Mac / Cocoa – Getting a list of windows using Accessibility API

I don’t know a way to get window ID and PID from the Accessibility API.
The NSWindow method Laurent mentioned only provides Window IDs but not the PID of the window owning application.
I would use the CGWindowList methods that are available since 10.5.
To get a list of window IDs and the PID of the owner you can try the following:

CFArrayRef windowList = CGWindowListCopyWindowInfo(kCGWindowListOptionOnScreenOnly, kCGNullWindowID);
for (NSMutableDictionary* entry in (NSArray*)windowList) 
{
    NSString* ownerName = [entry objectForKey:(id)kCGWindowOwnerName];
    NSInteger ownerPID = [[entry objectForKey:(id)kCGWindowOwnerPID] integerValue];
    NSLog(@"%@:%d", ownerName, ownerPID);
}
CFRelease(windowList);  

You can control if you want all windows (including offscreen, …) with the option paramter.
Also the entry objects contain a lot more information. Documentation link

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