Android Studio Build:

Android Studio 4.0 Canary 1
Build #AI-192.6817.14.36.5959023, built on October 22, 2019
Runtime version: 1.8.0_212-release-1586-b4-5784211 amd64
VM: OpenJDK 64-Bit Server VM by JetBrains s.r.o
Linux 5.0.0-32-generic
GC: ParNew, ConcurrentMarkSweep
Memory: 1981M
Cores: 8
Registry: ide.new.welcome.screen.force=true, debugger.watches.in.variables=false
Non-Bundled Plugins: CheckStyle-IDEA

Version of Gradle Plugin: 4.0.0-alpha01
Version of Gradle: 5.6.1
Version of Kotlin: 1.3.60-eap-25
OS: Ubuntu 19.04

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Steps to Reproduce:
1. UnZIP the attached project and import it into Android Studio
2. Run the app
3. Start recording a screencast (e.g., from Android Studio)
4. Tap the "Show Dialog" button to show an AlertDialog
5. Wait a moment
6. Tap the "OK" button again to dismiss that dialog
7. Stop recording the screencast
8. Look at the screencast

Expected Results: The screencast to be completely empty, as we are recording the functionality of an activity that has FLAG_SECURE set

Actual Results: The AlertDialog appears in the screencast

The attached MP4 is a screencast taken of this app, using a Pixel 4 running Android 10.

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If you are going to create a Window with WindowManager, you need to see whether we are in a secure window now and propagate that secure status. Otherwise, we wind up in the same situation that we have with the View-based UI framework, where FLAG_SECURE misses lots of content (menus, Spinner, dialogs, toasts, etc.), because we do not control those windows and cannot set FLAG_SECURE on them. See https://github.com/commonsguy/cwac-security/blob/master/docs/FLAGSECURE.md and https://issuetracker.google.com/issues/37100029 for historical context.

I think that Dialog should handle FLAG_SECURE itself, either implicitly or via a WindowSecurityPolicy value (see https://issuetracker.google.com/issues/143778148 for more on that). While it is theoretically possible for use to maintain a SecureDialog composable that adds FLAG_SECURE, we would also need to maintain a SecureAlertDialog composable, along with Secure... variants of everything else in Compose that uses Dialog.

Given that you know whether a DialogWrapper needs to be secure, making it secure is a matter of updating the dialog's window's flags:

if (markAsSecure) window?.setFlags(WindowManager.LayoutParams.FLAG_SECURE, WindowManager.LayoutParams.FLAG_SECURE)

(assumed to be in the init block of DialogWrapper)

Thanks for considering this!