PDFBOX-6292: don't derive the space width from a substitute's encoding

pdfbox/src/main/java/org/apache/pdfbox/pdmodel/font/PDFont.java

@@ -575,6 +575,17 @@ public Matrix getFontMatrix()
         return DEFAULT_FONT_MATRIX;
     }
 
+    /**
+     * Whether {@link #encode(int)} derives codes from a substitute font program rather than from
+     * this font's encoding, so that the codes need not exist in the PDF.
+     *
+     * @return true if encoded codes depend on the installed substitute
+     */
+    protected boolean isEncodedViaSubstitute()
+    {
+        return false;
+    }
+
     /**
      * Determines the width of the space character. This is very important for text extraction.
      *
@@ -596,16 +607,19 @@ public float getSpaceWidth()
                 }
                 else
                 {
-                    try
+                    if (!isEncodedViaSubstitute())
                     {
-                        // PDFBOX-5920: try with encoding, which gets the correct code
-                        fontWidthOfSpace = getStringWidth(" ");
-                    }
-                    catch (IllegalArgumentException | UnsupportedOperationException ex)
-                    {
-                        // Happens if space is not available in the font
-                        // or if encoding isn't implemented
-                        LOG.debug(ex.getMessage(), ex);
+                        try
+                        {
+                            // PDFBOX-5920: try with encoding, which gets the correct code
+                            fontWidthOfSpace = getStringWidth(" ");
+                        }
+                        catch (IllegalArgumentException | UnsupportedOperationException ex)
+                        {
+                            // Happens if space is not available in the font
+                            // or if encoding isn't implemented
+                            LOG.debug(ex.getMessage(), ex);
+                        }
                     }
                     if (fontWidthOfSpace <= 0)
                     {

pdfbox/src/main/java/org/apache/pdfbox/pdmodel/font/PDType0Font.java

@@ -561,6 +561,15 @@ public float getWidthFromFont(int code) throws IOException
         return descendantFont.getWidthFromFont(code, this);
     }
 
+    @Override
+    protected boolean isEncodedViaSubstitute()
+    {
+        // Identity CMap without ToUnicode: encode() returns the substitute's GIDs (PDFBOX-6292)
+        return !isEmbedded() && descendantFont instanceof PDCIDFontType2 &&
+                cMap != null && cMap.getName() != null && cMap.getName().startsWith("Identity-") &&
+                !getCOSObject().containsKey(COSName.TO_UNICODE);
+    }
+
     @Override
     public boolean isEmbedded()
     {

pdfbox/src/test/java/org/apache/pdfbox/pdmodel/font/SubstituteSpaceWidthTest.java

@@ -0,0 +1,106 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.pdfbox.pdmodel.font;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assumptions.assumeTrue;
+
+import java.io.IOException;
+
+import org.apache.pdfbox.cos.COSArray;
+import org.apache.pdfbox.cos.COSDictionary;
+import org.apache.pdfbox.cos.COSInteger;
+import org.apache.pdfbox.cos.COSName;
+import org.apache.pdfbox.cos.COSString;
+import org.junit.jupiter.api.Test;
+
+/**
+ * The space width of a non-embedded Identity-H CIDFontType2 without ToUnicode must come from the
+ * PDF, not from whichever substitute is installed. PDFBOX-6292.
+ */
+class SubstituteSpaceWidthTest
+{
+    @Test
+    void testSpaceWidthIndependentOfSubstitute() throws IOException
+    {
+        PDType0Font font = new PDType0Font(simSunIdentityH(), null);
+        PDCIDFontType2 cidFont = (PDCIDFontType2) font.getDescendantFont();
+        // any substitute works, down to the bundled last-resort font, as long as its space GID
+        // lands in the /W range below
+        int substituteSpaceGid = cidFont.getTrueTypeFont().getUnicodeCmapLookup().getGlyphId(' ');
+        assumeTrue(substituteSpaceGid > 0 && substituteSpaceGid < 32,
+                "substitute's space GID outside the test's /W range");
+
+        // an Identity CMap without ToUnicode says nothing about which code is a space; the answer
+        // must not depend on which substitute happens to be installed
+        assertEquals(font.getWidth(32), font.getSpaceWidth());
+    }
+
+    private static COSDictionary simSunIdentityH()
+    {
+        COSDictionary ros = new COSDictionary();
+        ros.setItem(COSName.REGISTRY, new COSString("Adobe"));
+        ros.setItem(COSName.ORDERING, new COSString("GB1"));
+        ros.setInt(COSName.SUPPLEMENT, 2);
+
+        COSDictionary fd = new COSDictionary();
+        fd.setItem(COSName.TYPE, COSName.FONT_DESC);
+        fd.setName(COSName.FONT_NAME, "SimSun");
+        fd.setInt(COSName.FLAGS, 6);
+        COSArray bbox = new COSArray();
+        bbox.add(COSInteger.get(0));
+        bbox.add(COSInteger.get(-141));
+        bbox.add(COSInteger.get(996));
+        bbox.add(COSInteger.get(855));
+        fd.setItem(COSName.FONT_BBOX, bbox);
+        fd.setInt(COSName.ITALIC_ANGLE, 0);
+        fd.setInt(COSName.ASCENT, 859);
+        fd.setInt(COSName.DESCENT, -141);
+        fd.setInt(COSName.CAP_HEIGHT, 859);
+        fd.setInt(COSName.STEM_V, 80);
+
+        // widths for codes 0-31 only: the substitute's space GID lands here if it is wrongly
+        // used as a code, while the PDF's code 32 falls back to /DW
+        COSArray widths = new COSArray();
+        for (int i = 0; i < 32; i++)
+        {
+            widths.add(COSInteger.get(500));
+        }
+        COSArray w = new COSArray();
+        w.add(COSInteger.get(0));
+        w.add(widths);
+
+        COSDictionary cid = new COSDictionary();
+        cid.setItem(COSName.TYPE, COSName.FONT);
+        cid.setItem(COSName.SUBTYPE, COSName.CID_FONT_TYPE2);
+        cid.setName(COSName.BASE_FONT, "SimSun");
+        cid.setItem(COSName.CIDSYSTEMINFO, ros);
+        cid.setItem(COSName.FONT_DESC, fd);
+        cid.setInt(COSName.DW, 1000);
+        cid.setItem(COSName.W, w);
+
+        COSArray descendants = new COSArray();
+        descendants.add(cid);
+        COSDictionary type0 = new COSDictionary();
+        type0.setItem(COSName.TYPE, COSName.FONT);
+        type0.setItem(COSName.SUBTYPE, COSName.TYPE0);
+        type0.setName(COSName.BASE_FONT, "SimSun");
+        type0.setName(COSName.ENCODING, "Identity-H");
+        type0.setItem(COSName.DESCENDANT_FONTS, descendants);
+        return type0;
+    }
+}