RFR: 8326712: Robot tests fail on XWayland

[Alexander Zvegintsev]

On Wed, 26 Jun 2024 11:25:37 GMT, Alexander Zvegintsev <azvegint at openjdk.org> wrote:

> Most of the headful test failures on XWayland are due to screen capture is not working.
> 
> Wayland, unlike X11, does not allow arbitrary applications to capture the screen contents directly.
> Instead, screen capture functionality is managed by the compositor, which can enforce stricter controls and permissions, requiring explicit user approval for screen capture operations.
> 
> This issue is already resolved in OpenJDK ([base issue](https://bugs.openjdk.org/browse/JDK-8280982), there are  subsequent fixes) by using the [ScreenCast XDG portal](https://flatpak.github.io/xdg-desktop-portal/docs/doc-org.freedesktop.portal.ScreenCast.html).
> 
> The XDG ScreenCast portal is utilized for capturing screen data as it provides a secure and standardized method for applications to access screen content.
> Additionally, it allows for the reuse of user permissions without requiring repeated confirmations, streamlining the user experience and enhancing convenience.
> 
> 
> <hr>
> 
> So this changeset is a copy of the OpenJDK fixes with the addition of the JavaFX customization. 
> For ease of review, you can skip the changes in the first two commits:
> - First commit is a direct copy of files from OpenJDK
> - Second commit removes the `gtk-` prefix before the `gtk_...` and `g_...` function calls (in AWT all gtk functions are dynamically loaded, we don't need that in JavaFX).
> 
> properties added:
> 
> - `javafx.robot.screenshotMethod`, accepts `gtk`(existing gtk method) and `dbusScreencast`(added by this changeset, used by default for Wayland)
> - `javafx.robot.screenshotDebug` prints debug info if it is set to `true`
> 
> <hr>
> 
> What are the remaining issues?
> 
> 1.
> 
> After applying this fix, system tests will pass except for the `SwingNodeJDialogTest` test.
> 
> This interop test calls `java.awt.Robot#getPixelColor` which internally `gtk->g_main_context_iteration(NULL, TRUE);` causes a blocking of javafx gtk loop, so the test hangs.
> So a change is required on OpenJDK side to fix this issue.
> 
> 2.
> 
> Even after solving the `#1`, the `SwingNodeJDialogTest.testNodeRemovalBeforeShow` case is still failing.
> 
> 3.
> 
> Internally the ScreenCast session keeps open for [2s](https://github.com/openjdk/jdk/blob/d457609f700bbb1fed233f1a04501c995852e5ac/src/java.desktop/unix/classes/sun/awt/screencast/ScreencastHelper.java#L62).
> This is to reduce overhead in case of frequent consecutive screen captures.
> 
> There is a crash when an AWT ScreenCast session overlaps with the FX ScreenCast session.  E.g.  `java.awt.Robot#getPixelColor()` and `jav...

modules/javafx.graphics/src/main/java/com/sun/glass/ui/gtk/screencast/ScreencastHelper.java line 220:

> 218:             throw new SecurityException(
> 219:                     "Screen Capture in the selected area was not allowed"
> 220:             );

@kevinrushforth 
I think this SecurityException should be removed, as it is not mentioned in the javadoc for the `getPixelColor` or `getScreenCapture`.  And we also do not want to throw another runtime exception.

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PR Review Comment: https://git.openjdk.org/jfx/pull/1490#discussion_r1658303570