RFR: 8324941: POC for Headless platform for JavaFX [v11]

[Kevin Rushforth]

On Tue, 22 Jul 2025 07:09:58 GMT, Johan Vos <jvos at openjdk.org> wrote:

>> After spending a year in the sandbox repository, the Headless Platform is now ready to be reviewed in the main repository.
>> 
>> ### the Headless Platform
>> The Headless Platform is a top-level com.sun.glass.ui platform that replaces the second-level Monocle-Headless subplatform, that is part of the top-level Monocle platform. 
>> The platform can be used like any other platform, especially for running headless JavaFX applications, or for running tests (e.g. on CI systems)
>> 
>> ### changes
>> The code for the Headless Platform is in a new package com.sun.glass.ui.headless in the javafx.graphics module, and it does not require a code change in other packages.
>> This PR adds a simple change in the `build.gradle` file, to make the Headless Platform the standard when running headless tests (instead of using Monocle/Headless)
>> 
>> ### enable the Headless Platform
>> Setting the system property `glass.platform` to `Headless` will select the Headless Platform instead of the default one (either gtk, mac or win).
>> 
>> ### testing
>> `gradlew --info -PHEADLESS_TEST=true -PFULL_TEST=true :systemTests:cleanTest :systemTests:test`
>> runs all the system tests, apart from the robot tests. There are 2 failing tests, but there are valid reasons for those to fail.
>> 
>> ### robot tests
>> Most of the robot tests are working on headless as well. add `-PUSE_ROBOT` to test those.
>
> Johan Vos has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Add copyright sections

I'll review the code soon. I ran a full set of tests, excluding the robot tests, and see two failures (below), which you mentioned are expected. Presumably these are the same two failures you see?

It would probably be best to skip these two tests when running the Headless glass platform. This could either be done as part of this PR or in a follow-up "Skip failing tests on Headless glass platform" bug.

1. MacPasteboardTest


MacPasteboardTest > testValidLocalImageURLMacPasteboard() FAILED
    java.lang.NullPointerException: Cannot invoke "com.sun.glass.ui.mac.MacPasteboardShim.pushMacPasteboard(java.util.HashMap)" because "test.com.sun.glass.ui.mac.MacPasteboardTest.macPasteboardShim" is null
        at test.com.sun.glass.ui.mac.MacPasteboardTest.lambda$testValidLocalImageURLMacPasteboard$0(MacPasteboardTest.java:73)

MacPasteboardTest > testDataBase64ImageMacPasteboard() FAILED
    java.lang.NullPointerException: Cannot invoke "com.sun.glass.ui.mac.MacPasteboardShim.pushMacPasteboard(java.util.HashMap)" because "test.com.sun.glass.ui.mac.MacPasteboardTest.macPasteboardShim" is null
        at test.com.sun.glass.ui.mac.MacPasteboardTest.lambda$testDataBase64ImageMacPasteboard$0(MacPasteboardTest.java:89)

MacPasteboardTest > testNotAnImageURLMacPasteboard() FAILED
    java.lang.NullPointerException: Cannot invoke "com.sun.glass.ui.mac.MacPasteboardShim.pushMacPasteboard(java.util.HashMap)" because "test.com.sun.glass.ui.mac.MacPasteboardTest.macPasteboardShim" is null
        at test.com.sun.glass.ui.mac.MacPasteboardTest.lambda$testNotAnImageURLMacPasteboard$0(MacPasteboardTest.java:100)


The tests in this class assume we are running the Mac glass platform, so they should all be skipped when running the Headless glass platform. One way to do this would be to add a `PlatformUtil::isHeadless` method and change all of the `assumeTrue(PlatformUtil.isMac())` calls to `assumeTrue(PlatformUtil.isMac() && !PlatformUtil.isHeadless())`. The assumeTrue wouldn't be annotated with a bug ID, since this expresses a fundamental requirement of the test, not a bug that needs to be fixed.


2. ClipboardTest::testCopyUTF8String


ClipboardTest > testCopyUTF8String() FAILED
    org.opentest4j.AssertionFailedError: expected: < Jump to: 😃💁 Jump> but was: <HEADLESS_TEST>
        at app//org.junit.jupiter.api.AssertionFailureBuilder.build(AssertionFailureBuilder.java:151)
        at app//org.junit.jupiter.api.AssertionFailureBuilder.buildAndThrow(AssertionFailureBuilder.java:132)
        at app//org.junit.jupiter.api.AssertEquals.failNotEqual(AssertEquals.java:197)
        at app//org.junit.jupiter.api.AssertEquals.assertEquals(AssertEquals.java:182)
        at app//org.junit.jupiter.api.AssertEquals.assertEquals(AssertEquals.java:177)
        at app//org.junit.jupiter.api.Assertions.assertEquals(Assertions.java:1145)
        at app//test.javafx.scene.input.ClipboardTest.testCopyUTF8String(ClipboardTest.java:94)


This looks like a bug in the Headless glass platform code (not the test), so a bug tracking this headless clipboard failure should be filed. Then add `assumeTrue(!PlatformUtil.isHeadless())` along with a comment above the assumeTrue with the bug ID of the headless clipboard tracking bug.

Separately, another bug should be filed for the failing robot tests (I don't have a list, since I didn't run it with `-PUSE_ROBOT=true` for this test run).

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PR Comment: https://git.openjdk.org/jfx/pull/1836#issuecomment-3117871252