8364149: Conditional stylesheet imports

modules/javafx.graphics/src/main/docs/javafx/scene/doc-files/cssref.html

@@ -781,15 +781,14 @@ <h4>Example</h4>
     </p>
 
     <h3><a id="introatrules">&#64; Rules</a></h3>
-    <h4>@import</h4>
-    <p>
-        Beginning with JavaFX 8u20, the CSS
-        <a href="http://www.w3.org/TR/CSS21/cascade.html#at-import">@import</a> is partially supported.
-        Only unconditional import is supported. In other words, the media&#8209;type qualifier is not supported.
-        Also, the JavaFX CSS parser is non-compliant with regard to where an @import may appear within a stylesheet
-        (see <a href="http://www.w3.org/TR/CSS21/syndata.html#at-rules">At&#8209;rules</a>).
-        Users are cautioned that this will be fixed in a future release. Adherence to the W3C standard is strongly advised.
-    </p>
+    <h4>@import <a class="grammar" style="font-weight: normal">[ &lt;url&gt; | &lt;string&gt; ] &lt;media-query-list&gt;? ;</a></h4>
+    <p>The @import rule allows applications to import rules from other stylesheets. Import rules must be placed before
+        all other @-rules and style rules, and no other rule can be placed between @import rules. If a valid import
+        rule is encountered, the content of the referenced stylesheet is treated as if it literally appeared at the
+        location of the @import rule.</p>
+    <p>An import rule can optionally include a <a href="#figure-media-query-list">media query list</a> that specifies
+        the conditions under which the imported rules apply, as if they were wrapped in a @media rule with the same
+        media query list.</p>
     <h4>@font-face</h4>
     <p>Since JavaFX 8, the implementation partially supports the CSS3 syntax to load a font from a URL using the
     <a href="http://www.w3.org/TR/css3-fonts/#the-font-face-rule">@font&#8209;face</a> rule:</p>
@@ -839,7 +838,7 @@ <h4>@media</h4>
         A media query list evaluates to <code>true</code> if <em>any</em> of the media queries is <code>true</code>,
         and evaluates to <code>false</code> only if <em>all</em> the media queries are <code>false</code>.
         An empty media query list evaluates to <code>true</code>.
-        <figure style="margin: 0">
+        <figure style="margin: 0" id="figure-media-query-list">
             <img src="media-query.svg" width="210" alt="Media Query List">
             <figcaption style="float: left; margin-top: 27px">
                 <span class="grammar">&lt;media-query-list&gt;:</span>

modules/javafx.graphics/src/main/java/com/sun/javafx/css/media/MediaFeatures.java

@@ -31,15 +31,21 @@
 import com.sun.javafx.css.parser.Token;
 import javafx.application.ColorScheme;
 import java.util.Locale;
+import java.util.function.BiFunction;
 import java.util.function.Function;
 
 /**
  * Contains the implementations of all supported media feature queries.
  */
-final class MediaFeatures {
+public final class MediaFeatures {
 
     private MediaFeatures() {}
 
+    // Extension point for unit tests to add media features
+    public static BiFunction<String, Token, MediaQuery> DEFAULT = (featureName, _) -> {
+        throw new IllegalArgumentException(String.format("Unknown media feature <%s>", featureName));
+    };
+
     /**
      * Returns a {@code MediaQuery} that evaluates the specified feature in a discrete context.
      *
@@ -132,8 +138,7 @@ lowerCaseFeatureName, lowerCaseTextValue(featureValue),
             case "-fx-prefers-persistent-scrollbars" -> booleanPreferenceExpression(
                 lowerCaseFeatureName, featureValue, "persistent", MediaQueryContext::isPersistentScrollBars);
 
-            default -> throw new IllegalArgumentException(
-                String.format("Unknown media feature <%s>", featureName));
+            default -> DEFAULT.apply(featureName, featureValue);
         };
     }
 

modules/javafx.graphics/src/main/java/com/sun/javafx/css/media/MediaQuery.java

@@ -54,6 +54,16 @@ public sealed interface MediaQuery
      */
     int getContextAwareness();
 
+    /**
+     * Attempts to determine the result of this media query without a context, and returns {@link TriState#TRUE}
+     * if the query matches for all possible contexts, {@link TriState#FALSE} if it matches for no possible
+     * context, or {@link TriState#UNKNOWN} if the result depends on the context or cannot be determined.
+     *
+     * @return {@link TriState#TRUE} if the query is always true, {@link TriState#FALSE}
+     *         if the query is always false, otherwise {@link TriState#UNKNOWN}
+     */
+    TriState evaluate();
+
     /**
      * Evaluates this media query against the provided context.
      *

modules/javafx.graphics/src/main/java/com/sun/javafx/css/media/MediaQueryList.java

@@ -0,0 +1,111 @@
+/*
+ * Copyright (c) 2026, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.  Oracle designates this
+ * particular file as subject to the "Classpath" exception as provided
+ * by Oracle in the LICENSE file that accompanied this code.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+package com.sun.javafx.css.media;
+
+import javafx.css.StyleConverter;
+import java.io.DataInputStream;
+import java.io.DataOutputStream;
+import java.io.IOException;
+import java.util.ArrayList;
+
+public final class MediaQueryList extends ArrayList<MediaQuery> {
+
+    public MediaQueryList() {}
+
+    public MediaQueryList(int capacity) {
+        super(capacity);
+    }
+
+    /**
+     * Attempts to determine the result of this media query list without a context, and returns
+     * {@link TriState#TRUE} if it matches for all possible contexts, {@link TriState#FALSE} if
+     * it matches for no possible context, or {@link TriState#UNKNOWN} if the result depends on
+     * the context or cannot be determined.
+     *
+     * @return {@link TriState#TRUE} if the media query list is always true, {@link TriState#FALSE}
+     *         if the media query list is always false, otherwise {@link TriState#UNKNOWN}
+     */
+    public TriState evaluate() {
+        if (isEmpty()) {
+            return TriState.TRUE;
+        }
+
+        boolean unknown = false;
+
+        for (int i = 0, max = size(); i < max; i++) {
+            switch (get(i).evaluate()) {
+                case TRUE -> { return TriState.TRUE; }
+                case UNKNOWN -> unknown = true;
+            }
+        }
+
+        return unknown ? TriState.UNKNOWN : TriState.FALSE;
+    }
+
+    /**
+     * Evaluates whether any of the media queries is {@code true}.
+     *
+     * @param context the evaluation context
+     * @return {@code true} if any of the media queries is {@code true} or if the list is empty,
+     *         {@code false} otherwise
+     */
+    public boolean evaluate(MediaQueryContext context) {
+        if (isEmpty()) {
+            return true;
+        }
+
+        for (int i = 0, max = size(); i < max; i++) {
+            MediaQuery query = get(i);
+            boolean value = query.evaluate(context);
+            context.notifyQueryEvaluated(query, value);
+
+            if (value) {
+                return true;
+            }
+        }
+
+        return false;
+    }
+
+    public void writeBinary(DataOutputStream stream, StyleConverter.StringStore stringStore) throws IOException {
+        stream.writeInt(size());
+
+        for (MediaQuery query : this) {
+            MediaQuerySerializer.writeBinary(query, stream, stringStore);
+        }
+    }
+
+    public static MediaQueryList readBinary(DataInputStream stream, String[] strings) throws IOException {
+        int size = stream.readInt();
+        var queries = new MediaQueryList(size);
+
+        for (int i = 0; i < size; i++) {
+            queries.add(MediaQuerySerializer.readBinary(stream, strings));
+        }
+
+        return queries;
+    }
+}

modules/javafx.graphics/src/main/java/com/sun/javafx/css/media/MediaQueryParser.java

@@ -83,11 +83,11 @@ public MediaQueryParser(BiConsumer<Token, String> errorHandler) {
      * }</pre>
      *
      * @param tokens the token stream
-     * @return the expression
+     * @return the media query list
      */
-    public List<MediaQuery> parseMediaQueryList(List<Token> tokens) {
+    public MediaQueryList parseMediaQueryList(List<Token> tokens) {
         var stream = new TokenStream(tokens);
-        var expressions = new ArrayList<MediaQuery>();
+        var expressions = new MediaQueryList();
         boolean lastWasComma = false;
 
         while (stream.consume() != null) {

modules/javafx.graphics/src/main/java/com/sun/javafx/css/media/MediaRule.java

@@ -30,28 +30,27 @@
 import java.io.DataInputStream;
 import java.io.DataOutputStream;
 import java.io.IOException;
-import java.util.List;
 
 /**
  * CSS media rules are @-rules that contain media queries. A media query tests the "external"
  * configuration of a {@link Scene}, and is independent of its scene graph content.
  */
 public final class MediaRule {
 
-    private final List<MediaQuery> queries;
+    private final MediaQueryList queries;
     private final MediaRule parent;
 
-    public MediaRule(List<MediaQuery> queries, MediaRule parent) {
-        this.queries = List.copyOf(queries);
+    public MediaRule(MediaQueryList queries, MediaRule parent) {
+        this.queries = queries;
         this.parent = parent;
     }
 
     /**
-     * Returns the unmodifiable list of media queries.
+     * Returns the list of media queries.
      *
-     * @return the unmodifiable list of media queries
+     * @return the list of media queries
      */
-    public List<MediaQuery> getQueries() {
+    public MediaQueryList getQueries() {
         return queries;
     }
 
@@ -64,6 +63,31 @@ public MediaRule getParent() {
         return parent;
     }
 
+    /**
+     * Attempts to determine the result of this media rule without a context, and returns {@link TriState#TRUE}
+     * if the rule matches for all possible contexts, {@link TriState#FALSE} if it matches for no possible
+     * context, or {@link TriState#UNKNOWN} if the result depends on the context or cannot be determined.
+     *
+     * @return {@link TriState#TRUE} if the rule always matches, {@link TriState#FALSE}
+     *         if the rule never matches, otherwise {@link TriState#UNKNOWN}
+     */
+    public TriState evaluate() {
+        boolean parentUnknown = false;
+
+        if (parent != null) {
+            switch (parent.evaluate()) {
+                case FALSE -> { return TriState.FALSE; }
+                case UNKNOWN -> parentUnknown = true;
+            }
+        }
+
+        return switch (queries.evaluate()) {
+            case TRUE -> parentUnknown ? TriState.UNKNOWN : TriState.TRUE;
+            case FALSE -> TriState.FALSE;
+            case UNKNOWN -> TriState.UNKNOWN;
+        };
+    }
+
     /**
      * Evaluates whether any of the media queries is {@code true}.
      *
@@ -76,29 +100,11 @@ public boolean evaluate(MediaQueryContext context) {
             return false;
         }
 
-        if (queries.isEmpty()) {
-            return true;
-        }
-
-        for (int i = 0, max = queries.size(); i < max; i++) {
-            MediaQuery query = queries.get(i);
-            boolean value = query.evaluate(context);
-            context.notifyQueryEvaluated(query, value);
-
-            if (value) {
-                return true;
-            }
-        }
-
-        return false;
+        return queries.evaluate(context);
     }
 
     public void writeBinary(DataOutputStream stream, StyleConverter.StringStore stringStore) throws IOException {
-        stream.writeInt(queries.size());
-
-        for (MediaQuery query : queries) {
-            MediaQuerySerializer.writeBinary(query, stream, stringStore);
-        }
+        queries.writeBinary(stream, stringStore);
 
         stream.writeBoolean(parent != null);
 
@@ -108,16 +114,11 @@ public void writeBinary(DataOutputStream stream, StyleConverter.StringStore stri
     }
 
     public static MediaRule readBinary(DataInputStream stream, String[] strings) throws IOException {
-        int size = stream.readInt();
-        var queries = new MediaQuery[size];
-
-        for (int i = 0; i < size; i++) {
-            queries[i] = MediaQuerySerializer.readBinary(stream, strings);
-        }
+        MediaQueryList queries = MediaQueryList.readBinary(stream, strings);
 
         boolean hasParent = stream.readBoolean();
         MediaRule parentRule = hasParent ? readBinary(stream, strings) : null;
 
-        return new MediaRule(List.of(queries), parentRule);
+        return new MediaRule(queries, parentRule);
     }
 }

modules/javafx.graphics/src/main/java/com/sun/javafx/css/media/TriState.java

@@ -0,0 +1,32 @@
+/*
+ * Copyright (c) 2026, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.  Oracle designates this
+ * particular file as subject to the "Classpath" exception as provided
+ * by Oracle in the LICENSE file that accompanied this code.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+package com.sun.javafx.css.media;
+
+public enum TriState {
+    TRUE,
+    FALSE,
+    UNKNOWN
+}