Add a regression test for FontMatrix right after ROS in a CFF Top DICT

src/test/java/org/verapdf/pd/font/cff/CFFCIDFontProgramTest.java

@@ -0,0 +1,97 @@
+/*
+ * This file is part of veraPDF Parser, a module of the veraPDF project.
+ * Copyright (c) 2015-2026, veraPDF Consortium <info@verapdf.org>
+ * All rights reserved.
+ *
+ * veraPDF Parser is free software: you can redistribute it and/or modify
+ * it under the terms of either:
+ *
+ * The GNU General public license GPLv3+.
+ * You should have received a copy of the GNU General Public License
+ * along with veraPDF Parser as the LICENSE.GPL file in the root of the source
+ * tree.  If not, see http://www.gnu.org/licenses/ or
+ * https://www.gnu.org/licenses/gpl-3.0.en.html.
+ *
+ * The Mozilla Public License MPLv2+.
+ * You should have received a copy of the Mozilla Public License along with
+ * veraPDF Parser as the LICENSE.MPL file in the root of the source tree.
+ * If a copy of the MPL was not distributed with this file, you can obtain one at
+ * http://mozilla.org/MPL/2.0/.
+ */
+package org.verapdf.pd.font.cff;
+
+import org.junit.Test;
+import org.verapdf.as.io.ASInputStream;
+import org.verapdf.io.InternalInputStream;
+import org.verapdf.tools.StaticResources;
+
+import java.io.IOException;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertTrue;
+
+/**
+ * Regression test for CID-keyed CFF Top DICT parsing.
+ * <p>
+ * Both fixtures are the same subset of Libertinus Serif (SIL OFL 1.1),
+ * embedded by Typst as a CIDFontType0 with an Identity charset (cid == gid).
+ * They differ only in Top DICT operator order:
+ * <ul>
+ *     <li>{@code LibertinusSerif-subset.cff}: ROS, Copyright, FontMatrix</li>
+ *     <li>{@code LibertinusSerif-subset-ros-fontmatrix.cff}: ROS, FontMatrix, Copyright</li>
+ * </ul>
+ * The second ordering used to make the parser pick up the ROS Registry SID
+ * (391) as FontMatrix[0], scaling every glyph width by 391000.
+ */
+public class CFFCIDFontProgramTest {
+
+    private static final String RESOURCE_DIR = "src/test/resources/org/verapdf/pd/font/cff/";
+    private static final String ROS_COPYRIGHT_FONTMATRIX = RESOURCE_DIR + "LibertinusSerif-subset.cff";
+    private static final String ROS_FONTMATRIX_COPYRIGHT = RESOURCE_DIR + "LibertinusSerif-subset-ros-fontmatrix.cff";
+
+    /**
+     * Advance widths from the /W array of the CIDFont dictionary the fixtures
+     * were embedded with, indexed by CID (== GID).
+     */
+    private static final float[] EXPECTED_WIDTHS = {
+            500, 730, 447, 264, 504, 250, 747, 372, 505.99997f, 220, 316, 390, 271,
+            542, 500, 541, 701, 485, 323, 695, 428, 310, 790, 457, 220
+    };
+
+    private static CFFCIDFontProgram parse(String path) throws IOException {
+        StaticResources.clear();
+        ASInputStream stream = new InternalInputStream(path, 2);
+        CFFFontProgram font = new CFFFontProgram(stream, null, true);
+        font.parseFont();
+        assertTrue(font.isCIDFont());
+        assertTrue(font.getFont() instanceof CFFCIDFontProgram);
+        return (CFFCIDFontProgram) font.getFont();
+    }
+
+    private static void assertWidthsMatchFontDictionary(CFFCIDFontProgram font) {
+        assertEquals(EXPECTED_WIDTHS.length, font.getNGlyphs());
+        for (int gid = 0; gid < EXPECTED_WIDTHS.length; ++gid) {
+            assertEquals("width of gid " + gid, EXPECTED_WIDTHS[gid], font.widths.getWidth(gid), 0.01f);
+        }
+    }
+
+    @Test
+    public void testWidthsWhenCopyrightSeparatesROSAndFontMatrix() throws IOException {
+        assertWidthsMatchFontDictionary(parse(ROS_COPYRIGHT_FONTMATRIX));
+    }
+
+    @Test
+    public void testWidthsWhenFontMatrixDirectlyFollowsROS() throws IOException {
+        assertWidthsMatchFontDictionary(parse(ROS_FONTMATRIX_COPYRIGHT));
+    }
+
+    @Test
+    public void testTopDictOperatorOrderDoesNotChangeWidths() throws IOException {
+        CFFCIDFontProgram a = parse(ROS_COPYRIGHT_FONTMATRIX);
+        CFFCIDFontProgram b = parse(ROS_FONTMATRIX_COPYRIGHT);
+        assertEquals(a.getNGlyphs(), b.getNGlyphs());
+        for (int gid = 0; gid < a.getNGlyphs(); ++gid) {
+            assertEquals("width of gid " + gid, a.widths.getWidth(gid), b.widths.getWidth(gid), 0f);
+        }
+    }
+}