8335468: [XWayland] JavaFX hangs when calling java.awt.Robot.getPixelColor #22131

azvegint · 2024-11-15T01:35:16Z

This is a linux only issue and this PR contains two parts(they are available as two separate commits):

a. 8335468: [XWayland] JavaFX hangs when calling java.awt.Robot.getPixelColor
b. 8335469: [XWayland] crash when an AWT ScreenCast session overlaps with an FX ScreenCast session

b. is not reproducible without a. being fixed.

More about both cases:

a.

Previously we used a blocking g_main_context_iteration call, this prevents normal execution if there is a GTK main loop running in the process.

Now we are handling 3 cases:

If there is no GTK main loop running
Example: just a JDK only application.
In this case we call g_main_context_iteration(NULL, TRUE) as before (when gtk_main_level() == 0).
If there is a GTK main loop running, but we are not requesting pixels on its thread
Example: application showing a JFXPanel, but are requesting pixels from a main thread.
Now we are not trying to block thread: g_main_context_iteration(NULL, FALSE) (when gtk_main_level() > 0) .
If there is a GTK main loop running, and we are requesting pixels on its thread
Example: a JavaFX application trying to get pixels on the FX application thread, e.g. from a button callback.
Now we go nested with gtk_main()

jdk commit

b.

After fixing a. the crash appears:

Internally the ScreenCast session keeps open for 2s (both JDK and JFX, and their implementations are almost identical).
This is to reduce overhead in case of frequent consecutive screen captures.

When we perform a cleanup to close the session, we internally call pw_deinit.

It becomes a problem if these sessions overlap in time, so that the second session cleanup crashes when it tries to call pipewire functions without initializing the pipewire system by pw_init (please note that This function can be called multiple times.).

So the solution is not to call pw_deinit because we don't really need it, and it needs to be applied to both the JDK and JavaFX.

jdk commit / jfx commit
FX review counterpart

Testing in different scenarios looks good.

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Issue

JDK-8335468: [XWayland] JavaFX hangs when calling java.awt.Robot.getPixelColor (Bug - P3)

Reviewers

Kevin Rushforth (@kevinrushforth - Author)
Harshitha Onkar (@honkar-jdk - Reviewer)

Reviewing

Using git

Checkout this PR locally:
$ git fetch https://git.openjdk.org/jdk.git pull/22131/head:pull/22131
$ git checkout pull/22131

Update a local copy of the PR:
$ git checkout pull/22131
$ git pull https://git.openjdk.org/jdk.git pull/22131/head

Using Skara CLI tools

Checkout this PR locally:
$ git pr checkout 22131

View PR using the GUI difftool:
$ git pr show -t 22131

Using diff file

Download this PR as a diff file:
https://git.openjdk.org/jdk/pull/22131.diff

Using Webrev

Link to Webrev Comment

…Color

…h an FX ScreenCast session

bridgekeeper · 2024-11-15T01:36:09Z

👋 Welcome back azvegint! A progress list of the required criteria for merging this PR into master will be added to the body of your pull request. There are additional pull request commands available for use with this pull request.

openjdk · 2024-11-15T01:37:03Z

@azvegint This change now passes all automated pre-integration checks.

ℹ️ This project also has non-automated pre-integration requirements. Please see the file CONTRIBUTING.md for details.

After integration, the commit message for the final commit will be:

8335468: [XWayland] JavaFX hangs when calling java.awt.Robot.getPixelColor

Reviewed-by: kcr, honkar

You can use pull request commands such as /summary, /contributor and /issue to adjust it as needed.

At the time when this comment was updated there had been 200 new commits pushed to the master branch:

7be94d0: 8344891: Remove uses of sun.misc.ReflectUtil in java.desktop
822a155: 8341427: JFR: Adjust object sampler span handling
d00f311: 8343150: Change URLClassLoader.getPermissions to return empty PermissionCollection
effee12: 8344533: CTW: Add option to remove clinits before loading
70c4e2c: 8344587: Reduce number of "jdk.jpackage.internal" classes used from other packages
1114704: 6672644: JComboBox still scrolling if switch to another window and return back
98b6678: 8343741: SA jstack --mixed should print information about VM locks
1b2d9ca: 8344881: Problemlist java/awt/Robot/InfiniteLoopException.java on Linux
6aec2dc: 8344788: Specify that the access control context parameters of Subject.doAsPrivileged are ignored
079f503: 8344568: Renaming ceil_log2 to log2i_ceil
... and 190 more: https://git.openjdk.org/jdk/compare/db56266ad164b4ecae59451dc0a832097dbfbd8e...master

As there are no conflicts, your changes will automatically be rebased on top of these commits when integrating. If you prefer to avoid this automatic rebasing, please check the documentation for the /integrate command for further details.

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openjdk · 2024-11-15T01:37:43Z

@azvegint The following label will be automatically applied to this pull request:

client

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mlbridge · 2024-11-15T02:13:04Z

Webrevs

00: Full (19956fda)

kevinrushforth

Looks good. I tested it on an Ubuntu 24.04 system running Wayland both with and without the FX fix in openjdk/jfx#1639

kevinrushforth · 2024-11-18T20:46:03Z

@honkar-jdk or @prrace Do one of you want to review this?

honkar-jdk · 2024-11-18T21:18:56Z

@honkar-jdk or @prrace Do one of you want to review this?

Sure Kevin. I can take a look at it later today.

honkar-jdk · 2024-11-20T02:12:31Z

Tested the changes on Ubuntu 24.04 with JDK alone (without JFX fix) and did not observe any issues in Robot related tests (automated + manual). Since this is an interop fix, I'll be testing it JDK + JFX fix next.

honkar-jdk

LGTM, tested without/with jdk fix and without/with jfx fix combinations.
Interop tests work as expected with jdk + jfx fix.

azvegint · 2024-11-25T11:10:17Z

/integrate

openjdk · 2024-11-25T11:11:32Z

Going to push as commit 965aace.
Since your change was applied there have been 212 commits pushed to the master branch:

811d08c: 8340010: Fix vectorization tests with compact headers
519bb26: 8344217: Remove calls to SecurityManager and doPrivileged in java.net.DatagramSocket and java.net.NetMulticastSocket after JEP 486 integration
d112f35: 8344855: Remove calls to SecurityManager and doPrivileged in HTTP related implementation classes in the sun.net and sun.net.www.http packages after JEP 486 integration
da4b7a8: 8341436: containers/docker/TestJcmdWithSideCar.java takes needlessly long to run
333a997: 8335231: [macos] Test java/awt/print/PrinterJob/Cancel/PrinterJobCancel.java failed on macOS because the case didn't get the expected PrintAbortException
9576546: 8343698: Linux x86_64 lto build gives a lot of warnings and fails lto-wrapper: fatal error: make returned 2 exit status
68ba7ee: 8340205: Native linker allows MemoryLayout consisting of only PaddingLayout
6f622da: 8344923: Problem list on java/awt/Robot/ScreenCaptureRobotTest.java on macOS
8f08020: 8344903: Improve error handling TestJhsdbJstackPrintVMLocks.java
a83cfe2: 8344917: Fix recent NULL usage backsliding
... and 202 more: https://git.openjdk.org/jdk/compare/db56266ad164b4ecae59451dc0a832097dbfbd8e...master

Your commit was automatically rebased without conflicts.

openjdk · 2024-11-25T11:11:39Z

@azvegint Pushed as commit 965aace.

💡 You may see a message that your pull request was closed with unmerged commits. This can be safely ignored.

azvegint added 2 commits November 15, 2024 00:50

8335468: [XWayland] JavaFX hangs when calling java.awt.Robot.getPixel…

f439eb9

…Color

8335469: [XWayland] crash when an AWT ScreenCast session overlaps wit…

19956fd

…h an FX ScreenCast session

openjdk bot added the client [email protected] label Nov 15, 2024

azvegint mentioned this pull request Nov 15, 2024

8335469: [XWayland] crash when an AWT ScreenCast session overlaps with an FX ScreenCast session openjdk/jfx#1639

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azvegint mentioned this pull request Jul 7, 2025

8361524: [XWayland] possible JavaFX interop hang #26172

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8335468: [XWayland] JavaFX hangs when calling java.awt.Robot.getPixelColor #22131

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