = bn; path = InfoPlist.strings; sourceTree = "<group>"; };
@@ -1777,6 +1779,7 @@
 				BF0C869E544F968051715452 /* SystemAppearanceEvents.swift */,
 				BF0C8B5D1A9658E64F8ECB56 /* SystemScrollerStyleEvents.swift */,
 				BF0C8643F524515224BF1618 /* KeyboardEventsTestable.swift */,
+				BF0C8C69316EAAF6DC9AE391 /* CliEvents.swift */,
 			);
 			path = events;
 			sourceTree = "<group>";
@@ -2325,6 +2328,7 @@
 				BF0C8E366BC25171C0A3881C /* ApplicationServices.HIServices.framework.swift in Sources */,
 				BF0C803A13C409E7F01FBCAB /* SkyLight.framework.swift in Sources */,
 				BF0C80C69EFEF93C18539925 /* PreferencesMigrations.swift in Sources */,
+				BF0C8973EC078169170F2634 /* CliEvents.swift in Sources */,
 			);
 			runOnlyForDeploymentPostprocessing = 0;
 		};

src/api-wrappers/HelperExtensions.swift

@@ -314,3 +314,14 @@ extension NSPoint {
         return NSPoint(x: lhs.x / Double(rhs), y: lhs.y / Double(rhs))
     }
 }
+
+extension Optional {
+    enum Error: Swift.Error {
+        case unexpectedNil
+    }
+
+    // useful call multiple statements that could fail, and have a unique do-catch block to handle failures
+    func unwrapOrThrow() throws -> Wrapped {
+        if let self { return self } else { throw Error.unexpectedNil }
+    }
+}

src/logic/BackgroundWork.swift

@@ -11,6 +11,7 @@ class BackgroundWork {
     static var systemPermissionsThread: BackgroundThreadWithRunLoop!
     static var repeatingKeyThread: BackgroundThreadWithRunLoop!
     static var missionControlThread: BackgroundThreadWithRunLoop!
+    static var cliEventsThread: BackgroundThreadWithRunLoop!
     static let screenshotsDispatchGroup = DispatchGroup()
 
     // swift static variables are lazy; we artificially force the threads to init
@@ -29,6 +30,8 @@ class BackgroundWork {
         repeatingKeyThread = BackgroundThreadWithRunLoop("repeatingKeyThread", .userInteractive)
         // we main Mission Control state on a background thread. We protect reads from main-thread with an NSLock
         missionControlThread = BackgroundThreadWithRunLoop("missionControlThread", .userInteractive)
+        // we listen to CLI commands (CFMessagePort events)
+        cliEventsThread = BackgroundThreadWithRunLoop("cliEventsThread", .userInteractive)
     }
 
     static func startCrashReportsQueue() {

src/logic/events/CliEvents.swift

@@ -0,0 +1,104 @@
+class CliEvents {
+    static let portName = "com.lwouis.alt-tab-macos.cli"
+
+    static func observe() {
+        var context = CFMessagePortContext(version: 0, info: nil, retain: nil, release: nil, copyDescription: nil)
+        if let messagePort = CFMessagePortCreateLocal(nil, portName as CFString, handleEvent, &context, nil),
+           let source = CFMessagePortCreateRunLoopSource(nil, messagePort, 0) {
+            CFRunLoopAddSource(BackgroundWork.cliEventsThread.runLoop, source, .commonModes)
+        } else {
+            Logger.error("Can't listen on message port. Is another AltTab already running?")
+            // TODO: should we quit or restart here?
+            // It's complex since AltTab can be restarted sometimes,
+            // and the new instance may coexit with the old for some duration
+            // There is also the case of multiple instances at login
+        }
+    }
+}
+
+fileprivate func handleEvent(_: CFMessagePort?, _: Int32, _ data: CFData?, _: UnsafeMutableRawPointer?) -> Unmanaged<CFData>? {
+    Logger.debug()
+    if let data = data,
+       let message = String(data: data as Data, encoding: .utf8) {
+        Logger.info(message)
+        let output = CliServer.executeCommandAndSendReponse(message)
+        if let responseData = try? CliServer.jsonEncoder.encode(output) as CFData {
+            return Unmanaged.passRetained(responseData)
+        }
+    }
+    Logger.error("Failed to decode message")
+    return nil
+}
+
+class CliServer {
+    static let jsonEncoder = JSONEncoder()
+    static let error = "error"
+    static let noOutput = "noOutput"
+
+    static func executeCommandAndSendReponse(_ rawValue: String) -> Codable {
+        var output: Codable = ""
+        DispatchQueue.main.sync {
+            if rawValue == "--list" {
+                output = JsonOutput(windows: Windows.list
+                    .filter { !$0.isWindowlessApp }
+                    .map { JsonWindow(id: $0.cgWindowId, title: $0.title) }
+                )
+                return
+            }
+            if rawValue.hasPrefix("--focus=") {
+                if let id = CGWindowID(rawValue.dropFirst("--focus=".count)),
+                   let window = (Windows.list.first { $0.cgWindowId == id }) {
+                    window.focus()
+                    output = noOutput
+                    return
+                }
+            }
+            output = error
+        }
+        return output
+    }
+}
+
+struct JsonOutput: Codable {
+    var windows: [JsonWindow]
+}
+
+struct JsonWindow: Codable {
+    var id: CGWindowID?
+    var title: String
+}
+
+class CliClient {
+    static func detectCommand() -> String? {
+        let args = CommandLine.arguments
+        if args.count == 2 && !args[1].starts(with: "--logs=") {
+            if args[1] == "--list" || args[1].hasPrefix("--focus=") {
+                return args[1]
+            }
+        }
+        return nil
+    }
+
+    static func sendCommandAndProcessResponse(_ command: String) {
+        do {
+            let serverPortClient = try CFMessagePortCreateRemote(nil, CliEvents.portName as CFString).unwrapOrThrow()
+            let data = try command.data(using: .utf8).unwrapOrThrow()
+            var returnData: Unmanaged<CFData>?
+            let _ = CFMessagePortSendRequest(serverPortClient, 0, data as CFData, 2, 2, CFRunLoopMode.defaultMode.rawValue, &returnData)
+            let responseData = try returnData.unwrapOrThrow().takeRetainedValue()
+            if let response = String(data: responseData as Data, encoding: .utf8) {
+                if response != "\"\(CliServer.error)\"" {
+                    if response != "\"\(CliServer.noOutput)\"" {
+                        print(response)
+                    }
+                    exit(0)
+                }
+            }
+            print("Couldn't execute command. Is it correct?")
+            exit(1)
+        } catch {
+            print("AltTab.app needs to be running for CLI commands to work")
+            exit(1)
+        }
+    }
+}

src/main.swift

@@ -1,6 +1,10 @@
 import AppKit
 import Darwin
 
+if let command = CliClient.detectCommand() {
+    CliClient.sendCommandAndProcessResponse(command)
+}
+
 // - if the app is quit/force-quit from Activity Monitor, it will receive SIGTERM and applicationWillTerminate won't be called
 // - if the app crashes in swift code (e.g. unexpected nil object), SIGTRAP is sent
 // we intercept these signals, and do an emergency exit

src/ui/App.swift

@@ -317,7 +317,9 @@ extension App: NSApplicationDelegate {
             KeyboardEvents.addEventHandlers()
             MouseEvents.observe()
             TrackpadEvents.observe()
+            CliEvents.observe()
             self.preloadWindows()
+            Logger.info("AltTab ready")
             #if DEBUG
 //            self.showPreferencesWindow()
             #endif