Stop throwing NPE on Type3 char proc metrics when no glyph bbox is declared

src/main/java/org/verapdf/pd/font/type3/PDType3Font.java

@@ -163,7 +163,7 @@ public Double getAscentFromProgram(int code) {
         if (charProc.getType() == COSObjType.COS_STREAM) {
             try (Type3CharProcParser parser = new Type3CharProcParser(charProc.getData(COSStream.FilterFlags.DECODE))) {
                 parser.parse();
-                return parser.getAscent();
+                return parser.getAscentOrNull();
             } catch (IOException e) {
                 LOGGER.log(Level.FINE, "Can't get ascent from type 3 char proc");
             }
@@ -176,7 +176,7 @@ public Double getDescentFromProgram(int code) {
         if (charProc.getType() == COSObjType.COS_STREAM) {
             try (Type3CharProcParser parser = new Type3CharProcParser(charProc.getData(COSStream.FilterFlags.DECODE))) {
                 parser.parse();
-                return parser.getDescent();
+                return parser.getDescentOrNull();
             } catch (IOException e) {
                 LOGGER.log(Level.FINE, "Can't get descent from type 3 char proc");
             }

src/main/java/org/verapdf/pd/font/type3/Type3CharProcParser.java

@@ -92,11 +92,45 @@ public double getWidth() {
         return width;
     }
 
+    /**
+     * @return ascent of the glyph presented by given char proc, or 0 if the char
+     * proc declares no glyph bounding box.
+     * @deprecated a char proc that begins with the d0 operator specifies the
+     * glyph width only (ISO 32000-1, 9.6.5.3) and declares no glyph bounding
+     * box, so its ascent is undefined rather than 0. This method cannot express
+     * that; use {@link #getAscentOrNull()} instead.
+     */
+    @Deprecated
     public double getAscent() {
-        return ascent;
+        return ascent == null ? 0 : ascent;
     }
 
+    /**
+     * @return descent of the glyph presented by given char proc, or 0 if the
+     * char proc declares no glyph bounding box.
+     * @deprecated undefined descent cannot be distinguished from 0; use
+     * {@link #getDescentOrNull()} instead. See {@link #getAscent()}.
+     */
+    @Deprecated
     public double getDescent() {
+        return descent == null ? 0 : descent;
+    }
+
+    /**
+     * @return ascent of the glyph presented by given char proc, or null if the
+     * char proc declares no glyph bounding box. A char proc that begins with
+     * the d0 operator specifies the glyph width only (ISO 32000-1, 9.6.5.3),
+     * so its ascent is undefined rather than 0.
+     */
+    public Double getAscentOrNull() {
+        return ascent;
+    }
+
+    /**
+     * @return descent of the glyph presented by given char proc, or null if the
+     * char proc declares no glyph bounding box. See {@link #getAscentOrNull()}.
+     */
+    public Double getDescentOrNull() {
         return descent;
     }
 }

src/test/java/org/verapdf/pd/font/type3/Type3CharProcParserTest.java

@@ -0,0 +1,102 @@
+/*
+ * 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.type3;
+
+import org.junit.jupiter.api.Assertions;
+import org.junit.jupiter.api.Test;
+import org.verapdf.as.io.ASMemoryInStream;
+
+import java.io.IOException;
+import java.nio.charset.StandardCharsets;
+
+class Type3CharProcParserTest {
+
+    private static final double EPSILON = 1.0e-6;
+
+    private static Type3CharProcParser parse(String charProc) throws IOException {
+        Type3CharProcParser parser = new Type3CharProcParser(
+                new ASMemoryInStream(charProc.getBytes(StandardCharsets.ISO_8859_1)));
+        parser.parse();
+        return parser;
+    }
+
+    /**
+     * A char proc that starts with d1 declares a glyph bounding box, so both
+     * metrics are available.
+     */
+    @Test
+    void d1CharProcReportsMetrics() throws IOException {
+        try (Type3CharProcParser parser = parse("1000 0 0 -200 750 800 d1\n")) {
+            Assertions.assertEquals(1000, parser.getWidth(), EPSILON);
+            Assertions.assertEquals(800, parser.getAscentOrNull(), EPSILON);
+            Assertions.assertEquals(-200, parser.getDescentOrNull(), EPSILON);
+        }
+    }
+
+    /**
+     * A char proc that starts with d0 specifies the glyph width only
+     * (ISO 32000-1, 9.6.5.3). Its ascent and descent are undefined, so they
+     * must be reported as null rather than defaulted to zero: a zero descent
+     * would win a minimum comparison against the real descents of the other
+     * glyphs in the same font.
+     */
+    @Test
+    void d0CharProcReportsNullMetrics() throws IOException {
+        try (Type3CharProcParser parser = parse("1000 0 d0\n")) {
+            Assertions.assertEquals(1000, parser.getWidth(), EPSILON);
+            Assertions.assertNull(parser.getAscentOrNull());
+            Assertions.assertNull(parser.getDescentOrNull());
+        }
+    }
+
+    /**
+     * The pre-existing primitive getters keep their released signatures and
+     * substitute 0 for an undefined metric instead of throwing.
+     */
+    @Test
+    @SuppressWarnings("deprecation")
+    void deprecatedPrimitiveGettersSubstituteZeroForUndefinedMetrics() throws IOException {
+        try (Type3CharProcParser parser = parse("1000 0 d0\n")) {
+            Assertions.assertEquals(0, parser.getAscent(), EPSILON);
+            Assertions.assertEquals(0, parser.getDescent(), EPSILON);
+        }
+        try (Type3CharProcParser parser = parse("1000 0 0 -200 750 800 d1\n")) {
+            Assertions.assertEquals(800, parser.getAscent(), EPSILON);
+            Assertions.assertEquals(-200, parser.getDescent(), EPSILON);
+        }
+    }
+
+    /**
+     * A char proc whose bounding box is not terminated by d1 is corrupted;
+     * parse() reports it and leaves no metrics behind.
+     */
+    @Test
+    void corruptedCharProcThrowsAndClearsMetrics() throws IOException {
+        Type3CharProcParser parser = new Type3CharProcParser(
+                new ASMemoryInStream("1000 0 0 -200 750 800 xx\n".getBytes(StandardCharsets.ISO_8859_1)));
+        try (Type3CharProcParser closeable = parser) {
+            Assertions.assertThrows(IOException.class, closeable::parse);
+        }
+        Assertions.assertEquals(-1, parser.getWidth(), EPSILON);
+        Assertions.assertNull(parser.getAscentOrNull());
+        Assertions.assertNull(parser.getDescentOrNull());
+    }
+}