Add :is() and :where() selector support

styled-xml-parser/src/main/java/com/itextpdf/styledxmlparser/css/CommonCssConstants.java

@@ -1804,6 +1804,16 @@ public class CommonCssConstants {
      */
     public static final String HAS = "has";
 
+    /**
+     * The Constant IS.
+     */
+    public static final String IS = "is";
+
+    /**
+     * The Constant WHERE.
+     */
+    public static final String WHERE = "where";
+
     /**
      * The Constant DISABLED.
      */

styled-xml-parser/src/main/java/com/itextpdf/styledxmlparser/css/parse/CssSelectorParser.java

@@ -103,7 +103,7 @@ public static List<ICssSelectorItem> parseSelectorItems(String selector) {
      * @return a list of {@link ICssSelectorItem} objects representing the parsed components
      *         of the CSS selector
      */
-    static List<ICssSelectorItem> parseSelectorItems(String selector, boolean allowRelativeSelectorAtStart) {
+    public static List<ICssSelectorItem> parseSelectorItems(String selector, boolean allowRelativeSelectorAtStart) {
         List<ICssSelectorItem> selectorItems = new ArrayList<>();
         State state = new NoneState();
         for (int i = 0; i < selector.length(); ++i) {
@@ -140,7 +140,7 @@ static List<ICssSelectorItem> parseSelectorItems(String selector, boolean allowR
      * @param input the string to split
      * @return a list of string parts split by top-level commas
      */
-    static List<String> splitByTopLevelComma(String input) {
+    public static List<String> splitByTopLevelComma(String input) {
         return CssUtils.splitString(input, ',',
                 new EscapeGroup('(', ')'),
                 new EscapeGroup('"'),
@@ -503,6 +503,9 @@ private static abstract class FunctionState implements State {
         protected char closure;
         protected boolean inString = false;
         protected boolean isReadyForSwitch = false;
+        // Tracks nested parentheses for pseudo-class functions like :is(...), :not(...), :where(...), :has(...)
+        // Only used when closure == ')'.
+        protected int parenthesesDepth = 0;
 
         /**
          * Constructs a new FunctionState object with the specified closure character.
@@ -533,7 +536,27 @@ public void addChar(char c, boolean isEscaped) {
             if ((c == '"' || c == '\'') && !isEscaped) {
                 inString = !inString;
             }
-            if (c == closure && !isEscaped && !inString) {
+
+            if (isEscaped || inString) {
+                return;
+            }
+
+            if (closure == ')') {
+                if (c == '(') {
+                    parenthesesDepth++;
+                } else if (c == ')') {
+                    // Close one nesting level; function ends when we close the initial '('.
+                    if (parenthesesDepth > 0) {
+                        parenthesesDepth--;
+                    }
+                    if (parenthesesDepth == 0) {
+                        isReadyForSwitch = true;
+                    }
+                }
+                return;
+            }
+
+            if (c == closure) {
                 isReadyForSwitch = true;
             }
         }

styled-xml-parser/src/main/java/com/itextpdf/styledxmlparser/css/selector/item/CssPseudoClassForgivingSelectorListSelectorItem.java

@@ -0,0 +1,116 @@
+/*
+    This file is part of the iText (R) project.
+    Copyright (c) 1998-2026 Apryse Group NV
+    Authors: Apryse Software.
+
+    This program is offered under a commercial and under the AGPL license.
+    For commercial licensing, contact us at https://itextpdf.com/sales.  For AGPL licensing, see below.
+
+    AGPL licensing:
+    This program is free software: you can redistribute it and/or modify
+    it under the terms of the GNU Affero General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    This program 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 Affero General Public License for more details.
+
+    You should have received a copy of the GNU Affero General Public License
+    along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+package com.itextpdf.styledxmlparser.css.selector.item;
+
+import com.itextpdf.styledxmlparser.css.parse.CssSelectorParser;
+import com.itextpdf.styledxmlparser.css.selector.CssSelector;
+import com.itextpdf.styledxmlparser.css.selector.ICssSelector;
+import com.itextpdf.styledxmlparser.node.ICustomElementNode;
+import com.itextpdf.styledxmlparser.node.IDocumentNode;
+import com.itextpdf.styledxmlparser.node.IElementNode;
+import com.itextpdf.styledxmlparser.node.INode;
+
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.List;
+
+/**
+ * Base class for pseudo-classes that accept a forgiving selector list (e.g. :is(), :where()).
+ */
+abstract class CssPseudoClassForgivingSelectorListSelectorItem extends CssPseudoClassSelectorItem {
+    protected final List<ICssSelector> selectorList;
+
+    protected CssPseudoClassForgivingSelectorListSelectorItem(String pseudoClass, List<ICssSelector> selectorList,
+                                                              String argumentsString) {
+        super(pseudoClass, argumentsString);
+        this.selectorList = selectorList;
+    }
+
+    @Override
+    public boolean matches(INode node) {
+        if (!(node instanceof IElementNode) || node instanceof ICustomElementNode || node instanceof IDocumentNode) {
+            return false;
+        }
+        for (ICssSelector sel : selectorList) {
+            if (sel != null && sel.matches(node)) {
+                return true;
+            }
+        }
+        return false;
+    }
+
+    /**
+     * Parses a forgiving selector list for :is() / :where().
+     * <p>
+     * Per Selectors Level 4, :is() and :where() accept a forgiving selector list:
+     * invalid selectors are ignored rather than invalidating the whole pseudo-class.
+     *
+     * @param arguments selector list as written inside parentheses
+     * @return list of valid selectors (possibly empty), or null if arguments are syntactically missing
+     */
+    static List<ICssSelector> parseForgivingSelectorListWithoutPseudoElements(String arguments) {
+        if (arguments == null || arguments.trim().isEmpty()) {
+            // :is() / :where() with empty arguments is invalid.
+            return null;
+        }
+
+        List<String> parts = CssSelectorParser.splitByTopLevelComma(arguments);
+        if (parts.isEmpty()) {
+            return null;
+        }
+
+        List<ICssSelector> selectors = new ArrayList<>();
+        for (String rawPart : parts) {
+            String part = rawPart == null ? "" : rawPart.trim();
+            if (part.isEmpty()) {
+                // Empty entries like :is(.a,,.b) are invalid selectors in the list; ignore (forgiving).
+                continue;
+            }
+
+            try {
+                CssSelector sel = new CssSelector(CssSelectorParser.parseSelectorItems(part, false));
+                if (!containsPseudoElement(Collections.singletonList(sel))) {
+                    selectors.add(sel);
+                }
+            } catch (IllegalArgumentException ex) {
+                // Invalid/unsupported selector in the list; ignore (forgiving).
+            }
+        }
+
+        return selectors;
+    }
+
+    static boolean containsPseudoElement(List<ICssSelector> selectors) {
+        for (ICssSelector sel : selectors) {
+            if (sel instanceof CssSelector) {
+                for (ICssSelectorItem item : ((CssSelector) sel).getSelectorItems()) {
+                    if (item instanceof CssPseudoElementSelectorItem) {
+                        return true;
+                    }
+                }
+            }
+        }
+        return false;
+    }
+}

styled-xml-parser/src/main/java/com/itextpdf/styledxmlparser/css/selector/item/CssPseudoClassIsSelectorItem.java

@@ -0,0 +1,33 @@
+package com.itextpdf.styledxmlparser.css.selector.item;
+
+import com.itextpdf.styledxmlparser.css.CommonCssConstants;
+import com.itextpdf.styledxmlparser.css.selector.ICssSelector;
+
+import java.util.List;
+
+class CssPseudoClassIsSelectorItem extends CssPseudoClassForgivingSelectorListSelectorItem {
+
+    CssPseudoClassIsSelectorItem(List<ICssSelector> selectorList, String argumentsString) {
+        super(CommonCssConstants.IS, selectorList, argumentsString);
+    }
+
+    @Override
+    public int getSpecificity() {
+        int max = 0;
+        for (ICssSelector sel : selectorList) {
+            if (sel != null) {
+                max = Math.max(max, sel.calculateSpecificity());
+            }
+        }
+        return max;
+    }
+
+    public static CssPseudoClassIsSelectorItem createIsSelectorItem(String arguments) {
+        List<ICssSelector> selectors = parseForgivingSelectorListWithoutPseudoElements(arguments);
+        if (selectors == null) {
+            return null;
+        }
+        return new CssPseudoClassIsSelectorItem(selectors, arguments);
+    }
+}
+

styled-xml-parser/src/main/java/com/itextpdf/styledxmlparser/css/selector/item/CssPseudoClassNotSelectorItem.java

@@ -41,6 +41,13 @@ class CssPseudoClassNotSelectorItem extends CssPseudoClassSelectorItem {
         this.argumentsSelector = argumentsSelector;
     }
 
+    @Override
+    public int getSpecificity() {
+        // Per Selectors Level 4: :not() specificity is replaced by the specificity
+        // of the most specific complex selector in its selector list argument.
+        return argumentsSelector != null ? argumentsSelector.calculateSpecificity() : 0;
+    }
+
     public List<ICssSelectorItem> getArgumentsSelector() {
         return CssSelectorParser.parseSelectorItems(arguments);
     }

styled-xml-parser/src/main/java/com/itextpdf/styledxmlparser/css/selector/item/CssPseudoClassSelectorItem.java

@@ -119,6 +119,10 @@ public static CssPseudoClassSelectorItem create(String pseudoClass, String argum
                 return createHasSelectorItem(arguments);
             case CommonCssConstants.NOT:
                 return createNotSelectorItem(arguments);
+            case CommonCssConstants.IS:
+                return CssPseudoClassIsSelectorItem.createIsSelectorItem(arguments);
+            case CommonCssConstants.WHERE:
+                return CssPseudoClassWhereSelectorItem.createWhereSelectorItem(arguments);
             case CommonCssConstants.ROOT:
                 return CssPseudoClassRootSelectorItem.getInstance();
             case CommonCssConstants.LINK:

styled-xml-parser/src/main/java/com/itextpdf/styledxmlparser/css/selector/item/CssPseudoClassWhereSelectorItem.java

@@ -0,0 +1,28 @@
+package com.itextpdf.styledxmlparser.css.selector.item;
+
+import com.itextpdf.styledxmlparser.css.CommonCssConstants;
+import com.itextpdf.styledxmlparser.css.selector.ICssSelector;
+
+import java.util.List;
+
+class CssPseudoClassWhereSelectorItem extends CssPseudoClassForgivingSelectorListSelectorItem {
+
+    CssPseudoClassWhereSelectorItem(List<ICssSelector> selectorList, String argumentsString) {
+        super(CommonCssConstants.WHERE, selectorList, argumentsString);
+    }
+
+    @Override
+    public int getSpecificity() {
+        // Per Selectors Level 4: :where() always contributes 0 specificity.
+        return 0;
+    }
+
+    public static CssPseudoClassWhereSelectorItem createWhereSelectorItem(String arguments) {
+        List<ICssSelector> selectors = parseForgivingSelectorListWithoutPseudoElements(arguments);
+        if (selectors == null) {
+            return null;
+        }
+        return new CssPseudoClassWhereSelectorItem(selectors, arguments);
+    }
+}
+