Detecting screen recording settings on macOS Catalina
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.
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