Generate a PDF/A compliant CIDSet instead of using hardcoded FFFFFFFFC0

lib/font/embedded.js

@@ -181,9 +181,15 @@ class EmbeddedFont extends PDFFont {
     }
 
     if (this.document.subset && this.document.subset === 1) {
-      const CIDSet = Buffer.from('FFFFFFFFC0', 'hex');
+      const maxCID = this.widths.length - 1;
+      const cidSetBuffer = Buffer.alloc(Math.ceil((maxCID + 1) / 8), 0);
+      for (let cid = 0; cid <= maxCID; cid++) {
+        if (this.widths[cid] != null) {
+          cidSetBuffer[Math.floor(cid / 8)] |= 0x80 >> cid % 8;
+        }
+      }
       const CIDSetRef = this.document.ref();
-      CIDSetRef.write(CIDSet);
+      CIDSetRef.write(cidSetBuffer);
       CIDSetRef.end();
 
       descriptor.data.CIDSet = CIDSetRef;

tests/unit/pdfa1.spec.js

@@ -106,4 +106,41 @@ describe('PDF/A-1', () => {
 
     expect(fontDescriptor).toContain('/CIDSet');
   });
+
+  test('CIDSet correctly identifies all glyphs in the subset', () => {
+    let options = {
+      autoFirstPage: false,
+      compress: false,
+      pdfVersion: '1.4',
+      subset: 'PDF/A-1a',
+    };
+    let doc = new PDFDocument(options);
+    const data = logData(doc);
+    doc.addPage();
+    doc.registerFont('Roboto', 'tests/fonts/Roboto-Regular.ttf');
+    doc.font('Roboto');
+    doc.text('Text');
+    const widths = doc._font.widths.slice();
+    doc.end();
+
+    const maxCID = widths.length - 1;
+    const CIDSet = Buffer.alloc(Math.ceil((maxCID + 1) / 8), 0);
+    for (let cid = 0; cid <= maxCID; cid++) {
+      if (widths[cid] != null) {
+        CIDSet[Math.floor(cid / 8)] |= 0x80 >> cid % 8;
+      }
+    }
+
+    let found = false;
+    for (let i = 0; i < data.length - 1; i++) {
+      if (data[i] === 'stream' && data[i + 1] instanceof Buffer) {
+        if (data[i + 1].equals(CIDSet)) {
+          found = true;
+          break;
+        }
+      }
+    }
+
+    expect(found).toBe(true);
+  });
 });