How can I get a list of all windows, currently on the screen, in swift?

Question

How can I get a list of all windows, currently on the screen, in swift? (all examples are preceded by import Cocoa)

In objective-c I can run the following code successfully:

CFArrayRef windowList = CGWindowListCopyWindowInfo(kCGWindowListOptionOnScreenOnly, kCGNullWindowID);

But when I run the equivalent in swift(using the playground to test):

let windowList = CGWindowListCopyWindowInfo(kCGWindowListOptionOnScreenOnly, kcGNullWindowID)

I get an error telling me that I have an Use of unresolved identifier 'kcGNullWindowID'.

After playing around with the help of the quartz documentation for a while I have gotten to:

let windowList = CGWindowListCopyWindowInfo(CGWindowListOption(kCGWindowListOptionOnScreenOnly), CGWindowListOption(0))

But it still does not work as I am receiving a {__NSArrayM} object, which I do not know how to access.

Am I on the right track or am I doing something fundamentally wrong?

Is the objc version, `CGWindowListCopyWindowInfo` thread safe? Or does it have to run from main thread? — Noitidart, Aug 06 '15 at 22:48

score 23 · Accepted Answer · answered Jul 12 '15 at 11:52

Here's an example in Swift 2.0, which also demonstrates multiple options.

    let options = CGWindowListOption(arrayLiteral: CGWindowListOption.ExcludeDesktopElements, CGWindowListOption.OptionOnScreenOnly)
    let windowListInfo = CGWindowListCopyWindowInfo(options, CGWindowID(0))
    let infoList = windowListInfo as NSArray? as? [[String: AnyObject]]

score 6 · Answer 2 · edited Jun 07 '14 at 07:45

Use takeUnretainedValue() or takeRetainedValue() on windowList.

Check out Apple's Using Swift with Cocoa and Objective-C and read the section called Working with Cocoa Data Types and look for Unmanaged Objects.

Here is a concrete example:

import Cocoa

let windowInfosRef = CGWindowListCopyWindowInfo(CGWindowListOption(kCGWindowListOptionOnScreenOnly), CGWindowID(0))
let windowInfos = windowInfosRef.takeRetainedValue().__conversion() // cast to swift dictionary
println(windowInfos) // print the swift dictionary

score 1 · Answer 3 · answered May 28 '15 at 19:19

Here's my version for Swift 1.2. It's more explicit about types, since we know the function returns an array of dictionaries with string keys.

let options = CGWindowListOption(kCGWindowListOptionOnScreenOnly)
let cfInfoList = CGWindowListCopyWindowInfo(options, CGWindowID(0)).takeRetainedValue()
let infoList = cfInfoList as NSArray as? [[String: AnyObject]]

How can I get a list of all windows, currently on the screen, in swift?

3 Answers3

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