CGGetOnlineDisplayList usage in Swift

Question

Level 1

5 points

CGGetOnlineDisplayList usage in Swift

I realize this might be more of a developer question but I'm not building an app … just trying to get my display resolutions.

I'm not using Xcode … just swift from the command line so I can just have a swift file not a project.

https://developer.apple.com/library/mac/documentation/GraphicsImaging/Reference/ Quartz_Services_Ref/

gives

funcCGGetOnlineDisplayList(_

maxDisplays

: UInt32,

_

onlineDspys

: UnsafeMutablePointer<CGDirectDisplayID>,

_

dspyCnt

: UnsafeMutablePointer<UInt32>) -> CGError

but not a simple example of usage so I have no idea how to set up the variables and use them afterwards

( which I'm guessing will be looping through the displays and using CGDisplayPixelsHigh and CGDisplayPixelsWide)

Posted on Apr 29, 2015 1:45 PM

Reply

Answer 1

Questor Author

Level 1

5 points

Apr 30, 2015 1:52 PM in response to Questor

This seems to work after much tweaking.

Now I need help to compile it to work on older operating systems. Help appreciated.

% swift main.swift

ID is 418876289

dspyCnt is 1

currentDisplay is 418876289

CGDisplayPixelsHigh(currentDisplay) is 1080

CGDisplayPixelsWide(currentDisplay) is 1920

% swiftc main.swift -o main

<unknown>:0: error: cannot load underlying module for 'CoreGraphics'

<unknown>:0: note: did you forget to set an SDK using -sdk or SDKROOT?

<unknown>:0: note: use "xcrun -sdk macosx swift" to select the default OS X SDK installed with Xcode

----------------------------- main.swift -----------------------------

import Foundation

import CoreGraphics

var mainID = CGMainDisplayID()

println("ID is \(mainID)")

var dErr: CGError

let maxDisplays: UInt32 = 16

var onlineDspys: [CGDirectDisplayID] = [mainID]

var dspyCnt: UInt32 = 0

dErr = CGGetOnlineDisplayList(maxDisplays, &onlineDspys, &dspyCnt)

println("dspyCnt is \(dspyCnt)")

for currentDisplay in onlineDspys {

println("currentDisplay is \(currentDisplay)")

println("CGDisplayPixelsHigh(currentDisplay) is \(CGDisplayPixelsHigh(currentDisplay))")

println("CGDisplayPixelsWide(currentDisplay) is \(CGDisplayPixelsWide(currentDisplay))")

}

Reply

Answer 2

Questor Author

Level 1

5 points

May 4, 2015 7:16 AM in response to Questor

Nope. Does not set the onlineDspys array correctly so I still need help.

Reply