Get Active Window Dynamic By Objective-C

main.m

#import <Foundation/Foundation.h>
#import <AppKit/AppKit.h>

#include <unistd.h> // getopt


int
GetFrontMostAppPid(void) {
    NSRunningApplication *app = [[NSWorkspace sharedWorkspace]
            frontmostApplication];
    pid_t pid = [app processIdentifier];
    return pid;
}

CFStringRef
getAppTitle(pid_t pid) {
    CFStringRef title = NULL;
    // Get the process ID of the frontmost application.
    // NSRunningApplication* app = [[NSWorkspace sharedWorkspace]
    //                        frontmostApplication];
    // pid_t pid = [app processIdentifier];

    // See if we have accessibility permissions, and if not, prompt the user to
    // visit System Preferences.
    NSDictionary *options = @{(__bridge id) kAXTrustedCheckOptionPrompt: @YES};
    Boolean appHasPermission = AXIsProcessTrustedWithOptions(
            (__bridge CFDictionaryRef) options);
    if (!appHasPermission) {
        return title; // we don't have accessibility permissions
    }
    // Get the accessibility element corresponding to the frontmost application.
    AXUIElementRef appElem = AXUIElementCreateApplication(pid);
    if (!appElem) {
        return title;
    }

    // Get the accessibility element corresponding to the frontmost window
    // of the frontmost application.
    AXUIElementRef window = NULL;
    if (AXUIElementCopyAttributeValue(appElem,
            kAXFocusedWindowAttribute, (CFTypeRef *) &window) != kAXErrorSuccess) {
        CFRelease(appElem);
        return title;
    }

    // Finally, get the title of the frontmost window.
    AXError result = AXUIElementCopyAttributeValue(window, kAXTitleAttribute,
            (CFTypeRef *) &title);

    // At this point, we don't need window and appElem anymore.
    CFRelease(window);
    CFRelease(appElem);

    if (result != kAXErrorSuccess) {
        // Failed to get the window title.
        return title;
    }

    // Success! Now, do something with the title, e.g. copy it somewhere.

    // Once we're done with the title, release it.
    // CFRelease(title);

    return title;
}


@interface AppFocus : NSObject
@end

@implementation AppFocus
- (id)init {
    self = [super init];
    if (!self)
        return self;

    NSNotificationCenter *center = NSWorkspace.sharedWorkspace.notificationCenter;
    [center addObserver:self
               selector:@selector(didActivateApp:)
                   name:NSWorkspaceDidActivateApplicationNotification
                 object:nil];

    return self;
}

- (void)didActivateApp:(NSNotification *)d {
    NSRunningApplication *app = d.userInfo[NSWorkspaceApplicationKey];
//    getAppTitle(app.processIdentifier);
    NSString *title = (__bridge NSString *) getAppTitle(app.processIdentifier);
    NSLog(@"%s\n", app.localizedName.UTF8String);
    NSLog(title);
//    fflush(stdout);
}
@end

void print_usage(FILE *stream) {
    fprintf(stream, "usage: app-focus\n");
    fprintf(stream, "\n");
    fprintf(stream, "print notifications to the console when different apps take focus on OS X\n");
    fprintf(stream, "\n");
    fprintf(stream, "options\n");
    fprintf(stream, "  -h              print this message and exit\n");
}


int main(int argc, char **argv) {
    int c;
    while ((c = getopt(argc, argv, "h")) != EOF) {
        switch (c) {
            case 'h':
                print_usage(stdout);
                return 0;
            case '?':
                print_usage(stderr);
                return 1;
        }
    }

    @autoreleasepool {
        NSRunLoop *runLoop = NSRunLoop.currentRunLoop;
        AppFocus *af = [[AppFocus alloc] init];
        while ([runLoop runMode:NSDefaultRunLoopMode beforeDate:[NSDate dateWithTimeIntervalSinceNow:2]]);
    };
    return 0;
}