8374804: ConditionalFeature media queries by mstr2 · Pull Request #2161 · openjdk/jfx

mstr2 · 2026-05-03T06:49:40Z

This PR adds the -fx-supports-conditional-feature media query, which allows applications to adapt their stylesheets to different platforms with varying conditional feature support. Currently, the built-in themes use hard-coded logic to include or exclude conditional-feature stylesheets. The new media query allows us to potentially remove the hard-coded logic in the future, and gives third-party themes an API to query conditional feature support.

I confirm that I make this contribution in accordance with the OpenJDK Interim AI Policy.

Progress

Change must not contain extraneous whitespace
Change requires CSR request JDK-8384139 to be approved
Commit message must refer to an issue
Change must be properly reviewed (2 reviews required, with at least 1 Reviewer, 1 Author)

Issues

JDK-8374804: ConditionalFeature media queries (Enhancement - P4)
JDK-8384139: ConditionalFeature media queries (CSR)

Reviewers

Andy Goryachev (@andy-goryachev-oracle - Reviewer)
Marius Hanl (@Maran23 - Committer)

Reviewing

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$ git checkout pull/2161

Update a local copy of the PR:
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$ git pull https://git.openjdk.org/jfx.git pull/2161/head

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$ git pr checkout 2161

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bridgekeeper · 2026-05-03T06:51:05Z

👋 Welcome back mstrauss! 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 · 2026-05-03T06:52:01Z

@mstr2 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:

8374804: ConditionalFeature media queries

Reviewed-by: angorya, mhanl

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 1 new commit pushed to the master branch:

b932758: 8386698: PlatformUtil has unused fields and methods

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openjdk · 2026-05-03T06:53:37Z

The total number of required reviews for this PR has been set to 2 based on the presence of this label: rfr. This can be overridden with the /reviewers command.

mstr2 · 2026-05-03T06:53:38Z

/reviewers 2

openjdk · 2026-05-03T06:54:02Z

@mstr2
The total number of required reviews for this PR (including the jcheck configuration and the last /reviewers command) is now set to 2 (with at least 1 Reviewer, 1 Author).

mlbridge · 2026-05-03T06:57:26Z

Webrevs

mstr2 · 2026-05-03T07:09:43Z

/csr

openjdk · 2026-05-03T07:12:05Z

@mstr2 has indicated that a compatibility and specification (CSR) request is needed for this pull request.

@mstr2 please create a CSR request for issue JDK-8374804 with the correct fix version. This pull request cannot be integrated until the CSR request is approved.

kevinrushforth · 2026-05-19T21:33:16Z

This looks like a nice addition. I'll review the CSR, but I hope others will review the code.

Reviewers: @andy-goryachev-oracle , ???

andy-goryachev-oracle · 2026-05-19T21:34:36Z

yes, it's in my review queue

andy-goryachev-oracle

Testing looks good. My feedback is mostly about documentation - I know it is very difficult to write docs from a new user perspective, especially since you know how the internals work in great detail.

andy-goryachev-oracle · 2026-05-21T18:25:08Z

            </tr>
            <tr>
-                <td class="value">-fx-prefers-persistent-scrollbars</td>
+                <td class="value nowrap">-fx-prefers-persistent-scrollbars</td>


just noticed this: why the -fx prefix is here but not in all the others?

In CSS, this is called a vendor prefix. It is used for all symbols that have not yet achieved what amounts to universal concensus. JavaFX uses vendor prefixes quite extensively; in fact, almost all styleable properties are vendor-prefixed (though not all: visibility and transition are standard-compliant and don't use a vendor prefix).

Most of the media features we support are standard-compliant, and you'll find that they also work exactly the same in other CSS applications like web browsers. However, -fx-prefers-persistent-scrollbars is not a standard feature; neither is -fx-supports-conditional-feature.

andy-goryachev-oracle · 2026-05-21T18:28:05Z

+            </tr>
+            <tr>
+                <td class="value nowrap">-fx-supports-conditional-feature</td>
+                <td class="value">


this cell looks way too busy. do you think it might be worth either extracting it into a dedicated table where each feature can be explained/described?

I've tried arranging the constants in several different ways, including a table-like vertical listing. However, that introduces huge amounts of whitespace that doesn't help readability either. I'm not too excited about adding descriptions to all of the constants; that information is only a click away now that we're linking to the Platform.isSupported(ConditionalFeature) method. I'd like to avoid duplicating normative specification (the CSS reference is a normative specification, not merely an informational document).

makes sense, especially since you've added the link.

andy-goryachev-oracle · 2026-05-21T18:28:36Z

+                    <span class="nowrap">input-touch</span> | <span class="nowrap">input-multitouch</span> |
+                    <span class="nowrap">input-pointer</span></td>
+                <td>discrete</td>
+                <td>Evaluates to <code>true</code> if <code>Platform.isSupported(ConditionalFeature)</code> returns


would it be better if this were a link to Platform.isSupported(ConditionalFeature) ?

Good idea, I've added the link.

andy-goryachev-oracle · 2026-05-21T18:34:46Z

+            }
+            """;
+
+        Stylesheet stylesheet = new CssParserShim().parseUnmerged(stylesheetText, true);


in the case of invalid conditional feature like

@media (-fx-supports-conditional-feature: xxx) { .button { -fx-background-color: red; } }

the CssParser writes to stderr - is that expected?
if so, should it be tested?

In general, I think that CssParser is one of the... let's call it least well-developed parts of JavaFX. Errors from MediaQueryParser are fed back into CssParser, where they are treated like all other errors. So that's not "new" code at work here.

Should the way CssParser reports errors be tested? Maybe, but then again, that time is better spent just discarding it entirely and replacing it with an implementation that's not as bad. In any case, it's out of scope for this PR because the changes here don't touch error reporting at all.

andy-goryachev-oracle · 2026-05-21T18:42:46Z

+                <td>discrete</td>
+                <td>Evaluates to <code>true</code> if <code>Platform.isSupported(ConditionalFeature)</code> returns
+                    <code>true</code> for the specified conditional feature.<br>This media feature cannot be
+                    evaluated in a boolean context.</td>


Could you please explain in more easily understandable terms that the "boolean context" means? Assume the reader is trying to use it for the first time.

Especially confusing because isSupported is a boolean...

I've added a link to the paragraph "Evaluating Media Features in a Boolean Context" which appears a bit earlier in the document.

perfect, thanks!

mstr2 · 2026-05-25T19:04:05Z

@Maran23 Do you want to to be the second reviewer?

Maran23 · 2026-05-25T20:47:19Z

@Maran23 Do you want to to be the second reviewer?

Yes! Will review and test in the coming days.

Maran23

Sorry for the delay. Changes look fine and work as expected.
Have 2 very minor suggestions.

Maran23 · 2026-06-17T17:37:45Z

        </figure>
-    <h5>Evaluating Media Features in a Boolean Context</h5>
+    <h5 id="mf-boolean-context">Evaluating Media Features in a Boolean Context</h5>
    <p>If the colon and value is omitted, the media feature is evaluated in a boolean context.


Already existing, but this should probably be:

Suggested change

<p>If the colon and value is omitted, the media feature is evaluated in a boolean context.

<p>If the colon and value are omitted, the media feature is evaluated in a boolean context.

We can also do that in a follow up, but IMO is close enough so fine for me to do here.

Maran23 · 2026-06-17T17:47:16Z

+        assertEquals(3, mediaRule.getQueries().size());
+
+        var expected = FunctionExpression.of("-fx-supports-conditional-feature", "scene3d", _ -> null, true);
+        var actual = mediaRule.getQueries().get(0);


Very minor: This can be getFirst() (and .get(2) could be getLast() below)

I usually only do this if I specifically only need the first (or last) element, but not when the code pattern repeats for subsequent elements (0, 1, 2 in this case).

kevinrushforth · 2026-06-18T19:37:56Z

This looks like a nice addition. I'll review the CSR, but I hope others will review the code.

I've reviewed the CSR. It is ready to be Finalized.

mstr2 · 2026-06-19T03:55:37Z

/integrate

openjdk · 2026-06-19T03:56:06Z

Going to push as commit 8020a85.
Since your change was applied there has been 1 commit pushed to the master branch:

b932758: 8386698: PlatformUtil has unused fields and methods

Your commit was automatically rebased without conflicts.

openjdk · 2026-06-19T03:56:13Z

@mstr2 Pushed as commit 8020a85.

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

ConditionalFeature media queries

f8ebff5

openjdk Bot added the rfr Ready for review label May 3, 2026

openjdk Bot added the csr Need approved CSR to integrate pull request label May 3, 2026

andy-goryachev-oracle reviewed May 21, 2026

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add doc links

507acb0

andy-goryachev-oracle approved these changes May 21, 2026

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Maran23 approved these changes Jun 17, 2026

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mstr2 added 2 commits June 17, 2026 22:12

cssref wording

0269ce5

Merge branch 'master' into feature/conditional-feature-query

2c8137d

mstr2 requested review from Maran23 and andy-goryachev-oracle June 17, 2026 20:15

andy-goryachev-oracle approved these changes Jun 17, 2026

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Maran23 approved these changes Jun 17, 2026

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openjdk Bot added ready Ready to be integrated and removed csr Need approved CSR to integrate pull request labels Jun 19, 2026

openjdk Bot added the integrated Pull request has been integrated label Jun 19, 2026

openjdk Bot closed this Jun 19, 2026

openjdk Bot removed ready Ready to be integrated rfr Ready for review labels Jun 19, 2026

Maran23 mentioned this pull request Jun 22, 2026

8374822: Platform media query #2193

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	<p>If the colon and value is omitted, the media feature is evaluated in a boolean context.
	<p>If the colon and value are omitted, the media feature is evaluated in a boolean context.

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