Get window information using Core Graphics

window.m

#import <stdio.h>
#import <sys/sysctl.h>
#import <unistd.h>
#import <Foundation/Foundation.h>
#import <CoreGraphics/CoreGraphics.h>


/* Returns the parent of any arbitrary process, more flexible than
 * getpid() and getppid().
 */
pid_t get_parent_pid(pid_t pid)
{
    struct kinfo_proc proc;
    size_t proc_size = sizeof(proc);
    int mib[4] = { CTL_KERN, KERN_PROC, KERN_PROC_PID, pid };

    if (sysctl(mib, 4, &proc, &proc_size, NULL, 0) == -1) {
        perror("sysctl");
        return -1;
    }

    return proc.kp_eproc.e_ppid;
}


void follow_pid(pid_t pid)
{
    fprintf(stderr, "Following pid chain\n");
    while (pid > 0) {
        pid = get_parent_pid(pid);
        fprintf(stderr, "  - %u\n", pid);
    }
}


int main(int argc, char **argv)
{
    NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];

    pid_t myPID = getpid();
    fprintf(stderr, "my pid = %u\n", myPID);
    follow_pid(myPID);

    CFArrayRef windowInfo = CGWindowListCopyWindowInfo(kCGWindowListOptionOnScreenOnly, kCGNullWindowID);
    /* fprintf(stderr, "windowInfo at %p\n", windowInfo); */

    CFIndex windowCount = CFArrayGetCount(windowInfo);
    /* fprintf(stderr, "Found %ld windows\n", windowCount); */

    for (long i = 0; i < windowCount; ++i) {
        NSDictionary *windowDict = (__bridge NSDictionary *) CFArrayGetValueAtIndex(windowInfo, i);
        NSLog(@"%@", windowDict);
    }

    [pool release];
    return 0;
}