Detecting screen recording settings on macOS Catalina - macos

Question

What's is a reliable way to detect if user has enabled this API?
CGWindowListCreateImage returns a valid object even if screen recording API is disabled. There are multiple combinations possible (kCGWindowListOptionIncludingWindow, kCGWindowListOptionOnScreenBelowWindow) and only some will return NULL.
- (CGImageRef)createScreenshotImage
{
NSWindow *window = [[self view] window];
NSRect rect = [window frame];
rect.origin.y = NSHeight([[window screen] frame]) - NSMaxY([window frame]);
CGImageRef screenshot = CGWindowListCreateImage(
rect,
kCGWindowListOptionIncludingWindow,
//kCGWindowListOptionOnScreenBelowWindow,
0,//(CGWindowID)[window windowNumber],
kCGWindowImageBoundsIgnoreFraming);//kCGWindowImageDefault
return screenshot;
}
The only reliable way is through CGDisplayStreamCreate which is risky as Apple always changes privacy settings every year.
- (BOOL)canRecordScreen
{
if (#available(macOS 10.15, *)) {
CGDisplayStreamRef stream = CGDisplayStreamCreate(CGMainDisplayID(), 1, 1, kCVPixelFormatType_32BGRA, nil, ^(CGDisplayStreamFrameStatus status, uint64_t displayTime, IOSurfaceRef frameSurface, CGDisplayStreamUpdateRef updateRef) {
;
});
BOOL canRecord = stream != NULL;
if (stream) {
CFRelease(stream);
}
return canRecord;
} else {
return YES;
}
}

Answer 1

All of the solutions presented here have a flaw in one way or another. The root of the problem is that there's no correlation between your permission to know about a window (via the name in the window list), your permission to know about the process owner of the window (such as WindowServer and Dock). Your permission to view the pixels on screen is a combination of two sparse sets of information.
Here is a heuristic that covers all the cases as of macOS 10.15.1:
BOOL canRecordScreen = YES;
if (#available(macOS 10.15, *)) {
canRecordScreen = NO;
NSRunningApplication *runningApplication = NSRunningApplication.currentApplication;
NSNumber *ourProcessIdentifier = [NSNumber numberWithInteger:runningApplication.processIdentifier];
CFArrayRef windowList = CGWindowListCopyWindowInfo(kCGWindowListOptionOnScreenOnly, kCGNullWindowID);
NSUInteger numberOfWindows = CFArrayGetCount(windowList);
for (int index = 0; index < numberOfWindows; index++) {
// get information for each window
NSDictionary *windowInfo = (NSDictionary *)CFArrayGetValueAtIndex(windowList, index);
NSString *windowName = windowInfo[(id)kCGWindowName];
NSNumber *processIdentifier = windowInfo[(id)kCGWindowOwnerPID];
// don't check windows owned by this process
if (! [processIdentifier isEqual:ourProcessIdentifier]) {
// get process information for each window
pid_t pid = processIdentifier.intValue;
NSRunningApplication *windowRunningApplication = [NSRunningApplication runningApplicationWithProcessIdentifier:pid];
if (! windowRunningApplication) {
// ignore processes we don't have access to, such as WindowServer, which manages the windows named "Menubar" and "Backstop Menubar"
}
else {
NSString *windowExecutableName = windowRunningApplication.executableURL.lastPathComponent;
if (windowName) {
if ([windowExecutableName isEqual:#"Dock"]) {
// ignore the Dock, which provides the desktop picture
}
else {
canRecordScreen = YES;
break;
}
}
}
}
}
CFRelease(windowList);
}
If canRecordScreen is not set, you'll need to put up some kind of dialog that warns the user that they'll only be able to see the menubar, desktop picture, and the app's own windows. Here's how we presented it in our app xScope.
And yes, I'm still bitter that these protections were introduced with little regard to usability.

Answer 2

Apple provides direct low level api to check for access and grant access. No need to use tricky workarounds.
/* Checks whether the current process already has screen capture access */
#available(macOS 10.15, *)
public func CGPreflightScreenCaptureAccess() -> Bool
Use the above functions to check for screen capture access.
if access is not given use the below function to prompt for access
/* Requests event listening access if absent, potentially prompting */
#available(macOS 10.15, *)
public func CGRequestScreenCaptureAccess() -> Bool
Screenshot taken from documentation

Answer 3

#marek-h posted a good example that can detect the screen recording setting without showing privacy alert.
Btw, #jordan-h mentioned that this solution doesn't work when the app presents an alert via beginSheetModalForWindow.
I found that SystemUIServer process is always creating some windows with names: AppleVolumeExtra, AppleClockExtra, AppleBluetoothExtra ...
We can't get the names of these windows, before the screen recording is enabled in Privacy preferences. And when we can get one of these names at least, then it means that the user has enabled screen recording.
So we can check the names of the windows (created by SystemUIServer process) to detect the screen recording preference, and it works fine on macOS Catalina.
#include <AppKit/AppKit.h>
#include <libproc.h>
bool isScreenRecordingEnabled()
{
if (#available(macos 10.15, *)) {
bool bRet = false;
CFArrayRef list = CGWindowListCopyWindowInfo(kCGWindowListOptionAll, kCGNullWindowID);
if (list) {
int n = (int)(CFArrayGetCount(list));
for (int i = 0; i < n; i++) {
NSDictionary* info = (NSDictionary*)(CFArrayGetValueAtIndex(list, (CFIndex)i));
NSString* name = info[(id)kCGWindowName];
NSNumber* pid = info[(id)kCGWindowOwnerPID];
if (pid != nil && name != nil) {
int nPid = [pid intValue];
char path[PROC_PIDPATHINFO_MAXSIZE+1];
int lenPath = proc_pidpath(nPid, path, PROC_PIDPATHINFO_MAXSIZE);
if (lenPath > 0) {
path[lenPath] = 0;
if (strcmp(path, "/System/Library/CoreServices/SystemUIServer.app/Contents/MacOS/SystemUIServer") == 0) {
bRet = true;
break;
}
}
}
}
CFRelease(list);
}
return bRet;
} else {
return true;
}
}

Answer 4

I'm not aware of an API that's specifically for getting the screen recording permission status. Besides creating a CGDisplayStream and checking for nil, the Advances in macOS Security WWDC presentation also mentioned that certain metadata from the CGWindowListCopyWindowInfo() API will not be returned unless permission is granted. So something like this does seem to work, although it has the same issue of relying on implementation details of that function:
private func canRecordScreen() -> Bool {
guard let windows = CGWindowListCopyWindowInfo([.optionOnScreenOnly], kCGNullWindowID) as? [[String: AnyObject]] else { return false }
return windows.allSatisfy({ window in
let windowName = window[kCGWindowName as String] as? String
return windowName != nil
})
}

Answer 5

As of Nov19 chockenberry has correct answer.
As #onelittlefish pointed out the kCGWindowName is being omitted in case user has not enabled the screen recording access in privacy pane. This method also doesn't trigger the privacy alert.
- (BOOL)canRecordScreen
{
if (#available(macOS 10.15, *)) {
CFArrayRef windowList = CGWindowListCopyWindowInfo(kCGWindowListOptionOnScreenOnly, kCGNullWindowID);
NSUInteger numberOfWindows = CFArrayGetCount(windowList);
NSUInteger numberOfWindowsWithName = 0;
for (int idx = 0; idx < numberOfWindows; idx++) {
NSDictionary *windowInfo = (NSDictionary *)CFArrayGetValueAtIndex(windowList, idx);
NSString *windowName = windowInfo[(id)kCGWindowName];
if (windowName) {
numberOfWindowsWithName++;
} else {
//no kCGWindowName detected -> not enabled
break; //breaking early, numberOfWindowsWithName not increased
}
}
CFRelease(windowList);
return numberOfWindows == numberOfWindowsWithName;
}
return YES;
}

Answer 6

The most favorable answer is not exactly right, he left out some sences, like sharing state.
we can find the answer in WWDC(https://developer.apple.com/videos/play/wwdc2019/701/?time=1007)
Here are some excerpts from WWDC:
the window name and sharing state are not available, unless the user has preapproved the app for screen recording. And this is because some apps put sensitive data such as account names or more likely web page URLs in the window's name.
- (BOOL)ScreeningRecordPermissionCheck {
if (#available(macOS 10.15, *)) {
CFArrayRef windowList = CGWindowListCopyWindowInfo(kCGWindowListOptionOnScreenOnly, kCGNullWindowID);
NSUInteger numberOfWindows = CFArrayGetCount(windowList);
NSUInteger numberOfWindowsWithInfoGet = 0;
for (int idx = 0; idx < numberOfWindows; idx++) {
NSDictionary *windowInfo = (NSDictionary *)CFArrayGetValueAtIndex(windowList, idx);
NSString *windowName = windowInfo[(id)kCGWindowName];
NSNumber* sharingType = windowInfo[(id)kCGWindowSharingState];
if (windowName || kCGWindowSharingNone != sharingType.intValue) {
numberOfWindowsWithInfoGet++;
} else {
NSNumber* pid = windowInfo[(id)kCGWindowOwnerPID];
NSString* appName = windowInfo[(id)kCGWindowOwnerName];
NSLog(#"windowInfo get Fail pid:%lu appName:%#", pid.integerValue, appName);
}
}
CFRelease(windowList);
if (numberOfWindows == numberOfWindowsWithInfoGet) {
return YES;
} else {
return NO;
}
}
return YES;
}

Answer 7

As of MacOS 10.15.7 the heuristics of obtaining window-names for visible windows, and so know we have screen-capture permission, doesn't always work. Sometimes we just don't find valid windows we can query, and would wrongly deduce we don't have permissions.
However, I found another way to directly query (using sqlite) the Apple TCC database - the model where permissions are persisted. The screen-recording permissions are to be found in the "System level" TCC database ( residing in /Library/Application Support/com.apple.TCC/TCC.db). If you open the database using sqlite, and query: SELECT allowed FROM access WHERE client="com.myCompany.myApp" AND service="kTCCServiceScreenCapture" you'll get your answer.
Two downsides comparing to other answers:
to open this TCC.db database, your app must have "Full Disk Access" permission. It doesn't need to run with 'root' privileges, and root privileges won't help if you don't have the "Full disk access".
it takes about 15 millisec to run, which is slower than querying the window list.
The up side -- it's a direct query of the actual thing, and does not rely on any windows, or processes to exist at the time of query.
Here's some draft code to do this:
NSString *client = #"com.myCompany.myApp";
sqlite3 *tccDb = NULL;
sqlite3_stmt *statement = NULL;
NSString *pathToSystemTCCDB = #"/Library/Application Support/com.apple.TCC/TCC.db";
const char *pathToDBFile = [pathToSystemTCCDB fileSystemRepresentation];
if (sqlite3_open(pathToDBFile, &tccDb) != SQLITE_OK)
return nil;
const char *query = [[NSString stringWithFormat: #"SELECT allowed FROM access WHERE client=\"%#\" AND service=\"kTCCServiceScreenCapture\"",client] UTF8String];
if (sqlite3_prepare_v2(tccDb, query , -1, &statement, nil) != SQLITE_OK)
return nil;
BOOL allowed = NO;
while (sqlite3_step(statement) == SQLITE_ROW)
allowed |= (sqlite3_column_int(statement, 0) == 1);
if (statement)
sqlite3_finalize(statement);
if (tccDb)
sqlite3_close(tccDb);
return #(allowed);
}

Answer 8

Working for me.
Code from: https://gist.github.com/code4you2021/270859c71f90720d880ccb2474f4e7df
import Cocoa
struct ScreenRecordPermission {
static var hasPermission: Bool {
permissionCheck()
}
static func permissionCheck() -> Bool {
if #available(macOS 10.15, *) {
let runningApplication = NSRunningApplication.current
let processIdentifier = runningApplication.processIdentifier
guard let windows = CGWindowListCopyWindowInfo([.optionOnScreenOnly], kCGNullWindowID)
as? [[String: AnyObject]],
let _ = windows.first(where: { window -> Bool in
guard let windowProcessIdentifier = (window[kCGWindowOwnerPID as String] as? Int).flatMap(pid_t.init),
windowProcessIdentifier != processIdentifier,
let windowRunningApplication = NSRunningApplication(processIdentifier: windowProcessIdentifier),
windowRunningApplication.executableURL?.lastPathComponent != "Dock",
let _ = window[String(kCGWindowName)] as? String
else {
return false
}
return true
})
else {
return false
}
}
return true
}
static func requestPermission() {
if #available(macOS 10.15, *) {
CGWindowListCreateImage(CGRect(x: 0, y: 0, width: 1, height: 1), .optionOnScreenOnly, kCGNullWindowID, [])
}
}
}
# how to use
# print("hasPermission: ", ScreenRecordPermission.hasPermission)

Answer 9

The above answer is not working fine. Below is the correct answer.
private var canRecordScreen : Bool {
guard let windows = CGWindowListCopyWindowInfo([.optionOnScreenOnly], kCGNullWindowID) as? [[String: AnyObject]] else { return false }
return windows.allSatisfy({ window in
let windowName = window[kCGWindowName as String] as? String
let isSharingEnabled = window[kCGWindowSharingState as String] as? Int
return windowName != nil || isSharingEnabled == 1
})
}